WO2025114270A1

WO2025114270A1 - A novel aerosol-generating element for use in an aerosol-generating article or system

Info

Publication number: WO2025114270A1
Application number: PCT/EP2024/083592
Authority: WO
Inventors: Laure Marie Catherine DUPUITS; Jérôme Jean-Yves GIRARD; Laurent Serge LAVANANT; Özgür ÖZSUN
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-11-27
Filing date: 2024-11-26
Publication date: 2025-06-05
Anticipated expiration: 2026-05-27

Abstract

An aerosol-generating element (10) for use in an aerosol-generating article (100) or system (200), the element comprising: a solid continuous matrix structure; a solid porous substrate comprising activated carbon dispersed and an aerosol-generating formulation, both dispersed within the solid continuous matrix structure. The aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element, a portion of the aerosol-generating formulation being sorbed in the solid porous substrate. The solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers. The aerosol-generating formulation comprises a polyhydric alcohol, a polyhydric alcohol content in the aerosol-generating formulation accounting for at least 40 percent by weight based on the total weight of the aerosol-generating element. The activated carbon content accounts for at least 5 percent by weight based on the total weight of the aerosol-generating element.

Description

A NOVEL AEROSOL-GENERATING ELEMENT FOR USE IN AN AEROSOLGENERATING ARTICLE OR SYSTEM

The present invention relates to an aerosol-generating element which finds particular use in an aerosol-generating article or system. The present invention further relates to an aerosol-generating article or system comprising such an aerosol-generating element.

Aerosol-generating articles in which an aerosol-generating substrate, such as a tobaccocontaining substrate, is heated rather than combusted, are known in the art. Typically in such articles an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

A number of prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosolgenerating devices in which an aerosol is generated by the transfer of heat from one or more electrical heater elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article.

Substrates for heated aerosol-generating articles have, in the past, often been produced using randomly oriented shreds, strands, or strips of tobacco material. As an alternative, rods for heated aerosol-generating articles formed from gathered sheets of tobacco material have been disclosed, by way of example, in international patent application WO 2012/164009.

International patent application WO 2011/101164 discloses alternative rods for heated aerosol-generating articles formed from strands of homogenised tobacco material, which may be formed by casting, rolling, calendering or extruding a mixture comprising particulate tobacco and at least one aerosol former to form a sheet of homogenised tobacco material. In alternative embodiments, the rods of WO 2011/101164 may be formed from strands of homogenised tobacco material obtained by extruding a mixture comprising particulate tobacco and at least one aerosol former to form continuous lengths of homogenised tobacco material.

Substrates for heated aerosol-generating articles typically further comprise an aerosol former, that is, a compound or mixture of compounds that, in use, facilitates formation of the aerosol and that preferably is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-formers include, but are not limited to: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1 ,3- butanediol and glycerin; esters of polyhydric alcohols, such as glycerin mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Alternative forms of substrates comprising nicotine have also been disclosed. By way of example, liquid nicotine compositions, often referred to as e-liquids, have been proposed. Aerosol-generating devices for heating similar liquid substrates typically include a reservoir for storing the liquid substrate and a wicking element configured to transport liquid substrate from the reservoir to a heat source, which may, for example, be in the form of a coiled electrically resistive filament. Particular care may be required in the manufacture of the reservoirs holding the liquid substrate in order to prevent undesirable leakages.

It has also been previously proposed to provide an encapsulated nicotine formulation for use as an aerosol-generating substrate. However, the encapsulation of nicotine formulations has been found to be challenging. One of the reasons for this is the preference for including in the nicotine formulation hydrophilic aerosol formers, such as glycerin and propylene glycol, which makes it difficult to use many of the most common encapsulation materials, which are also hydrophilic. With existing encapsulation techniques, it has generally been found that such a high level of the hydrophilic encapsulation material is required in order to produce a stable product that an insufficient payload of the nicotine formulation is ultimately provided.

Whilst hydrophobic encapsulation materials are available, such materials often need to be processed at relatively high temperature, which risks the degradation of the nicotine formulation during manufacture. During use, the temperatures required to generate an aerosol from the nicotine formulation may be sufficiently high to cause degradation of the hydrophobic encapsulation material. This may result in the release of undesirable compounds into the resultant aerosol, which may have an adverse impact on the sensory profile of the aerosol.

Attempts have also been made at providing beads wherein a liquid, nicotine-containing aerosol-generating formulation is encapsulated within a polymeric matrix, such as an alginate shell. This approach has enabled the provision of beads the size and shape of which may advantageously be controlled by adjusting certain parameters during manufacturing. However, the beads so obtained often display an undesirable tendency to stick to one another, which makes their handling generally difficult, and may cause issues if several beads are to be provided in a single aerosol-generating article. Further, exposure of the beads so obtained to heat during use appears at times to cause a significant shrinkage of the beads.

Thus, it would be desirable to provide an alternative, novel encapsulated aerosolgenerating formulations, such as for example an aerosol-generating element encapsulating a nicotine-containing formulation, which provides an improved encapsulated substrate having increased stability and minimal leakage of the aerosol-generating formulation. It would also be desirable to provide such an aerosol-generating element that is easy to handle such as to facilitate the manufacturing and packaging of aerosol-generating articles comprising one or more of the aerosol-generating element. It would also be desirable to provide such an encapsulated aerosol-generating formulation with minimal encapsulating structure, so as to provide an efficient aerosol delivery, particularly when heated to a temperature in the range from about 150 degrees Celsius to about 300 degrees Celsius.

The present disclosure relates to an aerosol-generating element for use in an aerosolgenerating article or system.

The aerosol-generating element may comprise a solid continuous matrix structure.

The solid continuous matrix structure may be a polymer matrix comprising one or more matrix-forming polymers.

The aerosol-generating element may comprise an aerosol-generating formulation dispersed within the solid continuous matrix structure.

The aerosol-generating formulation dispersed within the solid continuous matrix structure may comprise a polyhydric alcohol.

The aerosol-generating formulation may be trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element.

A polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure may account for at least 40 percent by weight based on the total weight of the aerosol-generating element.

The aerosol-generating element may further comprise a solid porous substrate also dispersed within the solid continuous matrix structure.

The solid porous substrate may comprise activated carbon.

The activated carbon content may account for at least 5 percent by weight based on the total weight of the aerosol-generating element.

A portion of the aerosol-generating formulation may be sorbed in the solid porous substrate.

According to a first aspect of the present invention, there is provided an aerosolgenerating element for use in an aerosol-generating article or system. The aerosol-generating element comprises a solid continuous matrix structure; a solid porous substrate dispersed within the solid continuous matrix structure, the solid porous substrate comprising activated carbon; and an aerosol-generating formulation also dispersed within the solid continuous matrix structure, wherein the aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element, a portion of the aerosol-generating formulation being sorbed in the solid porous substrate. The solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers. The aerosol-generating formulation dispersed within the solid continuous matrix structure comprises a polyhydric alcohol, a polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounting for at least 40 percent by weight based on the total weight of the aerosol-generating element. The activated carbon content accounts for at least 5 percent by weight based on the total weight of the aerosol-generating element.

An aerosol-generating element according to the present invention may be used in an aerosol-generating article. For example, an aerosol-generating article may comprise a plurality of aerosol-generating elements according to the first aspect of the present invention. In more detail, the aerosol-generating article may comprise an internal cavity and a plurality of aerosol-generating elements according to the first aspect of the present invention located within the internal cavity. A thickness of the aerosol-generating article may be less than 50 percent of both a length and a width of the aerosol-generating article.

According to a second aspect of the present invention, there is provided an aerosolgenerating article comprising an aerosol-generating element according to the first aspect of the present invention. The aerosol-generating article further comprises a downstream section downstream of the aerosol-generating element. The downstream section comprises an aerosol-cooling element. The aerosol-cooling element comprises a hollow tubular element and a mouthpiece element downstream of the aerosol-cooling element.

According to a third aspect of the present invention, there is provided an aerosolgenerating system for producing an inhalable aerosol. The aerosol-generating system comprises an aerosol-generating article according to the second aspect of the present invention, and an aerosol-generating device comprising a heating arrangement.

According to a fourth aspect of the present invention, there is provided a cartridge for an aerosol-generating system. The cartridge comprises an aerosol-generating element according to the first aspect of the present invention and a heating arrangement. The heating arrangement comprises an electrical heating element arranged to heat at least a portion of the aerosol-generating element to generate an aerosol, and at least one cartridge electrical contact arranged to engage with corresponding at least one device electrical contact of an aerosol-generating device.

According to a fifth aspect of the present invention, there is provided an aerosolgenerating system for producing an inhalable aerosol. The aerosol-generating system comprises a cartridge according to the fourth aspect of the present invention, and an aerosolgenerating device. The aerosol-generating device comprising a power supply and at least one device electrical contact.

The term “aerosol-generating article” is used herein with reference to the invention to describe an article wherein an aerosol-generating substrate is heated to produce and deliver an aerosol to a consumer. As used herein, the term “aerosol-generating substrate” denotes a substrate capable of releasing volatile compounds upon heating to generate an aerosol.

The term “aerosol-generating element” is used herein with reference to the invention to describe a discrete, self-standing aerosol-generating substrate element capable of releasing volatile compounds upon heating to generate an aerosol. An aerosol-generating element in accordance with the present invention may find use as an aerosol-generating substrate of an aerosol-generating article.

The aerosol generated from the aerosol-generating formulation of aerosol-generating elements described herein is a dispersion of solid particles or liquid droplets (or a combination of solid particles and liquid droplets) in a gas. The aerosol may be visible or invisible and may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles or liquid droplets or a combination of solid particles and liquid droplets.

A conventional cigarette is lit when a user applies a source of ignition to one end of the cigarette and draws air through the other end. The localised heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite, and the resulting combustion generates an inhalable smoke. By contrast, in heated aerosolgenerating articles, an aerosol is generated by heating a flavour generating substrate, such as, for example, a tobacco-based substrate or a substrate containing an aerosol-former and a flavouring. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separate aerosol forming material.

For example, aerosol-generating articles according to the invention may find particular application in aerosol-generating systems comprising an electrically heated aerosolgenerating device having an internal heater which is adapted to supply heat to one or more discrete aerosol-generating substrate elements. As used herein with reference to the present invention, the term “aerosol-generating device” is used to described a device comprising a heater element that interacts with one or more aerosol-generating elements in accordance with the invention to produce an aerosol. During use, volatile compounds are released from the aerosol-generating element or elements by heat transfer and entrained in air drawn through the aerosol-generating article. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer.

Substrates for heated aerosol-generating articles typically comprise an “aerosol former”, that is, a compound or mixture of compounds that, in use, facilitates formation of the aerosol, and that preferably is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-formers include: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1 ,3-butanediol and glycerin; esters of polyhydric alcohols, such as glycerin mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The polyhydric alcohol in the aerosol-generating article of the invention is also an aerosol former within the meaning set out above.

As used herein with reference to the present invention, the term “aerosol-generating formulation” refers to a formulation comprising a plurality of aerosol-generating formulation components, which upon heating of the aerosol-generating element will volatilise to produce an aerosol.

As used herein with reference to the present invention, the term “matrix-forming polymer” refers to an encapsulation material in the form of a polymer which is capable of producing a three-dimensional polymer matrix as a result of cross-linking when the matrixforming polymer is brought into contact with a cross-linking solution of multivalent cations. The resultant polymer matrix is capable of trapping and retaining the aerosol-generating formulation within its cross-linked structure. The nature of the cross-linked polymer matrix will be discussed in more detail below.

As briefly described above, in contrast with existing aerosol-generating elements, an aerosol-generating element in accordance with the present invention comprises a solid continuous matrix structure (for example, an alginate matrix), a solid porous substrate dispersed within the solid continuous matrix structure, wherein the solid porous substrate comprises activated carbon, and an aerosol-generating formulation dispersed within the solid continuous matrix structure.

In more detail, the aerosol-generating formulation is trapped within the solid continuous matrix structure and can be released from the solid continuous matrix structure upon heating of the aerosol-generating element to a predetermined temperature. Additionally, a portion of the aerosol-generating formulation is sorbed in the solid porous substrate.

Without wishing to be bound by theory, it is understood that in an aerosol-generating element in accordance with the present invention a three-dimensional polymeric matrix structure is formed by cross-linking, and aerosol-generating formulation is retained within the polymeric matrix structure as well as sorbed within the solid porous substrate comprising activated carbon which is also dispersed within the polymeric matrix structure. This is, in particular, in contrast with existing core/shell structures wherein a content of the core is released upon rupturing the shell.

In an aerosol-generating element in accordance with the first aspect of the present invention the solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers. Further, the aerosol-generating formulation dispersed within the solid continuous matrix structure comprises a polyhydric alcohol, and a polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 40 percent by weight based on the total weight of the aerosolgenerating element. In turn, the activated carbon content accounts for at least 5 percent by weight based on the total weight of the aerosol-generating element.

Advantageously, the invention provides an aerosol-generating formulation in encapsulated form that has a significantly lower content of encapsulation material (corresponding to the one or more matrix-forming polymers of the solid continuous matrix structure) compared with previously available substrates. As such, the levels of the aerosolgenerating formulation components, such as the polyhydric alcohol and any other further ingredient, can advantageously be maximised within the aerosol-generating element. The reduction in the proportion of encapsulation material required also enables a more efficient generation of aerosol upon heating, since less of the heat supplied to the aerosol-generating element is used for increasing the temperature of the encapsulation material.

The polymer-based solid continuous matrix of aerosol-generating articles in accordance with the present invention provides an inert encapsulation structure for retaining and immobilising the aerosol-generating formulation, which is stable upon heating of the aerosolgenerating element during use.

Additionally, at least a fraction of the aerosol-generating formulation retained within the solid continuous matrix structure is in effect sorbed within the solid porous substrate which is, in turn, dispersed within the solid continuous matrix structure.

The inventors have found that, when heated to temperatures in the range from 150 degrees Celsius to 350 degrees Celsius, aerosol-generating elements in accordance with the present invention release an aerosol as they undergo a weight loss. This weight loss is not, however, accompanied by an equally significant shrinkage of the aerosol-generating element. Without wishing to be bound by theory, it is understood that, upon heating, volatile components of the aerosol-generating formulation originally sorbed in the solid porous substrate are desorbed and released, whilst at the same time any components of the aerosol-generating formulation originally dispersed and trapped within the solid continuous matrix structure without being sorbed in the solid porous substrate are substantially vaporised and released.

On the other hand, the solid continuous matrix essentially retains its 3D structure around the solid porous substrate, which is substantially unaffected when heated to temperatures in the range from 150 degrees Celsius to 350 degrees Celsius (significant thermal decomposition of activated carbon is generally associated with higher temperatures, such as in the range from 400 degrees Celsius to 600 degrees Celsius). As such, the encapsulation of the aerosolgenerating formulation within an aerosol-generating element according to the present invention advantageously provides minimal or no adverse effects on the sensory profile of the aerosol generated upon heating. The aerosol-generating element of the present invention has been found to advantageously provide a controlled delivery of aerosol. Furthermore, the aerosol delivery profile can be readily adjusted by adjusting parameters of the aerosol-generating element such as the size, shape, structure and formulation of the aerosol-generating element.

The invention advantageously provides an aerosol-generating element that is in the form of a discrete, self-standing solid object which is sufficiently stable and robust that it can readily be processed and introduced into an aerosol-generating article using existing methods and techniques.

Further, aerosol-generating elements in accordance with the present invention can be prepared by a cost-effective method that can be carried out with existing equipment, as will become apparent from the following description thereof. In addition, aerosol-generating elements in accordance with the present invention can be prepared by a method that can be easily incorporated into existing production lines for the manufacture of aerosol-generating articles. Aerosol-generating elements in accordance with the present invention have been found to be less sticky than aerosol-generating elements not including activated carbon, and this makes them generally easier to handle and provides benefits when it comes to incorporating the aerosol-generating elements into an aerosol-generating article or in view of their direct use with an aerosol-generating device.

Aerosol-generating elements in accordance with the present invention may be prepared from a matrix precursor solution and components of an aerosol-generating formulation. By way of example, in a method of manufacturing an aerosol-generating element in accordance with the invention, a matrix precursor solution may be provided that comprises a matrixforming polymer (for example, alginate) in water. For example, the matrix precursor solution may comprise at least about 35 percent by weight of water or at least about 40 percent by weight of water. This level of water ensures that the matrix-forming polymer is sufficiently dissolved so that a homogeneous solution is provided.

The matrix-forming polymer may be a single polymer or a combination of two or more polymers, wherein the one or more polymers are capable of forming a cross-linked matrix through an ionotropic gelation mechanism in a cross-linking solution of multivalent cations. The cross-linking of the matrix-forming polymer is achieved through reaction of the polymer with multivalent cations in the cross-linking solution, which form salt bridges to cross-link the polymer molecules.

Suitable matrix-forming polymers would be known to the skilled person, and include, but are not limited to, alginate, pectin, hydroxyethylmethacryate (HEMA), N-(2-hydroxy propyl)methacrylate (HPMA), N-vinyl-2-pyrrolidone (NVP), N-isopropylacrylamide (NIPAMM), vinyl acetate (VAc), acrylic acid (AA), methacrylic acid (MAA), polyethylene glycol acrylate/methacrylate (PEGA/PEGMA) and polyethylene glycol diacrylate/dimethacrylate, (PEGDA/PEGDMA).

Preferably, the matrix-forming polymer comprises one or more polysaccharides, such as alginate or pectin, or a combination thereof. Polysaccharides are particularly suitable for use in the present invention, since they can be made water insoluble and heat stable through cross-linking, and are tasteless. There is therefore no adverse impact on the sensory properties of the aerosol generated from the aerosol-generating element. Alternative matrixforming polymers suitable for use in methods according to the invention include but are not limited to chitosan, fibrin, collagen, gelatin, hyaluronic acid, dextran and combinations thereof.

In preferred embodiments, the matrix-forming polymer is alginate and the solid continuous matrix structure is an alginate matrix. As mentioned briefly above, alginate is a polymer that is capable of forming a cross-linked matrix through an ionotropic gelation mechanism in a cross-linking solution of multivalent cations. The cross-linking of the alginate is achieved through reaction of the alginate with multivalent cations in the cross-linking solution, which form salt bridges to cross-link the alginate molecules. Alginate has been found to be particularly suitable for use in the present invention, as it can be made water insoluble and heat stable through cross-linking, and is tasteless. There is therefore no adverse impact on the sensory properties of the aerosol generated from the aerosol-generating element.

To manufacture aerosol-generating elements in accordance with the present invention, a plurality of aerosol-generating formulation components may be added to a matrix precursor solution to form an aerosol-generating solution, wherein the aerosol-generating formulation components may include at least one alkaloid compound and a polyhydric alcohol. As used herein when describing a method of preparing aerosol-generating elements in accordance with the invention, the term “aerosol-generating solution” denotes a solution of the aerosolgenerating formulation components and the matrix precursors, in an appropriate solvent.

It may be desirable to control the viscosity of aerosol-generating solution. This may include controlling the viscosity of the matrix polymer solution as the aerosol-generating formulation components are added. For example, depending upon the technique used for producing the discrete portion of the aerosol-generating solution in the subsequent step of the method, it may be preferable to provide the aerosol-generating solution with a viscosity within a specific range. Different techniques are likely to be facilitated by different viscosity solutions and an appropriate viscosity should therefore be determined depending upon the technique used.

By way of example, when the discrete portion of the aerosol-generating solution is produced in a gravitational dripping process, the viscosity of the solution is preferably retained below about 5000 mPa.s. (milliPascal-seconds). This enables droplets of the aerosolgenerating solution to be formed under gravity and also allows the beads to reach a stable shape in the cross-linking solution before the cross-linking hardens the solution and fixes the final shape of the aerosol-generating element.

In particular, the inventors have found that the viscosity of the aerosol-generating solution may have an impact on how easily the shape of the aerosol-generating elements being formed can be controlled. For example, when forming spherical or substantially spherical having an equivalent diameter of 3 millimetres or more, there appears to be a particular benefit in controlling the viscosity of the aerosol-generating solution as described above, as this facilitates forming aerosol-generating elements with a desired sphericity.

In certain cases, in order to control the viscosity of the aerosol-generating solution it may be preferably to control the pH of the matrix polymer solution whilst the aerosol-generating formulation components are being added. This is because for some matrix polymer solutions, the pH may affect the viscosity. For example, in embodiments of the invention in which the matrix-forming polymer comprises alginate, it is preferable to retain the pH of the solution above pH4. This is intended to avoid any gelling of the alginate, which may occur at pH levels below pH4, for example, due to hydrogen bonding. Such gelling at a low pH would cause an undesirable increase in the viscosity of the aerosol-generating solution, which would make it difficult to use certain techniques such as gravitational dripping, in order to form the aerosolgenerating element.

Alternatively or in addition, the viscosity of the aerosol-generating solution may be controlled by adjusting the concentration of the solution. For example, the proportion of water in the aerosol-generating solution may be adjusted in order to adjust the viscosity. Preferably, the aerosol-generating solution comprises at least about 35 percent by weight of water in order to maintain a suitable viscosity. Particularly preferably, the aerosol-generating solution comprises between about 35 percent by weight and about 65 percent by weight of water.

In a second step, a discrete portion of the aerosol-generating solution may be formed.

In a third step, the formed discrete portion of the aerosol-generating solution may be added to a cross-linking solution of multivalent cations to cross-link the matrix-forming polymer, thereby forming an aerosol-generating element having a continuous polymer matrix structure and an aerosol-generating formulation comprising the aerosol-generating components dispersed within the continuous polymer matrix. Preferred multivalent cations include calcium, iron, aluminium, manganese, copper, zinc or lanthanum. A particularly preferred salt is calcium chloride.

In certain preferred embodiments of the invention in which the aerosol-generating solution comprises an acid, the calcium salt provided in the cross-linking solution may advantageously be a salt of the same acid. For example, in embodiments in which the aerosolgenerating solution comprises lactic acid, the cross-linking solution may advantageously comprise calcium lactate. Where the aerosol-generating solution comprises nicotine, the acid in the aerosolgenerating solution forms a nicotine salt with the nicotine. The use of a calcium salt corresponding to the acid in the aerosol-generating solution therefore provides the same salt in the cross-linking solution as in the aerosol-generating solution. This, in turn, advantageously limits the diffusion of nicotine salts out of the aerosol-generating solution into the cross-linking solution during the cross-linking step. A higher concentration of the nicotine salt can therefore be retained within the aerosol-generating element. Furthermore, any potential waste of the nicotine and acid during the production of the aerosol-generating element can be reduced.

Preferably, the cross-linking solution further comprises a polyhydric alcohol, which is the same as the polyhydric alcohol selected as the aerosol-generating formulation component. The inclusion of the polyhydric alcohol in the cross-linking solution has been found to limit diffusion of the polyhydric alcohol from the aerosol-generating solution into the cross-linking solution during the cross-linking step. This advantageously enables a higher concentration of the polyhydric alcohol to be retained within the aerosol-generating element than has been previously possible.

In a fourth step, the aerosol-generating element may be removed from the cross-linking solution and dried. As described briefly above, in an aerosol-generating element in accordance with the present invention the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 80 percent by weight of a total weight of the aerosol-generating element.

As described briefly above, the solid porous substrate comprises activated carbon. The solid porous substrate may consist only of activated carbon.

As used herein with reference to the present invention, the term “activated carbon” refers to a form of carbon which is highly porous over a broad range of pore sizes, from visible cracks and crevices to cracks and crevices of molecular dimensions resulting in very high internal surface area making it ideal for adsorption uses. Activated carbon is suitably defined by ASTM D2652-11 (Reapproved 2020) Standard Terminology Relating to Activated Carbon as “a family of carbonaceous substances manufactured by processes that develop adsorptive properties”. Activation is suitably defined by ASTM D2652-11 (Reapproved 2020) as “any process whereby a substance is treated to develop adsorptive properties”. Activated carbon may be formed by the pyrolysis of organic materials.

As used herein with reference to the present invention, the term “sorb” refers to the process by which the solid porous substrate takes in and retains components of an aerosolgenerating formulation. The sorption may include one or more of adsorption and absorption. The sorption may comprise drawing components of the aerosol-generating formulation into the pores of the solid porous substrate by capillary action. The solid porous substrate may have a standard BET surface area of at least 100 metres squared per gram.

The standard BET surface area of the porous element is determined using N2 isotherms which are generated by adsorption of N2 at -196 degrees Celsius and 0 degrees Celsius using ASAP 2020 from Micromeritics and Autosorb-6B from Quantachrome equipment. The samples are then outgassed at 250 degrees Celsius for 4 hours. The N2 adsorption data may then be used to calculate the apparent BET surface area (SBET) by application of the BET equation.

Preferably, the solid porous substrate has a standard BET surface area of at least 150 metres squared per gram. More preferably, the solid porous substrate has a standard BET surface area of at least 200 metres squared per gram. Even more preferably, the solid porous substrate has a standard BET surface area of at least 250 metres squared per gram.

The solid porous substrate may have a standard BET surface area of less than or equal to 600 metres squared per gram. Preferably, the solid porous substrate has a standard BET surface area of less than or equal to 550 metres squared per gram. More preferably, the solid porous substrate has a standard BET surface area of less than or equal to 500 metres squared per gram. Even more preferably, the solid porous substrate has a standard BET surface area of less than or equal to 450 metres squared per gram.

Preferably, the solid porous substrate has a standard BET surface area from 100 metres squared per gram to 600 metres squared per gram. In some embodiments, the solid porous substrate has a standard BET surface area from 100 metres squared per gram to 550 metres squared per gram, preferably from 100 metres squared per gram to 500 metres squared per gram, more preferably from 100 metres squared per gram to 450 metres squared per gram. In other embodiments, the solid porous substrate has a standard BET surface area from 150 metres squared per gram to 550 metres squared per gram, preferably from 150 metres squared per gram to 500 metres squared per gram, more preferably from 150 metres squared per gram to 450 metres squared per gram. In further embodiments, the solid porous substrate has a standard BET surface area from 200 metres squared per gram to 550 metres squared per gram, preferably from 200 metres squared per gram to 500 metres squared per gram, more preferably from 200 metres squared per gram to 450 metres squared per gram. In yet further embodiments, the solid porous substrate has a standard BET surface area from 250 metres squared per gram to 550 metres squared per gram, preferably from 250 metres squared per gram to 500 metres squared per gram, more preferably from 250 metres squared per gram to 450 metres squared per gram.

The inventors have identified that a solid porous substrate for including in an aerosolgenerating element according to the first aspect of the invention exhibits predictable and advantageous desorption properties during use of the aerosol-generating element, such as in an aerosol-generating system. As described in more detail below, the inventors have identified that the provision of a solid porous substrate formed from activated carbon and having a standard BET surface area of between 100 metres squared per gram and 600 metres squared per gram advantageously results in a single desorption peak upon heating of the solid porous substrate as part of the aerosol-generating element. In this way, the user experience is more consistent. This is in contrast to aerosol-generating substrate reservoirs not having these characteristics, which may exhibit multiple desorption peaks resulting in inconsistent and fluctuating aerosol delivery during the use of the aerosol-generating element. This degrades the user experience and is therefore undesirable.

In addition, the inventors of the present invention have identified that a solid porous substrate formed from activated carbon and having a standard BET surface area of between 100 metres squared per gram and 600 metres squared per gram may be advantageously able to retain a sufficient volume of aerosol-generating formulation per gram of porous substrate. Such a solid porous substrate may also be able to retain the aerosol-generating formulation such that leakage of aerosol-generating formulation out of the aerosol-generating element - and, during use, out of the aerosol-generating system - is reduced or prevented. The inventors have identified that such a solid porous substrate comprising activated carbon and having a standard BET surface area within the ranges described above is able to sorb aerosolgenerating formulation by capillary action which draws the components of the aerosolgenerating formulation into the pores of the porous substrate.

The solid porous substrate may have any pore volume. For example, the solid porous substrate may have a pore volume measured using adsorption isotherm of carbon dioxide VDR (CO2) of at least 0.05 cubic centimetres per gram. To generate the adsorption isotherm of carbon dioxide, CO2 is sorbed on the sample at -196 degrees Celsius and 0 degrees Celsius using ASAP 2020 from Micromeritics and Autosorb-6B from Quantachrome equipment. The samples are then outgassed at 250 degrees Celsius for 4 hours. The CO2 adsorption data may then be used to calculate the VDR (CO2) by application of the Dubinin-Radushkevich equation.

For example, the solid porous substrate may have a pore volume measured using adsorption isotherm of carbon dioxide DR (CO2) of at least 0.1 cubic centimetres per gram, at least 0.15 cubic centimetres per gram, or at least 0.2 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using adsorption isotherm of carbon dioxide VDR (CO2) of no more than 0.35 cubic centimetres per gram.

For example, the solid porous substrate may have a pore volume measured using adsorption isotherm of carbon dioxide VDR (CO2) of no more than 0.3 cubic centimetres per gram, or no more than 0.25 cubic centimetres per gram. The solid porous substrate may have a pore volume measured using adsorption isotherm of carbon dioxide VDR (CO2) of between 0.05 cubic centimetres per gram and 0.35 cubic centimetres per gram, between 0.1 cubic centimetres per gram and 0.3 cubic centimetres per gram, or between 0.15 cubic centimetres per gram and 0.25 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using adsorption isotherm of carbon dioxide VDR (CO2) of between 0.1 cubic centimetres per gram and 0.25 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using adsorption isotherm of nitrogen DR (N2) of at least 0.05 cubic centimetres per gram. To generate the adsorption isotherm of nitrogen, N2 is sorbed on the sample at -196 degrees Celsius and 0 degrees Celsius using ASAP 2020 from Micromeritics and Autosorb-6B from Quantachrome equipment. The samples are then outgassed at 250 degrees Celsius for 4 hours. The N2 adsorption data may then be used to calculate the VDR (N2) by application of the Dubinin- Radushkevich equation.

For example, the solid porous substrate may have a pore volume measured using adsorption isotherm of nitrogen VDR (N2) of at least 0.1 cubic centimetres per gram, at least 0.15 cubic centimetres per gram, or at least 0.2 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using adsorption isotherm of nitrogen VDR (N2) of no more than 0.35 cubic centimetres per gram.

For example, the solid porous substrate may have a pore volume measured using adsorption isotherm of nitrogen VDR (N2) of no more than 0.3 cubic centimetres per gram, or no more than 0.25 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using adsorption isotherm of nitrogen VDR (N2) of between 0.05 cubic centimetres per gram and 0.35 cubic centimetres per gram, between 0.1 cubic centimetres per gram and 0.3 cubic centimetres per gram, or between 0.15 cubic centimetres per gram and 0.25 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using adsorption isotherm of nitrogen VDR (N2) of between 0.1 cubic centimetres per gram and 0.25 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using V_meso (N2) of at least 0.01 cubic centimetres per gram. The pore volume assessment using V_meso (N2) is used to provide an indication of the volume of pores having a diameter of between about 2 nanometres and 7.5 nanometres. V_meso (N2) may be calculated as the difference between the volume of N2 sorbed as a liquid at P/P0 = 0.7 and P/P0 = 0.2. “P” corresponds to the partial vapour pressure of adsorbate gas in equilibrium and “P0” corresponds to the saturated vapour pressure of adsorbate gas. For example, the solid porous substrate may have a pore volume measured using Vmeso (N2) of at least 0.02 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using V_meso (N2) of no more than 0.15 cubic centimetres per gram. For example, the solid porous substrate may have a pore volume measured using V_meso (N2) of at least 0.08 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using V_meso (N2) of between 0.01 cubic centimetres per gram and 0.15 cubic centimetres per gram, or between 0.02 cubic centimetres per gram and 0.08 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using V_meso (Hg) of at least 0.001 cubic centimetres per gram. The pore volume assessment using V_meso (Hg) is used to provide an indication of the volume of pores having a diameter between 7.5 nanometres and 50 nanometres. Hg intrusion porosimetry may be used to determine the pore volume. Hg porosimetry data may be obtained using a Poremaster-60 GT from Quantachrome Instruments.

For example, the solid porous substrate may have a pore volume measured using Vmeso (Hg) of at least 0.005 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using V_meso (Hg) of no more than 0.1 cubic centimetres per gram. For example, the solid porous substrate may have a pore volume measured using V_meso (Hg) of at least 0.05 cubic centimetres per gram.

The solid porous substrate may have a pore volume measured using V_meso (Hg) of between 0.001 cubic centimetres per gram and 0.1 cubic centimetres per gram, or between 0.005 cubic centimetres per gram and 0.05 cubic centimetres per gram.

The solid porous substrate may have a total mesopore volume (VT_meso) of at least 0.01 cubic centimetres per gram.

As used herein with reference to the present invention, the term “mesopore” refers to pores of the solid porous substrate having a pore diameter of between 2 nanometres and 50 nanometres. The total mesopore volume is the sum of the volumes measured using V_meso (N₂) and Vmeso (Hg). In other words, VT_meso = V_meso (N₂) + V_meso (Hg).

The solid porous substrate may have a total mesopore volume (VTmeso) of at least 0.02 cubic centimetres per gram.

The solid porous substrate may have a total mesopore volume (VTmeso) of no more than 1 cubic centimetre per gram. For example, the solid porous substrate may have a total mesopore volume (VTmeso) of no more than 0.1 cubic centimetres per gram.

The solid porous substrate may have a total mesopore volume (VTmeso) of between 0.01 cubic centimetres per gram and 1 cubic centimetre per gram, or between 0.02 cubic centimetres per gram and 0.1 cubic centimetres per gram. The solid porous substrate may have a total macropore volume (V_macro) of at least 0.1 cubic centimetres per gram. The pore volume assessment using V_macro is used to provide an indication of the volume of pores having a diameter greater than 50 nanometres. Hg intrusion porosimetry may be used to determine the pore volume. Hg porosimetry data may be obtained using a Poremaster-60 GT from Quantachrome Instruments.

As used herein with reference to the present invention, the term “macropore” refers to pores of the solid porous substrate having a pore diameter of greater than 50 nanometres.

The solid porous substrate may have a total mesopore volume (V_macro) of at least 0.5 cubic centimetres per gram.

The solid porous substrate may have a total mesopore volume (V_macro) of no more than 5 cubic centimetre per gram. For example, the solid porous substrate may have a total mesopore volume (V_macro) of no more than 4 cubic centimetres per gram.

The solid porous substrate may have a total mesopore volume (V_macro) of between 0.1 cubic centimetres per gram and 5 cubic centimetres per gram, or between 0.5 cubic centimetres per gram and 4 cubic centimetres per gram.

The solid porous substrate may have a total pore volume (VT) of at least 0.05 cubic centimetres per gram.

The total pore volume (VT) refers to the sum of the pore volumes of all of the pores in the solid porous substrate per unit mass. The total pore volume (VT) is calculated as the sum of the volumes using VDR (N2), VT_meso, and V_macro. In other words, VT = VDR (N2) + VT_meso + Vm_acro.

The solid porous substrate may have a total pore volume (VT) of at least 1 cubic centimetre per gram.

The solid porous substrate may have a total pore volume (VT) of no more than 3 cubic centimetres per gram. For example, the solid porous substrate may have a total pore volume (VT) of no more than 2 cubic centimetres per gram.

The solid porous substrate may have a total pore volume (VT) of between 0.05 cubic centimetres per gram and 3 cubic centimetres per gram, or between 1 cubic centimetre per gram and 2 cubic centimetres per gram.

The porous element may have a surface concentration of oxygen (Otot_ai) of at least 3 percent by weight when measured using temperature-programmed desorption (TPD).

The surface concentration of oxygen (Otot_ai) is the total weight percentage of surface oxygen as determined by temperature-programmed desorption (TPD) carried out using a differential scanning calirometer-thermogravimetric analyser (DSC-TGA TA, Simultaneous SDT 2960) coupled to a mass spectrometer (Balzers, OmniStar). The surface concentration of oxygen (Otot_ai) is related to the evolution of oxygen-containing species during the TPD experiment. These species may include CO2 and CO. The inventors have identified that the provision of a solid porous substrate with a surface concentration of oxygen (Ototai) of at least 3 percent by weight may improve the desorption properties of the solid porous substrate. The surface concentration of oxygen is a feature of the activated carbon solid porous substrate which may be tailored during the processing of the solid porous substrate and during manufacturing of the aerosol-generating element.

For example, the solid porous substrate may have a surface concentration of oxygen (Ototai) of at least 4 percent, at least 5 percent, or at least 6 percent by weight when measured using temperature-programmed desorption (TPD).

The solid porous substrate may have a surface concentration of oxygen (Ototai) of no more than 20 percent when measured using temperature-programmed desorption (TPD).

For example, the solid porous substrate may have a surface concentration of oxygen (Ototai) of no more than 18 percent, no more than 14 percent, or no more than 10 percent by weight when measured using temperature-programmed desorption (TPD).

For example, the solid porous substrate may have a surface concentration of oxygen (Ototai) of between 3 percent and 20 percent by weight, between 4 percent and 18 percent by weight, between 5 percent and 14 percent by weight, between 6 percent and 10 percent by weight when measured using temperature-programmed desorption (TPD).

The solid porous substrate may have a surface concentration of oxygen (Ototai) of between 8 percent and 17 percent by weight when measured using temperature-programmed desorption (TPD).

The total amount of CO2 and CO evolved from the solid porous substrate during temperature-programmed desorption (TPD) may be at least 1500 micromoles per gram.

The total amount of CO2 and CO evolved from the solid porous substrate during temperature-programmed desorption (TPD) corresponds to the sum of the amount of CO2 evolved and the amount to CO evolved during a temperature-programmed desorption (TPD) test carried out using a differential scanning calirometer-thermogravimetric analyser (DSC- TGA TA, Simultaneous SDT 2960) coupled to a mass spectrometer (Balzers, OmniStar).

The inventors have identified that the total amount of CO2 and CO evolved provides an indication of the surface oxygen concentration of the solid porous substrate. The higher the total amount of CO2 and CO evolved during a TPD test, the higher the surface oxygen concentration of the solid porous substrate. As a result, it has been found that solid porous substrates which evolve at least 1500 micromoles per gram of CO2 and CO during a TPD test advantageously result in a single desorption peak during the use of the aerosol-generating system. In this way, the user experience is more consistent. The total amount of CO2 and CO evolved from the solid porous substrate during temperature-programmed desorption (TPD) may be at least 2000 micromoles per gram or at least 2500 micromoles per gram.

The total amount of CO2 and CO evolved from the solid porous substrate during temperature-programmed desorption (TPD) may be no more than 7000 micromoles per gram or no more than 6000 micromoles per gram.

The ratio of CO2 to CO evolved from the solid porous substrate during temperatureprogrammed desorption (TPD) may be at least 0.2.

The inventors have identified that the CO2/CO ratio is an important surface chemistry parameter. During a temperature-programmed desorption (TPD) test, thermal temperature degradation of surface oxygen on the activated carbon solid porous substrate leads to the evolution of CO2 and CO gas. CO2 is typically evolved by the decomposition of functional groups which are acidic in character. CO is typically evolved by the decomposition of functional groups which are basic in character. Accordingly, a CO2/CO ratio of about 1 indicates a neutral surface chemistry.

The ratio of CO2 to CO evolved from the solid porous substrate during temperatureprogrammed desorption (TPD) may be at least 0.4.

The ratio of CO2 to CO evolved from the solid porous substrate during temperatureprogrammed desorption (TPD) may be no more than 1.5. For example, the ratio of CO2 to CO evolved from the solid porous substrate during temperature-programmed desorption (TPD) may be no more than 1 .2.

The ratio of CO2 to CO evolved from the solid porous substrate during temperatureprogrammed desorption (TPD) may be between 0.2 and 1.5, or between 0.4 and 1.2.

The ratio of CO2 to CO evolved from the solid porous substrate during temperatureprogrammed desorption (TPD) may be about 1 .

As described above, the provision of an aerosol-generating substrate reservoir comprising a solid porous substrate having the parameters of the present invention may advantageously provide a single desorption peak during the use of the aerosol-generating system.

The solid porous substrate may exhibit a single derivative TG (DTG) peak. The single derivative TG peak is the differential of the thermogravimetric (TG) curve.

The single derivative TG (DTG) peak may be over 160 degrees Celsius. For example, the single derivative TG (DTG) peak may be over 180 degrees Celsius, over 200 degrees Celsius, or over 220 degrees Celsius.

The single derivative TG (DTG) peak may be no higher than 300 degrees Celsius. For example, the single derivative TG (DTG) peak may be no higher than 280 degrees Celsius, no higher than 260 degrees Celsius, or no higher than 240 degrees Celsius. The single derivative TG (DTG) peak may be between 160 degrees Celsius and 300 degrees Celsius, between 180 degrees Celsius and 280 degrees Celsius, between 200 degrees Celsius and 260 degrees Celsius, or between 220 degrees Celsius and 240 degrees Celsius.

The single derivative TG (DTG) peak may be between 160 degrees Celsius and 230 degrees Celsius. The single derivative TG (DTG) peak may be about 230 degrees Celsius.

As described briefly above, in aerosol-generating elements in accordance with the present invention, the activated carbon content accounts for at least 5 percent by weight based on the total weight of the aerosol-generating element. Preferably, in an aerosol-generating element according to the present invention the activated carbon content accounts for at least 10 percent by weight based on the total weight of the aerosol-generating element.

The inventors have found that a content of activated carbon accounting for at least 5 percent by weight, and preferably at least 10 percent by weight based on the total weight of the aerosol-generating element is associated with a reduction in the volume loss (shrinkage) of the aerosol-generating element during use. Further, aerosol-generating elements in accordance with the present invention containing at least 5 percent by weight of activated carbon based on the total weight of the aerosol-generating element are significantly less prone to sticking to one another compared with aerosol-generating elements having a smaller content of - or no content of - activated carbon.

More preferably, in an aerosol-generating element according to the present invention the activated carbon content accounts for at least 12 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, in an aerosol-generating element according to the present invention the activated carbon content accounts for at least 15 percent by weight based on the total weight of the aerosol-generating element.

In aerosol-generating elements in accordance with the present invention the activated carbon content may account for up to 35 percent by weight based on the total weight of the aerosol-generating element, for example up to 30 percent by weight based on the total weight of the aerosol-generating element. Without wishing to be bound by theory, it is hypothesised that higher contents of activated carbon may cause a larger fraction of the aerosol-generating formulation to be sorbed, which may be undesirable from a viewpoint of steady release of aerosol species during use. Additionally, higher contents of activated carbon may complicate the manufacturing process by which the aerosol-generating elements are obtained.

Preferably, in an aerosol-generating element according to the present invention the activated carbon content accounts for less than or equal to 25 percent by weight based on the total weight of the aerosol-generating element. More preferably, in an aerosol-generating element according to the present invention the activated carbon content accounts for less than or equal to 22 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, in an aerosol-generating element according to the present invention the activated carbon content accounts for less than or equal to 20 percent by weight based on the total weight of the aerosol-generating element.

In some embodiments, the activated carbon content accounts for from 5 percent by weight to 25 percent by weight based on the total weight of the aerosol-generating element, preferably from 10 percent by weight to 25 percent by weight based on the total weight of the aerosol-generating element, more preferably from 12 percent by weight to 25 percent by weight based on the total weight of the aerosol-generating element, even more preferably from 15 percent by weight to 25 percent by weight based on the total weight of the aerosolgenerating element.

In other embodiments, the activated carbon content accounts for from 5 percent by weight to 22 percent by weight based on the total weight of the aerosol-generating element, preferably from 10 percent by weight to 22 percent by weight based on the total weight of the aerosol-generating element, more preferably from 12 percent by weight to 22 percent by weight based on the total weight of the aerosol-generating element, even more preferably from 15 percent by weight to 22 percent by weight based on the total weight of the aerosolgenerating element.

In further embodiments, the activated carbon content accounts for from 5 percent by weight to 20 percent by weight based on the total weight of the aerosol-generating element, preferably from 10 percent by weight to 20 percent by weight based on the total weight of the aerosol-generating element, more preferably from 12 percent by weight to 20 percent by weight based on the total weight of the aerosol-generating element, even more preferably from 15 percent by weight to 20 percent by weight based on the total weight of the aerosolgenerating element.

As described briefly above, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 40 percent by weight based on the total weight of the aerosol-generating element.

Preferably, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 50 percent by weight based on the total weight of the aerosol-generating element. More preferably, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 55 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 60 percent by weight based on the total weight of the aerosol-generating element.

Preferably, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 75 percent by weight based on the total weight of the aerosol-generating element. More preferably, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosolgenerating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 70 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, in an aerosol-generating element according to the present invention, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 65 percent by weight based on the total weight of the aerosol-generating element.

In some embodiments, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for from 40 percent by weight to 75 percent by weight based on the total weight of the aerosol-generating element, preferably from 50 percent by weight to 75 percent by weight based on the total weight of the aerosol-generating element, more preferably from 55 percent by weight to 75 percent by weight based on the total weight of the aerosol-generating element, even more preferably from 60 percent by weight to 75 percent by weight based on the total weight of the aerosolgenerating element.

In other embodiments, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for from 40 percent by weight to 70 percent by weight based on the total weight of the aerosol-generating element, preferably from 50 percent by weight to 70 percent by weight based on the total weight of the aerosol-generating element, more preferably from 55 percent by weight to 70 percent by weight based on the total weight of the aerosol-generating element, even more preferably from 60 percent by weight to 70 percent by weight based on the total weight of the aerosolgenerating element.

In further embodiments, the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for from 40 percent by weight to 65 percent by weight based on the total weight of the aerosol-generating element, preferably from 50 percent by weight to 65 percent by weight based on the total weight of the aerosol-generating element, more preferably from 55 percent by weight to 65 percent by weight based on the total weight of the aerosol-generating element, even more preferably from 60 percent by weight to 65 percent by weight based on the total weight of the aerosolgenerating element. As defined above, an aerosol-generating element in accordance with the invention comprises a polyhydric alcohol as a component of the aerosol-generating formulation dispersed within the solid continuous matrix structure.

The polyhydric alcohol acts as the aerosol former of the aerosol-generating element. Polyhydric alcohols suitable for use in the aerosol-generating element include, but are not limited to, propylene glycol, triethylene glycol, 1 ,3-butanediol, and glycerin. Preferably, in an aerosol-generating element in accordance with the invention the polyhydric alcohol is selected from the group consisting of glycerin, propylene glycol, and combinations thereof. In particularly preferred embodiments the polyhydric alcohol is glycerin.

An aerosol-generating element in accordance with the present invention may comprise at least 1 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element. Preferably, the aerosol-generating element comprises at least 2 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element. More preferably, the aerosol-generating element comprises at least 3 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element.

An aerosol-generating element in accordance with the present invention may comprise up to 12 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element. Preferably, the aerosol-generating element comprises less than or equal to 10 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element. More preferably, the aerosol-generating element comprises less than or equal to 5 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element.

In some embodiments, the aerosol-generating element comprises from 1 percent by weight to 12 percent by weight, preferably from 2 percent by weight to 12 percent by weight, more preferably from 3 percent by weight to 12 percent by weight of the one or more matrixforming polymers based on the total weight of the aerosol-generating element.

In other embodiments, the aerosol-generating element comprises from 1 percent by weight to 10 percent by weight, preferably from 2 percent by weight to 10 percent by weight, more preferably from 3 percent by weight to 10 percent by weight of the one or more matrixforming polymers based on the total weight of the aerosol-generating element.

In further embodiments, the aerosol-generating element comprises from 1 percent by weight to 5 percent by weight, preferably from 2 percent by weight to 5 percent by weight, more preferably from 3 percent by weight to 5 percent by weight of the one or more matrixforming polymers based on the total weight of the aerosol-generating element.

In preferred embodiments, an aerosol-generating element in accordance with the present invention may comprise at least 1 percent by weight of alginate based on the total weight of the aerosol-generating element. Preferably, the aerosol-generating element comprises at least 2 percent by weight of alginate based on the total weight of the aerosolgenerating element. More preferably, the aerosol-generating element comprises at least 3 percent by weight of alginate based on the total weight of the aerosol-generating element.

An aerosol-generating element in accordance with the present invention may comprise up to 12 percent by weight of alginate based on the total weight of the aerosol-generating element. Preferably, the aerosol-generating element comprises less than or equal to 10 percent by weight of alginate based on the total weight of the aerosol-generating element. More preferably, the aerosol-generating element comprises less than or equal to 5 percent by weight of alginate based on the total weight of the aerosol-generating element.

In some embodiments, the aerosol-generating element comprises from 1 percent by weight to 12 percent by weight, preferably from 2 percent by weight to 12 percent by weight, more preferably from 3 percent by weight to 12 percent by weight of alginate based on the total weight of the aerosol-generating element.

In other embodiments, the aerosol-generating element comprises from 1 percent by weight to 10 percent by weight, preferably from 2 percent by weight to 10 percent by weight, more preferably from 3 percent by weight to 10 percent by weight of alginate based on the total weight of the aerosol-generating element.

In further embodiments, the aerosol-generating element comprises from 1 percent by weight to 5 percent by weight, preferably from 2 percent by weight to 5 percent by weight, more preferably from 3 percent by weight to 5 percent by weight of alginate based on the total weight of the aerosol-generating element.

In some embodiments, in an aerosol-generating element in accordance with the present invention the aerosol-generating formulation dispersed within the solid continuous matrix structure comprises at least one alkaloid.

As used herein with reference to the invention, the term “alkaloid compound” is used to describe any one of a class of naturally occurring organic compounds that contain one or more basic nitrogen atoms. Generally, an alkaloid contains at least one nitrogen atom in an amine-type structure. This or another nitrogen atom in the molecule of the alkaloid compound can be active as a base in acid-base reactions. Most alkaloid compounds have one or more of their nitrogen atoms as part of a cyclic system, such as for example a heterocylic ring. In nature, alkaloid compounds are found primarily in plants, and are especially common in certain families of flowering plants. However, some alkaloid compounds are found in animal species and fungi. In the context of the present invention, the term “alkaloid compounds” is used to describe both naturally derived alkaloid compounds and synthetically manufactured alkaloid compounds. Suitable alkaloid compounds for use in an aerosol-generating element in accordance with the invention include, but are not limited to, nicotine and anatabine. In preferred embodiments, the aerosol-generating formulation trapped within the solid continuous matrix structure comprises nicotine or anatabine.

In particularly preferred embodiments, the aerosol-generating formulation trapped within the solid continuous matrix structure comprises nicotine.

As used herein with reference to the invention, the term “nicotine” is used to describe nicotine, a nicotine base or a nicotine salt. In embodiments in which the aerosol-generating element comprises a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

The aerosol-generating element may comprise natural nicotine or synthetic nicotine.

The aerosol-generating element may comprise one or more monoprotic nicotine salts.

As used herein with reference to the invention, the term “monoprotic nicotine salt” is used to describe a nicotine salt of a monoprotic acid.

In general, the aerosol-generating element may comprise up to about 10 percent by weight of an alkaloid compound. In view of applications of the aerosol-generating element of the invention as a substrate in an aerosol-generating article, this is advantageous as the content of alkaloid compound may be increased and adjusted with a view to optimising the delivery of alkaloid compound in aerosol form to a consumer. Compared with existing aerosolgenerating substrates based on the use of plant material, this may advantageously allow for higher contents of alkaloid compound per volume of substrate (element or elements) or per weight of substrate (element or elements), which may be desirable from a manufacturing viewpoint.

Preferably, the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 10 percent by weight based on the total weight of the aerosol-generating element. More preferably, the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 8 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 5 percent by weight based on the total weight of the aerosol-generating element.

For example, the content of the at least one alkaloid in the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least 0.5 percent by weight of a total weight of the aerosol-generating element. Preferably, the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 1 percent by weight based on the total weight of the aerosol-generating element. In some embodiments, the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for from 1 percent by weight to 10 percent by weight, preferably from 1 percent by weight to 8 percent by weight, even more preferably from 1 percent by weight to 5 percent by weight based on the total weight of the aerosol-generating element.

Preferably, the aerosol-generating element comprises at least about 0.5 milligrams of nicotine. More preferably, the aerosol-generating element comprises at least about 1 milligram of nicotine. Even more preferably, the aerosol-generating element comprises at least about 1.5 milligrams of nicotine. In particularly preferred embodiments, the aerosolgenerating element comprises at least about 2 milligrams of nicotine, and most preferably at least about 2.5 milligrams of nicotine.

The aerosol-generating element may comprise up to about 6 milligrams of nicotine. Preferably, the aerosol-generating element comprises less than or equal to about 5 milligrams of nicotine. More preferably, the aerosol-generating element comprises less than or equal to about 4.5 milligrams of nicotine. Even more preferably, the aerosol-generating element comprises less than or equal to about 4 milligrams of nicotine. In particularly preferred embodiments, the aerosol-generating element comprises less than or equal to about 3.5 milligrams of nicotine, and most preferably less than or equal to about 3 milligrams of nicotine.

An aerosol-generating element in accordance with the present invention may be a substantially tobacco-free aerosol-generating element.

As used herein with reference to the invention, the term “substantially tobacco-free aerosol-generating element” describes an aerosol-generating element having a content of tobacco plant material of less than 1 percent by weight. For example, the aerosol-generating element may have a content of tobacco plant material of less than about 0.75 percent by weight, less than about 0.5 percent by weight or less than about 0.25 percent by weight.

The aerosol-generating element may be a tobacco-free aerosol-generating element.

As used herein with reference to the invention, the term “tobacco-free aerosolgenerating element” describes an aerosol-generating element having a content of tobacco plant material of 0 percent by weight.

In some embodiments, the aerosol-generating formulation dispersed within the continuous solid matrix structure further comprises an acid. More preferably, the aerosolgenerating formulation dispersed within the continuous solid matrix structure comprises one or more organic acids. Even more preferably, the aerosol-generating formulation dispersed within the continuous solid matrix structure comprises one or more carboxylic acids.

Suitable carboxylic acids for use in the aerosol-generating formulation of aerosolgenerating elements in accordance with the present invention include, but are not limited to: 2-Ethylbutyric acid, acetic acid, adipic acid, benzoic acid, butyric acid, cinnamic acid, cycloheptane-carboxylic acid, fumaric acid, glycolic acid, hexanoic acid, lactic acid, levulinic acid, malic acid, myristic acid, octanoic acid, oxalic acid, propanoic acid, pyruvic acid, succinic acid, and undecanoic acid.

In particularly preferred embodiments, the acid is selected from the group consisting of lactic acid, levulinic acid, benzoic acid, citric acid, fumaric acid and combinations thereof. Most preferably, the acid is lactic acid.

The inclusion of an acid is especially preferred in embodiments of the aerosol-generating element wherein the aerosol-generating formulation dispersed within the continuous solid matrix structure comprises nicotine, as it has been observed that the presence of an acid may stabilise dissolved species in the aerosol-generating formulation, such as with nicotine and other plant extracts. Without wishing to be bound by theory, it is understood that the acid may interact with the nicotine molecule, such that protonated nicotine is stabilised. As protonated nicotine is non-volatile, it is more easily found in the liquid or particulate phase rather than in the vapour phase of an aerosol obtained by heating the aerosol-generating element. As such, loss of nicotine during manufacturing of the aerosol-generating element can be minimised, and higher, better controlled nicotine delivery to the consumer can advantageously be ensured.

The aerosol-generating element may comprise up to about 10 percent by weight of an acid.

Preferably, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for at least 0.5 percent by weight of a total weight of the aerosol-generating element. More preferably, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for at least 1 percent by weight of a total weight of the aerosol-generating element. Even more preferably, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for at least 2 percent by weight of a total weight of the aerosol-generating element.

Preferably, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for less than or equal to 8 percent by weight based on a total weight of the aerosol-generating element. More preferably, the acid content in the aerosolgenerating formulation dispersed within the solid porous substrate accounts for less than or equal to 5 percent by weight based on a total weight of the aerosol-generating element.

In some embodiments, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for from 0.5 percent by weight to 10 percent by weight, preferably from 1 percent by weight to 10 percent by weight, more preferably from 2 percent by weight to 10 percent by weight based on a total weight of the aerosol-generating element. In other embodiments, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for from 0.5 percent by weight to 8 percent by weight, preferably from 1 percent by weight to 8 percent by weight, more preferably from 2 percent by weight to 8 percent by weight based on a total weight of the aerosol-generating element.

In further embodiments, the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for from 0.5 percent by weight to 5 percent by weight, preferably from 1 percent by weight to 5 percent by weight, more preferably from 2 percent by weight to 5 percent by weight based on a total weight of the aerosol-generating element.

Where a multivalent acid, such as a multivalent carboxylic acid, is present in the aerosolgenerating formulation dispersed within the solid porous substrate in combination with nicotine, it may be preferable to provide a molar ratio of the acid groups to nicotine of between about 0.5:1 and about 2:1 , more preferably between about 0.75:1 and about 1.5:1 , most preferably about 1 :1. The use of a multivalent acid therefore enables a lower weight amount of the acid to be used whilst still providing the same level of protonation of the nicotine.

An aerosol-generating element according to the present invention preferably comprises less than or equal to about 25 percent by weight of water.

More preferably, the aerosol-generating element comprises less than or equal to about 20 percent by weight of water. Even more preferably, the aerosol-generating element comprises less than or equal to about 15 percent of water.

An aerosol-generating element according to the present invention preferably comprises at least about 2.5 percent by weight of water. More preferably, the aerosol-generating element according to the present invention preferably comprises at least about 5 percent by weight of water. Even more preferably, the aerosol-generating element according to the present invention preferably comprises at least about 7.5 percent by weight of water. Most preferably, the aerosol-generating element according to the present invention preferably comprises at least about 10 percent by weight of water.

In general, it has been observed that the presence of some water contributes to imparting desirable stability to the aerosol-generating element. At the same time, a residual content of water of 25 percent by weight or less is desirable as an aerosol-generating element may be obtained that is substantially not sticky. Further, when heating an aerosol-generating element with a lower water content, an aerosol more concentrated in the polyhydric alcohol and in the alkaloid or cannabinoid compound, such as nicotine, may be provided to the consumer.

In some embodiments, the aerosol-generating element according to the present invention comprises from about 2.5 percent by weight to about 25 percent by weight of water. Preferably, the aerosol-generating element according to the present invention comprises from about 5 percent by weight to about 25 percent by weight of water. More preferably, the aerosol-generating element according to the present invention comprises from about 7.5 percent by weight to about 25 percent by weight of water. Most preferably, the aerosolgenerating element according to the present invention comprises from about 10 percent by weight to about 25 percent by weight of water.

In other embodiments, the aerosol-generating element according to the present invention comprises from about 2.5 percent by weight to about 20 percent by weight of water. Preferably, the aerosol-generating element according to the present invention comprises from about 5 percent by weight to about 20 percent by weight of water. More preferably, the aerosol-generating element according to the present invention comprises from about 7.5 percent by weight to about 20 percent by weight of water. Most preferably, the aerosolgenerating element according to the present invention comprises from about 10 percent by weight to about 20 percent by weight of water.

In further embodiments, the aerosol-generating element according to the present invention comprises from about 2.5 percent by weight to about 15 percent by weight of water. Preferably, the aerosol-generating element according to the present invention comprises from about 5 percent by weight to about 15 percent by weight of water. More preferably, the aerosol-generating element according to the present invention comprises from about 7.5 percent by weight to about 15 percent by weight of water. Most preferably, the aerosolgenerating element according to the present invention comprises from about 10 percent by weight to about 15 percent by weight of water.

In yet further embodiments, the aerosol-generating element according to the present invention comprises from about 2.5 percent by weight to about 10 percent by weight of water. Preferably, the aerosol-generating element according to the present invention comprises from about 5 percent by weight to about 10 percent by weight of water. More preferably, the aerosol-generating element according to the present invention comprises from about 7.5 percent by weight to about 10 percent by weight of water. Most preferably, the aerosolgenerating element according to the present invention comprises from about 10 percent by weight to about 10 percent by weight of water.

An aerosol-generating element according to the present invention preferably has a water activity of less than or equal to about 0.7.

The term “water activity” is used herein with reference to the present invention to denote the ratio of the partial water vapour pressure in equilibrium with an aerosol-generating element to the water-vapour saturation pressure in equilibrium with pure water at the same temperature. As such, water activity is a dimensionless quantity between 0, which corresponds to a completely anhydrous substance, and 1 , which corresponds to pure salt-free water. Methods of measuring the water activity of an aerosol-generating element in accordance with the present invention are described in the 2017 publication of ISO 18787 (Foodstuffs - Determination of water activity).

An aerosol-generating element in accordance with the present invention may optionally further comprise a flavourant. The flavourant may be in liquid form, or solid form. Optionally, the flavourant may be provided in a microencapsulated form wherein the flavourant is released upon heating.

Preferably, the aerosol-generating element comprises at least about 0.05 percent by weight of flavourant, more preferably at least about 0.1 percent by weight of flavourant based on the total weight of the aerosol-generating element. The aerosol-generating element preferably comprises less than or equal to about 1 percent by weight of flavourant, more preferably less than or equal to about 0.5 percent by weight of flavourant based on the total weight of the aerosol-generating element.

In some embodiments, the aerosol-generating element comprises from about 0.05 percent by weight to about 1 percent by weight of flavourant, preferably from about 0.05 percent by weight to about 0.5 percent by weight of flavourant based on the total weight of the aerosol-generating element. In other embodiments, the aerosol-generating element comprises from about 0.1 percent by weight to about 1 percent by weight of flavourant, preferably from about 0.1 percent by weight to about 0.5 percent by weight of flavourant based on the total weight of the aerosol-generating element.

Suitable flavourants for use in an aerosol-generating element in accordance with the present invention include, but are not limited to: menthol, mint such as peppermint or spearmint, cocoa, liquorice, fruit (such as citrus), gamma octalactone, vanillin, spices (such as cinnamon), methyl salicylate, linalool, eugenol, eucalyptol, bergamot oil, eugenol oil, geranium oil, lemon oil, ginger oil, and tobacco flavour.

As described above, to manufacture the aerosol-generating element, a portion of the aerosol-generating solution may be added to a cross-linking solution of multivalent cations to cross-link the one or more matrix-forming polymers, thereby forming an aerosol-generating element having a continuous polymer matrix structure and the aerosol-generating formulation comprising aerosol-generating components dispersed within the continuous polymer matrix.

In some embodiments, the aerosol-generating element further comprises at least 0.05 percent by weight of a cross-linking agent.

Preferably, the cross-linking agent comprises a cross-linking solution of multivalent cations.

Preferred multivalent cations include calcium, iron, aluminium, manganese, copper, zinc or lanthanum. A particularly preferred salt is calcium chloride. In certain preferred embodiments of the invention in which the aerosol-generating solution comprises an acid, as discussed above, the calcium salt provided in the cross-linking solution may advantageously be a salt of the same acid. For example, in embodiments in which the aerosol-generating solution comprises lactic acid, the cross-linking solution may advantageously comprise calcium lactate.

Where the aerosol-generating solution comprises nicotine, the acid in the aerosolgenerating solution forms a nicotine salt with the nicotine. The use of a calcium salt corresponding to the acid in the aerosol-generating solution therefore provides the same salt in the cross-linking solution as in the aerosol-generating solution. This, in turn, advantageously limits the diffusion of nicotine salts out of the aerosol-generating solution into the cross-linking solution during the cross-linking step. A higher concentration of the nicotine salt can therefore be retained within the aerosol-generating element. Furthermore, any potential waste of the nicotine and acid during the production of the aerosol-generating element can be reduced.

An aerosol-generating element in accordance with the invention may have an equivalent diameter of at least 0.5 millimetres.

The term “equivalent diameter of an aerosol-generating element” is used herein to denote the diameter of the sphere which has the same volume as the aerosol-generating element. In general, the aerosol-generating element may have any shape, although a spherical or quasi-spherical shape, such as an egg shape or ellipsoid shape is preferred. For an aerosol-generating element having a spherical shape and a circular transverse crosssection, the equivalent diameter is the diameter of the cross-section of the aerosol-generating element.

Preferably, the aerosol-generating element has an equivalent diameter of at least 1 millimetre. More preferably, the aerosol-generating element has an equivalent diameter of at least 1.5 millimetres. Even more preferably, the aerosol-generating element has an equivalent diameter of at least 2 millimetres.

An aerosol-generating element in accordance with the invention preferably has an equivalent diameter of less than or equal to 10 millimetres. More preferably, the aerosolgenerating element has an equivalent diameter of less than or equal to 7 millimetres. Even more preferably, the aerosol-generating element has an equivalent diameter of less than or equal to 4 millimetres.

In some embodiments, the aerosol-generating element has an equivalent diameter from 0.5 millimetres to 10 millimetres, preferably from 1 millimetre to 10 millimetres, more preferably from 1.5 millimetres to 10 millimetres, even more preferably from 2 millimetres to 10 millimetres. In other embodiments, the aerosol-generating element has an equivalent diameter from 0.5 millimetres to 7 millimetres, preferably from 1 millimetre to 7 millimetres, more preferably from 1.5 millimetres to 7 millimetres, even more preferably from 2 millimetres to 7 millimetres. In further embodiments, the aerosol-generating element has an equivalent diameter from 0.5 millimetres to 4 millimetres, preferably from 1 millimetre to 4 millimetres, more preferably from 1.5 millimetres to 4 millimetres, even more preferably from 2 millimetres to 4 millimetres.

In some embodiments, a plurality of aerosol-generating elements in accordance with the present invention are provided that have an equivalent diameter in the range from 1 millimetre to 3 millimetres or from 1 millimetre to 2 millimetres, such as for example 1.5 millimetres. Aerosol-generating elements having an equivalent diameter falling within these ranges may for example be incorporated into an aerosol-generating article for use with an aerosolgenerating device comprising a heater element for heating the aerosol-generating elements.

In other embodiments, a plurality of aerosol-generating elements in accordance with the present invention are provided that have an equivalent diameter in the range from 3 millimetres to 5 millimetres or from 3 millimetre to 4 millimetres. Aerosol-generating elements having an equivalent diameter falling within these ranges may for example be provided in a container (for example, a bag), each individual aerosol-generating element being available for use. Alternatively, aerosol-generating elements having an equivalent diameter falling within these ranges may for example be provided in a rod-shaped aerosol-generating article, each individual aerosol-generating element being available for use.

Aerosol-generating elements in accordance with the present invention may have an ovality up to about 35 percent.

The term “ovality” as used herein with reference to the present invention denotes the degree of deviation from a perfect circle. Ovality is expressed as a percentage and the mathematical definition is given below.

To determine the ovality of an object, such as an aerosol-generating element, the object can be viewed along a direction substantially perpendicular to a cross-section of the aerosolgenerating element. By way of example, the aerosol-generating element can be positioned on a transparent stage so that an image of the aerosol-generating element is recorded by a suitable imaging device located below the stage. Dimension “a” is taken to be the largest external diameter of the image of the aerosol-generating element, and dimension “b” is taken to be the smallest external diameter of the image of the aerosol-generating element. The process is repeated for a total of ten aerosol-generating elements having the same composition and prepared by means of the same process and under the same operating conditions. The number average of the ten ovality measurements is recorded as the ovality for that aerosol-generating element.

Preferably, an aerosol-generating element in accordance with the invention has an ovality of less than or equal to about 30 percent. More preferably, an aerosol-generating element in accordance with the invention has an ovality of less than or equal to about 25 percent. Even more preferably, an aerosol-generating element in accordance with the invention has an ovality of less than or equal to about 20 percent.

An aerosol-generating element in accordance with the invention typically has an ovality of at least about 1 percent. Preferably, the aerosol-generating element has an ovality of at least 2 percent. More preferably, the aerosol-generating element has an ovality of at least 3 percent. Even more preferably, the aerosol-generating element has an ovality of at least 4 percent.

In some embodiments, the aerosol-generating element has an ovality from about 1 percent to about 30 percent, more preferably from about 2 percent to about 30 percent, more preferably from about 3 percent to about 30 percent, even more preferably from about 4 percent to about 30 percent.

In other embodiments, the aerosol-generating element has an ovality from about 1 percent to about 25 percent, more preferably from about 2 percent to about 25 percent, more preferably from about 3 percent to about 25 percent, even more preferably from about 4 percent to about 25 percent.

In further embodiments, the aerosol-generating element has an ovality from about 1 percent to about 20 percent, more preferably from about 2 percent to about 30 percent, more preferably from about 3 percent to about 20 percent, even more preferably from about 4 percent to about 20 percent.

An aerosol-generating article in accordance with the present invention may have an exposed surface area to volume ratio up to 25 cm^-1.

The expression “exposed surface area to volume ratio” as used herein with reference to the present invention denotes the ratio between the overall outer surface area of the aerosolgenerating element, that is exposed and available for heat and mass exchange, and the overall volume of the aerosol-generating element.

As the aerosol-generating elements in accordance with the invention have low ovality and may be assimilated to spherical objects, the volume of an aerosol-generating element in accordance with the invention can be expressed by the formula

The exposed surface area of an aerosol-generating element in accordance with the invention can be estimated by the formula

Dimension R_eq denotes an equivalent radius of the aerosol-generating element.

Preferably, the aerosol-generating article has an exposed surface area to volume ratio of at least about 0.083 cm^-1. More preferably, the aerosol-generating article has an exposed surface area to volume ratio of at least about 0.166 cm^-1. Even more preferably, the aerosolgenerating article has an exposed surface area to volume ratio of at least about 0.249 cm^-1.

The aerosol-generating article preferably has an exposed surface area to volume ratio of less than or equal to about 24 cm^-1. More preferably, the aerosol-generating article has an exposed surface area to volume ratio of less than or equal to about 20 cm^-1. Even more preferably, the aerosol-generating article has an exposed surface area to volume ratio of less than or equal to about 16 cm^-1. In some embodiment, the aerosol-generating article has an exposed surface area to volume ratio from about 0.083 cm^-1 to about 24 cm^-1, more preferably from about 0.166 cm^-1 to about 24 cm^-1, even more preferably from about 0.249 cm^-1 to about 24 cm^-1.

In other embodiments, the aerosol-generating article has an exposed surface area to volume ratio from about 0.083 cm^-1 to about 20 cm^-1, more preferably from about 0.166 cm^-1 to about 20 cm^-1, even more preferably from about 0.249 cm^-1 to about 20 cm^-1.

In further embodiments, the aerosol-generating article has an exposed surface area to volume ratio from about 0.083 cm^-1 to about 16 cm^-1, more preferably from about 0.166 cm^-1 to about 16 cm^-1, even more preferably from about 0.249 cm^-1 to about 16 cm^-1.

In some embodiments, aerosol-generating elements in accordance with the present invention may be coated. In practice, an outer coating layer may optionally be provided on the aerosol-generating elements as described above. This may be achieved by means of a coating step that may take place before the drying step or after the drying step. An optional drying step may be incorporated after the coating step.

The provision of a coating layer on the aerosol-generating element may be desirable for many different reasons. For example, a coating layer may advantageously limit the permeation of oxygen or water vapour into the aerosol-generating element, which may help to extend the shelf life of the aerosol-generating element. Alternatively or in addition, a coating layer may help to protect the structural integrity of the aerosol-generating element, or to provide improved smoothness of the aerosol-generating element. In certain embodiments, a relatively brittle coating layer may be added to the aerosol-generating element that is adapted to be broken by the consumer prior to use. This type of coating layer can therefore provide the consumer with a tactile and audible indication that the aerosol-generating element has been activated. Alternatively or in addition, the provision of a coating layer on the aerosolgenerating element may be used to adjust the colour of the aerosol-generating element, for example, to provide a visual indication of a property of the aerosol-generating element, such as the flavour or the content of nicotine.

Suitable types of coating material would be known to the skilled person. For example, a coating layer of a water soluble film former, such as HPMC or shellac, may be applied to the aerosol-generating element. Such film formers will adhere strongly to the surface of the aerosol-generating element. In a further example, a coating layer of sodium alginate may be added, which will cross-link with any remaining calcium ions on the surface of the aerosolgenerating element to form a thin film of calcium alginate.

A coating layer may be applied to the outer surface of the aerosol-generating element using a variety of coating techniques. Suitable apparatus and techniques would be known to the skilled person. In some embodiments, aerosol-generating elements according to the present invention comprise: from 2 to 10 percent by weight of alginate based on the total weight of the aerosolgenerating element; from 4 to 25 percent by weight of water based on the total weight of the aerosolgenerating element; from 40 to 75 percent by weight of glycerin based on the total weight of the aerosolgenerating element; from 5 percent to 25 percent by weight of activated carbon; from 0.05 to 1 percent by weight of calcium ions; optionally up to 8 percent by weight of nicotine based on the total weight of the aerosolgenerating element; optionally up to 5 percent by weight of an acid based on the total weight of the aerosolgenerating element.

In some preferred embodiments, aerosol-generating elements according to the present invention comprise: from 3 to 5 percent by weight of alginate based on the total weight of the aerosolgenerating element; from 15 to 22 percent by weight of water based on the total weight of the aerosolgenerating element; from 40 to 75 percent by weight of glycerin based on the total weight of the aerosolgenerating element; from 5 percent to 25 percent by weight of activated carbon; from 0.05 to 1 percent by weight of calcium ions; optionally up to 8 percent by weight of nicotine based on the total weight of the aerosolgenerating element; optionally up to 5 percent by weight of an acid based on the total weight of the aerosolgenerating element.

Aerosol-generating elements in accordance with the present disclosure may be incorporated into an aerosol-generating article for producing an inhalable aerosol upon heating.

Because aerosol-generating elements in accordance with the invention are easy to manufacture and predetermined, discrete amounts of an aerosol-generating formulation may thus be provided in encapsulated form, and because the composition of the aerosolgenerating formulation - especially as regards the content of polyhydric alcohol and of the alkaloid or cannabinoid compound - can be finely tuned and controlled, aerosol-generating elements in accordance with the invention are versatile and can be used as substrates in a number of arrangements.

In an embodiment, an aerosol-generating article for producing an inhalable aerosol upon heating comprises an aerosol-generating element as described above and a downstream section downstream of the aerosol-generating element, the downstream section comprising an aerosol-cooling element comprising a hollow tubular element and a mouthpiece element downstream of the aerosol-cooling element.

By way of example, a plurality of aerosol-generating elements in accordance with the invention may be provided within a cavity defined by a tubular element, such that the outer surface of the aerosol-generating elements is exposed inside the longitudinal airflow channel defined by the cavity. Upon heating, an aerosol can be generated from the aerosol-generating elements, which is thus released into the airflow channel and can be drawn through the tubular element into the consumer’s mouth.

Such an aerosol-generating article may find use as part of an aerosol-generating system, wherein it is paired with an aerosol-generating device comprising a heating arrangement.

An aerosol-generating element in accordance with the present disclosure may be incorporated into a cartridge for an aerosol-generating system.

In an embodiment, such a cartridge comprises an aerosol-generating element as described above and a heating arrangement, the heating arrangement comprising: an electrical heating element arranged to heat at least a portion of the aerosol-generating element to generate an aerosol, and at least one cartridge electrical contact arranged to engage with corresponding at least one device electrical contact of an aerosol-generating device.

For example, an aerosol-generating system for producing an inhalable aerosol comprises a cartridge as described above and an aerosol-generating device, the aerosolgenerating device comprising a power supply and at least one device electrical contact.

An aerosol-generating element in accordance with the present invention may optionally further comprise a plurality of susceptor particles. Susceptor particles are conductive particles that have the ability to convert electromagnetic energy and convert it to heat. When located in an alternating electromagnetic field, eddy currents are induced and hysteresis losses occur in the susceptor particles causing heating of the susceptor. As the susceptor particles are located in thermal contact or close thermal proximity with the aerosol-generating formulation of the aerosol-generating element, the aerosol-generating formulation is heated by the susceptor particles such that an aerosol is formed.

The inclusion of susceptor particles in the aerosol-generating solution therefore provides an aerosol-generating element that is inductively heatable. When the aerosol-generating element is used in a device comprising an induction heater, changing electromagnetic fields generated by one or several induction coils of an inductive heating device heats the susceptor particles, which then transfer the heat to the surrounding aerosol-generating formulation of the aerosol-generating element, mainly by conduction of heat.

The susceptor particles may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-generating formulation. Preferred susceptor particles may comprise or consist of a ferromagnetic material, for example a ferromagnetic alloy, ferritic iron, or a ferromagnetic steel or stainless steel. Suitable susceptor particles may be, or comprise, aluminium. Preferred susceptor particles may be heated to a temperature in excess of 250 degrees Celsius. Suitable susceptor particles may comprise a non-metallic core with a metal layer disposed on the non-metallic core, for example metallic tracks formed on a surface of a ceramic core. Susceptor particles may have a protective external layer, for example a protective ceramic layer or protective glass layer encapsulating the susceptor particle. The susceptor particles may comprise a protective coating formed by a glass, a ceramic, or an inert metal, formed over a core of susceptor material.

The susceptor particles may have an average particle size up to about 60 micrometres. For example, the susceptor particles may have an average particle size of less than or equal to about 50 micrometres, or less than or equal to about 40 micrometres or less than or equal to about 35 micrometres. Typically, in an aerosol-generating element in accordance with the present invention the susceptor particles have an average particle size of at least about 1 micrometre, or at least about 2 micrometres, or at least about 5 micrometres or at least about 10 micrometres. For example, the susceptor particles in the aerosol-generating element may have an average particle size from about 1 micrometre to about 60 micrometres, or from about 2 millimetres to about 50 micrometres, or from about 5 micrometres to about 40 micrometres, or from about 10 micrometres to about 35 micrometres.

For example, the aerosol-generating element may comprise at least 1 percent by weight and up to 15 percent by weight of susceptor particles based on the total weight of the aerosolgenerating element.

The invention is defined in the claims. However, below there is provided a non- exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Examples

Example Ex1 : An aerosol-generating element for use in an aerosol-generating article or system, the aerosol-generating element comprising: a solid continuous matrix structure; a solid porous substrate dispersed within the solid continuous matrix structure, the solid porous substrate comprising activated carbon; an aerosol-generating formulation also dispersed within the solid continuous matrix structure, wherein the aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element, a portion of the aerosolgenerating formulation being sorbed in the solid porous substrate, wherein the solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers.

Example Ex2: An aerosol-generating element according to example Ex 1 wherein the aerosol-generating formulation dispersed within the solid continuous matrix structure comprises a polyhydric alcohol.

Example Ex3: An aerosol-generating element according to example Ex 2 wherein a polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounting for at least 40 percent by weight based on the total weight of the aerosol-generating element.

Example Ex4: An aerosol-generating element according to any one of examples Ex1 to Ex3 wherein the activated carbon content accounts for at least 5 percent by weight based on the total weight of the aerosol-generating element.

Example Ex5: An aerosol-generating element according to any one of examples Ex1 to Ex4, wherein the solid porous substrate has a standard BET surface area of between 100 metres squared per gram and 600 metres squared per gram.

Example Ex6: An aerosol-generating element according to any one of examples Ex1 to Ex5, wherein the solid porous substrate has a pore volume measured using adsorption isotherms of either carbon dioxide (VDR (CO2)) or nitrogen (VDR (N2)) of at least 0.05 cubic centimetres per gram.

Example Ex7: An aerosol-generating element according to any one of examples Ex1 to Ex6, wherein the solid porous substrate has a pore volume measured using adsorption isotherms of either carbon dioxide (VDR (CO2)) or nitrogen (VDR (N2)) of no more than 0.35 cubic centimetres per gram.

Example Ex8: An aerosol-generating element according to any one of examples Ex1 to Ex7, wherein the solid porous substrate has a pore volume measured using V_meso (N2) of at least 0.01 cubic centimetres per gram.

Example Ex9: An aerosol-generating element according to any one of examples Ex1 to Ex8, wherein the solid porous substrate has a pore volume measured using V_meso (N2) of no more than 0.15 cubic centimetres per gram.

Example Ex10: An aerosol-generating element according to any one of examples Ex1 to Ex9, wherein the solid porous substrate has a pore volume measured using V_meso (Hg) of at least 0.001 cubic centimetres per gram. Example Ex11 : An aerosol-generating element according to any one of examples Ex1 to Ex10, wherein the solid porous substrate has a pore volume measured using V_meso (Hg) of no more than 0.1 cubic centimetres per gram.

Example Ex12: An aerosol-generating element according to any one of examples Ex1 to Ex11 , wherein the solid porous substrate has a total mesopore volume (VT_meso) of at least 0.01 cubic centimetres per gram.

Example Ex13: An aerosol-generating element according to any one of examples Ex1 to Ex12, wherein the solid porous substrate has a total mesopore volume (VT_meso) of no more than 1 cubic centimetre per gram.

Example Ex14: An aerosol-generating element according to any one of examples Ex1 to Ex13, wherein the solid porous substrate has a surface concentration of oxygen (Ototai) of at least 3 percent when measured using temperature-programmed desorption (TPD).

Example Ex15: An aerosol-generating element according to any one of examples Ex1 to Ex14, wherein the solid porous substrate has a surface concentration of oxygen (Ototai) of no more than 20 percent when measured using temperature-programmed desorption (TPD).

Example Ex16: An aerosol-generating element according to any one of examples Ex1 to Ex15, wherein the activated carbon content accounts for at least 10 percent by weight based on the total weight of the aerosol-generating element.

Example Ex17: An aerosol-generating element according to any one of examples Ex1 to Ex16, wherein the activated carbon content accounts for less than or equal to 25 percent by weight based on the total weight of the aerosol-generating element.

Example Ex18: An aerosol-generating element according to any one of examples Ex1 to Ex17, wherein the activated carbon content accounts for less than or equal to 20 percent by weight based on the total weight of the aerosol-generating element.

Example Ex19: An aerosol-generating element according to any one of examples Ex2 to Ex18, wherein the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 50 percent by weight based on the total weight of the aerosol-generating element.

Example Ex20: An aerosol-generating element according to any one of examples Ex2 to Ex19, wherein the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 75 percent by weight based on the total weight of the aerosol-generating element.

Example Ex21 : An aerosol-generating element according to any one of examples Ex2 to Ex20, wherein the polyhydric alcohol content in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 65 percent by weight based on the total weight of the aerosol-generating element. Example 22: An aerosol-generating element according to any one of examples Ex2 to Ex21 , wherein the polyhydric alcohol is glycerin, propylene glycol, or a combination of glycerin and propylene glycol.

Example 23: An aerosol-generating element according to any one of examples Ex1 to Ex22, wherein the one or more matrix-forming polymers include at least one of alginate and pectin.

Example 24: An aerosol-generating element according to example Ex23, wherein the solid continuous matrix structure is an alginate matrix.

Example Ex25: An aerosol-generating element according to any one of examples Ex1 to Ex24, wherein the aerosol-generating element comprises at least 2 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element.

Example Ex26: An aerosol-generating element according to any one of examples Ex1 to Ex25, wherein the aerosol-generating element comprises at least 3 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosol-generating element.

Example Ex27: An aerosol-generating element according to any one of examples Ex1 to Ex26, wherein the aerosol-generating element comprises less than or equal to 10 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosolgenerating element.

Example Ex28: An aerosol-generating element according to any one of examples Ex1 to Ex27, wherein the aerosol-generating element comprises less than or equal to 5 percent by weight of the one or more matrix-forming polymers based on the total weight of the aerosolgenerating element.

Example Ex29: An aerosol-generating element according to any one of examples Ex1 to Ex28, wherein the aerosol-generating formulation trapped within the solid continuous matrix structure further comprises nicotine or anatabine.

Example Ex30: An aerosol-generating element according to example Ex29, wherein the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 8 percent by weight based on the total weight of the aerosol-generating element.

Example 31 : An aerosol-generating element according to examples Ex29 or Ex30, wherein the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for less than or equal to 5 percent by weight based on the total weight of the aerosol-generating element.

Example 32: An aerosol-generating element according to any one of examples Ex29 to Ex31 wherein the content of nicotine or anatabine in the aerosol-generating formulation trapped within the solid continuous matrix structure accounts for at least 1 percent by weight based on the total weight of the aerosol-generating element.

Example Ex33: An aerosol-generating element according to any one of examples Ex1 to Ex32, wherein the aerosol-generating formulation trapped within the solid continuous matrix structure further comprises an acid.

Example Ex34: An aerosol-generating element according to example Ex33, wherein the acid is selected from the group consisting of lactic acid, levulinic acid, benzoic acid, citric acid, fumaric acid and combinations thereof.

Example Ex35: An aerosol-generating element according to example Ex33 or Ex34, wherein the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for at least 0.5 percent by weight of a total weight of the aerosolgenerating element.

Example Ex36: An aerosol-generating element according to example Ex33, Ex34 or Ex35, wherein the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for at least 1 percent by weight based on a total weight of the aerosol-generating element.

Example Ex37: An aerosol-generating element according to any one of examples Ex 33 to Ex36, wherein the acid content in the aerosol-generating formulation dispersed within the solid porous substrate accounts for less than or equal to 5 percent by weight based on a total weight of the aerosol-generating element.

Example Ex38: An aerosol-generating element according to any one of examples Ex1 to Ex37 further comprising less than or equal to 25 percent by weight of water based on a total weight of the aerosol-generating element.

Example Ex39: An aerosol-generating element according to any one of examples Ex1 to Ex38 further comprising less than or equal to 22 percent by weight of water based on a total weight of the aerosol-generating element.

Example Ex40: An aerosol-generating element according to any one of examples Ex1 to Ex39 further comprising at least 4 percent by weight of water based on a total weight of the aerosol-generating element.

Example Ex41 : An aerosol-generating element according to any one of examples Ex1 to Ex40 further comprising at least 10 percent by weight of water based on a total weight of the aerosol-generating element.

Example Ex42: An aerosol-generating element according to any one of examples Ex1 to Ex41 further comprising at least 15 percent by weight of water based on a total weight of the aerosol-generating element.

Example Ex43: An aerosol-generating element according to any one of examples Ex1 to Ex42 further comprising at least 0.05 percent by weight of a cross-linking agent. Example Ex44: An aerosol-generating element according to example Ex43, wherein the cross-linking agent comprises a cross-linking solution of multivalent cations.

Example Ex45: An aerosol-generating element according to any one of the examples Ex1 to Ex44 having an equivalent diameter of at least 0.5 millimetres.

Example Ex46: An aerosol-generating element according to any one of examples Ex1 to Ex45 having an equivalent diameter of at least 1 millimetre.

Example Ex47: An aerosol-generating element according to any one of examples Ex1 to Ex46 having an equivalent diameter of at least 1.5 millimetres.

Example Ex48: An aerosol-generating element according to any one of examples Ex1 to Ex47 having an equivalent diameter of less than or equal to 10 millimetres.

Example Ex49: An aerosol-generating element according to any one of examples Ex1 to Ex48 having an equivalent diameter of less than or equal to 7 millimetres.

Example Ex50: An aerosol-generating element according to any one of examples Ex1 to Ex49 having an equivalent diameter of less than or equal to 4 millimetres.

Example Ex51 : An aerosol-generating element according to any one of examples Ex1 to Ex50 having an ovality from about 2 percent to about 30 percent.

Example Ex52: An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising: an aerosol-generating element according to any of examples Ex1 to Ex 51 .

Example Ex53: An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising an internal cavity and an aerosol-generating element according to any of examples Ex1 to Ex 51 located within the internal cavity.

Example Ex54: An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising an internal cavity and a plurality of aerosolgenerating elements according to any of examples Ex1 to Ex 51 located within the internal cavity.

Example Ex55: An aerosol-generating article according to example Ex54, wherein a thickness of the aerosol-generating article is preferably less than 50 percent of both a length and a width of the aerosol-generating article.

Example Ex56: An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising: an aerosol-generating element according to any of examples Ex1 to Ex 51 , and a downstream section downstream of the aerosolgenerating element, the downstream section comprising an aerosol-cooling element comprising a hollow tubular element and a mouthpiece element downstream of the aerosolcooling element. Example Ex57: An aerosol-generating system for producing an inhalable aerosol, the system comprising: aerosol-generating article according to example Ex55, and an aerosolgenerating device comprising a heating arrangement.

Example Ex58: A cartridge for an aerosol-generating system, the cartridge comprising: an aerosol-generating element according to any of examples Ex1 to Ex51 ; a heating arrangement comprising: an electrical heating element arranged to heat at least a portion of the aerosol-generating element to generate an aerosol, and at least one cartridge electrical contact arranged to engage with corresponding at least one device electrical contact of an aerosol-generating device.

Example Ex59. An aerosol-generating system for producing an inhalable aerosol, the system comprising: a cartridge according to example Ex58, and an aerosol-generating device, the aerosol-generating device comprising a power supply and at least one device electrical contact.

Examples will now be further described with reference to the figures in which:

Figure 1 shows a schematic side view of an aerosol-generating element according to the present invention;

Figure 2 shows a cross sectional view of an aerosol-generating article according to the present invention;

Figure 3 shows a cross sectional view of a first aerosol-generating system according to the present invention;

Figure 4 shows a schematic perspective view of a second aerosol-generating article comprising a plurality of aerosol-generating elements of the type shown in Figure 1 ; and

Figure 5 shows an exploded perspective view of the aerosol-generating article of Figure 4.

An aerosol-generating element 10 in accordance with the present invention is illustrated schematically in Figure 1. The aerosol-generating element 10 is substantially spherical and has an equivalent diameter DEQ from 1 millimetre to 2 millimetres, for example 1.5 millimetres.

Further details about how the aerosol-generating element 10 is formed are provided below (see Example A).

The aerosol-generating article 100 shown in Figure 2 extends from an upstream end 101 to a downstream end 102. The aerosol-generating article 100 comprises an aerosolgenerating substrate reservoir 103 at the upstream end 101 of the aerosol-generating article 100. The aerosol-generating substrate reservoir 103 comprises a plurality of aerosolgenerating elements 10 disposed within a cavity 104 and delimited at the upstream and downstream ends by respective porous elements 105 and 106.

The aerosol-generating article 100 further comprises a downstream section located immediately downstream of the aerosol-generating substrate reservoir 103. The downstream section comprises a hollow tubular element 107 and a mouthpiece element 108 downstream of the hollow tubular element 107.

The hollow tubular element 107 defines a hollow section of the aerosol-generating article 100. The hollow tubular element 107 does not substantially contribute to the overall RTD of the aerosol-generating article 100. In more detail, an RTD of the hollow tubular element 107 is about 0 mm H2O.

The hollow tubular element 107 is provided in the form of a hollow cylindrical tube made of cardboard. The hollow tubular element 107 defines an internal cavity 109 that extends all the way from an upstream end of the hollow tubular element 107 to a downstream end of the hollow tubular element 107. The internal cavity 109 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 109.

The aerosol-generating article 100 comprises a ventilation zone 110 provided at a location along the hollow tubular element 107. The ventilation zone 110 comprises a circumferential row of openings or perforations circumscribing the hollow tubular element 107. The perforations of the ventilation zone 110 extend through the wall of the hollow tubular element 107, in order to allow fluid ingress into the internal cavity 109 from the exterior of the article 100. A ventilation level of the aerosol-generating article 100 is about 40 percent.

The mouthpiece element 108 extends from the downstream end of the hollow tubular element 107 to the downstream end 102 of the aerosol-generating article 100. The mouthpiece element 108 comprises a low-density filter segment.

The aerosol-generating article 100 comprises a wrapper 111 circumscribing the aerosol-generating substrate reservoir 103, the hollow tubular element 107, and the mouthpiece element 108. The ventilation zone 110 may also comprise a circumferential row of perforations provided through the wrapper 111.

The aerosol-generating article 100 has an overall length of about 45 millimetres and an external diameter of about 7.2 millimetres.

Figure 3 illustrates a first aerosol-generating system 200 according to the present invention. The first aerosol-generating system 200 comprises the aerosol-generating article 100 of Figure 2, and a first aerosol-generating device 250. The aerosol-generating device 250 comprises a housing (or body) 201 , extending between a downstream end and an upstream end. The housing 201 defines a heating chamber 202 for receiving an aerosol-generating article 100. The heating chamber 202 is defined by a closed, upstream end and an open, downstream end. The downstream end of the heating chamber 202 is located at the downstream end of the aerosol-generating device 250. The aerosol-generating article 100 is configured to be received through the open, downstream end of the heating chamber 202 and is configured to abut a closed, upstream end of the heating chamber 202, when the aerosolgenerating article 100 is fully received in the heating chamber 202. The aerosol-generating device 250 further comprises a heater arrangement 203 and a power source 204 for supplying power to the heater arrangement 203. A controller (not shown) is also provided to control such supply of power to the heater arrangement 203. The heater arrangement 203 is configured to controllably heat the aerosol-generating article 100 during use, when the aerosol-generating article 100 is fully received within the heating chamber 202.

The heater arrangement 203 extends from an upstream end to a downstream end defining a heating zone. The heater arrangement 203 is the same length as the aerosolgenerating substrate reservoir 103 such that when the aerosol-generating article 100 is fully received within the heating chamber 202, the entire length of the aerosol-generating substrate reservoir 103 is received within the heating zone to provide optimal heating of the aerosolgenerating substrate reservoir 103. The heater arrangement 203 comprises a resistive heating element.

The ventilation zone 110 is arranged to be exposed when the aerosol-generating article 100 is fully received within the heating chamber 202.

In use, the aerosol-generating article 100 is fully received within the heating chamber 202 of the aerosol-generating device 250. The heater arrangement 203 is activated by the controller and the resistive heating element generates heat which is transferred directly to the aerosol-generating substrate reservoir 103 which is disposed within the heating zone. This generates an aerosol in the aerosol-generating substrate reservoir 103. When a pressure drop is applied to the downstream end 102 of the aerosol-generating article 100, air is drawn into the heating chamber 202 and into the aerosol-generating substrate reservoir 103. The aerosols generated in the aerosol-generating substrate reservoir 103 is entrained in the airflow which then passes through the downstream section before leaving through the downstream end 102 of the aerosol-generating article 100.

Figure 4 shows an aerosol-generating article 310 comprising a first planar external layer 324 forming a first planar external surface 321 , a second planar external layer 325 forming a second planar external surface 322, and a frame 350 positioned between the first planar external layer 324 and the second planar external layer 325. The first planar external layer 324 and the second planar external layer 325 may be formed from a non-aerosol forming material, such as paper or card. Alternatively, either of the first planar external layer 324 and the second planar external layer 325 may comprise an aerosol-generating substrate comprising an aerosol-generating material, for example tobacco.

The aerosol-generating article 310 has a length extending in the x-direction, a width extending in the y-direction and a thickness extending in the z-direction. The aerosolgenerating article 310 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 3.1 millimetres. The first planar external surface 321 and the second planar external surface 322 extend in the x-direction and the y-direction. That is, the first planar external surface 321 and the second planar external surface 322 extend in the x/y plane. The first planar external surface 321 is positioned parallel to the second planar external surface 322 and the first planar external surface 321 is spaced from the second planar external surface 322 in the z-direction or transverse direction. The distance between the first planar external surface 321 and the second planar external surface 322 in the z-direction or transverse direction corresponds to the thickness of the aerosol-generating article 310.

The aerosol-generating article 310 is a substantially flat aerosol-generating article or substantially planar aerosol-generating article. In particular, the thickness of the aerosolgenerating article 310 is less than 50 percent of both the length and the width of the aerosolgenerating article. The aerosol-generating article 310 has a generally rectangular cuboid shape and a laminated structure formed by the first planar external layer 324, the frame 350 and the second planar external layer 325. The first planar external layer 324, the frame 350 and the second planar external layer 325 are bonded together with an adhesive, in particular guar gum.

Figure 5 shows an exploded view of the aerosol-generating article 310 of Figure 4.

The frame 350 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 2.7 millimetres. The frame 350 is made from cardboard and defines a frame aperture extending through the thickness of the frame 350. The frame aperture at least partially forms a cavity 330. The cavity 330 has length of 26 millimetres, a width of 6 millimetres, and a thickness of 2.7 millimetres. Therefore, the cavity 330 has a volume of about 421.2 cubic millimetres. The cavity 330 is filled with a plurality of beads of aerosol-generating elements 10 in accordance with the present disclosure (shown schematically). The aerosol-generating elements fill the volume of the cavity 330 and airflow through the cavity 330 is provided by interstices between adjacent aerosol-generating elements 10.

The first planar external layer 324 and the second planar external layer 325 have a thickness of 200 micrometres and are in physical contact with the frame 350. The first planar external layer 324 and the second planar external layer 325 are bonded to the frame with an adhesive 315. The first planar external layer 324 overlies an end of the cavity 330 and forms a first cavity end wall 331. The second planar external layer 325 overlies an opposite end of the cavity 330 and forms a second cavity end wall 332. That is, the frame 350, the first planar external layer 324 and the second planar external layer 325 collectively define the cavity 330.

The frame 350 comprises a peripheral wall 351 that circumscribes the cavity 330. The peripheral wall 351 has a radial thickness of about 2 millimetres.

An air inlet (not visible) and an air outlet 312 are defined by, and extend through, the peripheral wall 351 of the frame 350. The air inlet is positioned opposite the air outlet 312, on the opposite wall of the frame 350. The air inlet and the air outlet 312 each have a rectangular cross-section, a width of 2 millimetres, and a thickness of 0.9 millimetres. An airflow passage extends between the air inlet and the air outlet 312 through the cavity 330. The air outlet 312 and portions of the aerosol-generating article wherein the air outlet 312 is formed may be described as forming part of a downstream section of the aerosol-generating article 310.

The aerosol-generating elements 10 have the shape and size described above with reference to the drawing of Figure 1. The total weight of the aerosol-generating elements in the cavity 330 is approximately 150 mg. Examples of suitable formulations for the aerosolgenerating elements 10 are described in more detail below.

Example A

An aerosol-generating solution is formed from a mixture of the following components:

In an initial step, the sodium alginate is added to water to form a matrix polymer solution. The nicotine is then added, followed by the glycerin and finally the levulinic acid.

The resultant aerosol-generating solution is extruded through a plurality of 0.58millimetre nozzles to form a plurality of droplets, which are then dropped from a height of 21 centimetres into a cross-linking solution having the following composition, at room temperature:

The droplets are left in the cross-linking solution with constant agitation at 200 rpm for a period of 22 minutes before being removed, rinsed and dried at 25 degrees Celsius for 12 hours, in a tray dryer. For rinsing, the removed elements are soaked for 5 minutes in distilled water or in a 50 percent by weight solution of isopropanol in distilled water. Rinsing the removed elements with isopropanol is especially effective at removing residual water or glycerin off the surface of the removed element. The resultant dried aerosol-generating elements are in the form of solid, substantially spherical beads having a diameter of about 1.5 millimetres. Each bead has a weight of approximately 1 .8 milligrams, a water activity of from 0.3 to 0.5 and the following composition:

Example B

Following the same method described in connection with Example A, dried aerosolgenerating elements are prepared in the form of solid, substantially spherical beads having a diameter of about 1.5 millimetres, each bead having a weight of approximately 1 .8 milligrams, a water activity from 0.3 to 0.5, and the following composition:

Comparative example

Following the same method described in connection with Example A, dried aerosolgenerating elements are prepared in the form of solid, substantially spherical beads having a diameter of about 1.5 millimetres, each bead having a weight of approximately 1.8 milligrams, a water activity from 0.3 to 0.5, and the following composition:

From a macroscopic, morphologic viewpoint it appears that aerosol-generating elements in accordance with the present invention (Examples A, B) are less sticky compared with the Comparative Example aerosol-generating elements. Without wishing to be bound by theory, the inventors hypothesize that the activated carbon in the aerosol-generating elements of the invention is capable of sorbing glycerin molecules that have therefore less of a tendency to migrate and be released from the aerosol-generating elements at room temperature. Thus, on top of being less sticky - which is beneficial in terms of ease of handling and therefore facilitates the incorporation of the aerosol-generating elements of the invention into an aerosolgenerating article or system - the aerosol-generating elements may also provide a more stable alternative to existing aerosol-generating elements as they are associated with reduced glycerin losses.

Thermal stability tests

The thermal stability of aerosol-generating elements prepared in accordance with Example B and with the Comparative Example, respectively, can be tested in a TG-MS oven by continuously heating the aerosol-generating elements at temperatures in the range from 200 to 250 degrees Celsius for a period of from 10 to 20 minutes, and measuring the diameter of the aerosol-generating element to assess whether the aerosol-generating elements shrink.

For the aerosol-generating elements prepared in accordance with Example B, a diameter reduction of about 19 percent is observed. By contrast, for the aerosol-generating elements prepared in accordance with the Comparative Example, a diameter reduction of 40 percent is observed. For the aerosol-generating elements prepared in accordance with Example B, a volume reduction of about 46 percent is observed. By contrast, for the aerosolgenerating elements prepared in accordance with the Comparative Example, a volume reduction of 78 percent is observed.

Without wishing to be bound by theory, it is understood that, because the activated carbon is substantially not compressible, the overall volume loss is significantly reduced in aerosol-generating elements in accordance with the present invention. Thermogravimetric analysis

The nicotine and glycerin release profile of the aerosol-generating elements prepared in accordance with Example B may be assessed in a thermogravimetric analysis (TGA). The TGA test is carried out using a thermogravimetric machine coupled to a mass spectrometer, or similar TGA equipment. In the analysis the aerosol-generating elements are heated from 25 degrees Celsius to 400 degrees Celsius in an inert nitrogen atmosphere with the temperature being increased at a rate of 15 degrees Celsius per minute and with an air flow of 60 ml per minute. As the temperature is increased, the release of nicotine and glycerin are assessed by detecting the respective molecules by way of a specific representative ions.

Data collected carrying out TGA tests on aerosol-generating elements in accordance with the invention can be compared with data collected carrying out an equivalent TGA test on aerosol-generating elements prepared in accordance with the and the Comparative Example. One such comparison may provide some information about release mechanisms and dynamics, which may be help fine tune delivery of aerosol species to a consumer when the aerosol-generating elements are incorporated in an aerosol-generating article or used as such in combination with an aerosol-generating device.

The nicotine and glycerin release profiles of aerosol-generating elements prepared in accordance with Example A was compared with the nicotine and glycerin release profiles of aerosol-generating elements produced in accordance with the Comparative Example by plotting the cumulative amount of nicotine and glycerin released by each batch of aerosolgenerating elements side by side.

The results of this comparison suggest that the inclusion of the activated carbon in the aerosol-generating elements tends to enhance the thermal release of nicotine and glycerin at lower temperatures.

The Comparative Example aerosol-generating elements began to release nicotine significantly only above 130 degrees Celsius, most of the menthol having been released by the time the temperature reached about 280 degrees Celsius. By contrast, the Example B aerosol-generating elements, containing 20 percent by weight of activated carbon, began to release nicotine significantly already at around 120 degrees Celsius, almost all the nicotine content having been released as temperature approached 245 degrees Celsius (a single derivative TG (DTG) peak is detected at around 217 degrees Celsius).

Further, the Comparative Example aerosol-generating elements began to release glycerin above 150 degrees Celsius, and continues to release glycerin well above 250 degrees, most of the glycerin having been released by the time the temperature reached about 280 degrees Celsius. By contrast, the Example B aerosol-generating elements, containing 20 percent by weight of activated carbon, similarly began to release glycerin significantly at around 150 degrees Celsius, yet almost all its nicotine content had been released as temperature approached 250 degrees Celsius (a single derivative TG (DTG) peak is detected at around 242 degrees Celsius).

It is known that at temperatures in the range from 200 to 250 degrees Celsius, alginate can begin to decompose and caramelise by forming complex cross-linked structures. Without wishing to be bound by theory, it is understood that in the case of the aerosol-generating elements prepared in accordance with the Comparative Example, where a significant fraction of the glycerin content has not yet been released at 250 degrees Celsius, the residual glycerin tends to remain trapped within the caramelised alginate structure, and so it is no longer available for delivery to the consumer. By contrast, in aerosol-generating elements in accordance with the invention, it appears that most of the glycerin has advantageously been released by the time the temperature reaches values such as to cause the irreversible degradation of the alginate matrix. This enables a more efficient use of the components of the aerosol-generating formulation and an improved aerosol delivery to the consumer during regular use of the aerosol-generating elements as part of an aerosol-generating article or directly with an aerosol-generating device.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 5% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

1 . An aerosol-generating element for use in an aerosol-generating article or system, the aerosol-generating element comprising: a solid continuous matrix structure; a solid porous substrate dispersed within the solid continuous matrix structure, the solid porous substrate comprising activated carbon; an aerosol-generating formulation also dispersed within the solid continuous matrix structure, wherein the aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element, a portion of the aerosol-generating formulation being sorbed in the solid porous substrate; wherein the solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers; wherein the aerosol-generating formulation dispersed within the solid continuous matrix structure comprises a polyhydric alcohol, a polyhydric alcohol content in the aerosolgenerating formulation trapped within the solid continuous matrix structure accounting for at least 40 percent by weight based on the total weight of the aerosol-generating element; and wherein the activated carbon content accounts for at least 5 percent by weight based on the total weight of the aerosol-generating element.

2. An aerosol-generating element according to claim 1 , wherein the solid porous substrate has a standard BET surface area of between 100 metres squared per gram and 600 metres squared per gram.

3. An aerosol-generating element according to any one of the preceding claims, wherein the solid porous substrate has a pore volume measured using adsorption isotherms of either carbon dioxide (VDR (CO2)) or nitrogen (VDR (N2)) of at least 0.05 cubic centimetres per gram.

4. An aerosol-generating element according to any one of the preceding claims, wherein the solid porous substrate has a pore volume measured using adsorption isotherms of either carbon dioxide (VDR (CO2)) or nitrogen ( DR (N2)) of no more than 0.35 cubic centimetres per gram.

5. An aerosol-generating element according to any one of the preceding claims, wherein the one or more matrix-forming polymers include at least one of alginate and pectin.

6. An aerosol-generating element according to claim 5, wherein the solid continuous matrix structure is an alginate matrix.

7. An aerosol-generating element according to any one of the preceding claims, wherein the aerosol-generating formulation trapped within the solid continuous matrix structure further comprises nicotine or anatabine.

8. An aerosol-generating element according to any one of the preceding claims, wherein the aerosol-generating formulation trapped within the solid continuous matrix structure further comprises an acid.

9. An aerosol-generating element according to claim 8, wherein the acid is selected from the group consisting of lactic acid, levulinic acid, benzoic acid, citric acid, fumaric acid and combinations thereof.

10. An aerosol-generating element according to any one of the preceding claims further comprising at least 0.05 percent by weight of a cross-linking agent.

11. An aerosol-generating element according to claim 10, wherein the cross-linking agent comprises a cross-linking solution of multivalent cations.

12. An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising: an aerosol-generating element according to any of claims 1 to 11 , and a downstream section downstream of the aerosol-generating element, the downstream section comprising an aerosol-cooling element comprising a hollow tubular element and a mouthpiece element downstream of the aerosol-cooling element.

13. An aerosol-generating system for producing an inhalable aerosol, the system comprising: aerosol-generating article according to claim 12, and an aerosol-generating device comprising a heating arrangement.

14. A cartridge for an aerosol-generating system, the cartridge comprising: an aerosol-generating element according to any of claims 1 to 11 , a heating arrangement comprising: an electrical heating element arranged to heat at least a portion of the aerosolgenerating element to generate an aerosol, and at least one cartridge electrical contact arranged to engage with corresponding at least one device electrical contact of an aerosol-generating device.

15. An aerosol-generating system for producing an inhalable aerosol, the system comprising: a cartridge according to claim 14, and an aerosol-generating device, the aerosol-generating device comprising a power supply and at least one device electrical contact.