WO2025041096A1

WO2025041096A1 - Atomizer device

Info

Publication number: WO2025041096A1
Application number: PCT/IB2024/058221
Authority: WO
Inventors: Wietze Nijdam; Henri Joseph Van Egmond; Cornelis Johannes Maria Van Rijn
Original assignee: Medspray BV
Current assignee: Medspray BV
Priority date: 2023-08-24
Filing date: 2024-08-23
Publication date: 2025-02-27
Anticipated expiration: 2026-02-24
Also published as: NL2035668B1

Abstract

An atomizer device comprises an atomizer body (30, 32) with at least one continuous atomizing opening (35). The atomizing opening (35) receives a liquid for atomizing under increased pressure and opens in order to dispense a mist in the form of a mist jet of miniscule liquid droplets from the liquid. A porous absorption body is arranged downstream of he atomizing opening and comprises a passage for the mist jet bounded by an edge of the absorption body. The edge of the absorption body lies at least partially within an initial droplet size from the atomizer body.

Description

Atomizer device

The present invention relates to an atomizer device, comprising an atomizer body with at least one atomizing opening which is intended and configured to receive a liquid for atomizing under increased pressure on an inlet side and to dispense a mist jet thereof along a path, which mist jet comprises minuscule droplets of the liquid.

Such an atomizer device is for instance known from EP3383548 and is based on so-called Plateau-Rayleigh instability of a liquid flow which is guided through a thin channel, also referred to as Rayleigh scattering. In the present device this channel is provided by an atomizing opening of the at least one atomizing opening. This is a phenomenon in fluid dynamics wherein a cylindrical liquid column becomes unstable under determined conditions and splits up into a series of smaller droplets. The driving force behind this is the surface tension of the liquid, which aims to minimize the liquid column and to separate droplets of roughly equal size therefrom in each case. Given the constant viscosity of the liquid, this size is in turn determined mainly by the physical dimensions of the atomizing opening, which are set in the construction. With such a device a substantially monodisperse mist can thus be realized, which is composed of only drops of roughly identical size. A high-grade mist composed of minuscule droplets of roughly equal size is desirable for numerous applications. The above described device is eminently suitable therefor, but requires for this purpose relatively narrow atomizing openings and a relatively high liquid pressure in order to overcome the resistance thereof. A common phenomenon is here that during a starting stage the pressure buildup is still insufficient to form a fine mist from the liquid. Instead, a macroscopic liquid droplet forms at the surface of the atomizer, which droplet escapes from the surface as such.

This results in an incorrect and unintended initial deposition of the liquid. Drawbacks hereof can vary from discomfort, for instance in the eye from an eye spray, to material stains or reduced efficacy as a result of a deposition of such a starting droplet instead of a fine spray. The starting pressure of the device is also higher than strictly necessary, which is undesirable for various reasons.

The present invention has for its object, among others, to prevent such leaking away of the initial liquid, also referred to as drooling, in an atomizer device.

In order to achieve the stated object an atomizer device of the type described in the preamble has the feature according to the invention that a porous absorption body with a passage for the mist jet bounded by an edge of the absorption body is arranged downstream of the atomizing opening, and that the edge of the absorption body lies at least partially within an initial droplet size from the atomizer body.

In use of the atomizer device pressure will initially build up in the liquid, although this pressure is not yet high enough to form the liquid into a mist jet. Instead, a droplet forms on the surface. This droplet grows until it touches the porous material of the absorption body, which is for this purpose provided within a distance the size of the initial droplet from the atomizing opening. The droplet is soaked up by the porous material. The surface tension of the liquid ensures that the droplet is absorbed wholly by the porous material. As soon as the pressure is sufficient for Rayleigh scattering of the liquid jet a "dry", i.e. nonspattering, mist jet is formed, which escapes the absorption body owing to the passage which is for this purpose provided in the absorption body with sufficiently large dimensions.

The porous absorption body, which flanks the atomizing opening downstream in at least an orthogonal projection, provides for capture the initial liquid if this liquid were to form an excessively large droplet, which could otherwise be experienced as an undesirable splash or drip. Instead, any excess of liquid is soaked up by the absorption body and discharged in controlled manner. The liquid is thereby given no opportunity to drip or splash off the device. The initial liquid thus particularly does not form any barrier to the further liquid either, so that a normal energy (pressure) suffices therefor to generate a "dry" mist jet which breaks up into successive minuscule, at least substantially identical droplets of a defined size. The liquid that was soaked into the absorption body will finally evaporate, whereby no saturation will occur.

The edge of the passage is situated outside the path of the mist jet, so that normal operation of the atomizer device is not impeded by the presence of the absorption body. With this in mind, a preferred embodiment of the atomizer device has the feature according to the invention that the passage has a larger size than the atomizing opening, particularly a size at least several times larger, more particularly a size at least ten times larger, and preferably a size at least a hundred times larger. Such a relatively wide passage provides ample clearance for the final mist jet to pass therethrough intact.

It has been found that expulsion of the initial liquid, away from the atomizing opening, is enhanced if the initial liquid is attracted asymmetrically. This creates an imbalance which results in a more directed expulsion toward the edge of the passage which is closest in that case. With this in mind, a preferred embodiment of the atomizer device has the feature according to the invention that the atomizing opening lies eccentrically relative to a central axis of the passage. For the purpose of said eccentric positioning, the atomizer body can be arranged off-centre relative to the passage, but the atomizing opening can also be provided eccentrically in the atomizer body. In both cases the edge of the passage in the absorption body lies closer to the atomizing opening on at least one side than elsewhere. The initial liquid will therefore be attracted mainly to this side.

The initial liquid builds up into an asymmetrical droplet. As soon as the energy of the liquid is high enough, the droplet is launched off the atomizer surface and leaves behind a "dry" droplet jet. Before being launched, the droplet will still cling to the surface of the atomizer body temporarily, but obtains a lateral speed component owing to the eccentric positioning of the atomizing opening. As soon as the droplet is launched, the droplet is deflected thereby. This provides an option of catching the droplet outside the target area of the "dry" droplet jet. A particular embodiment of the atomizer device according to the invention, characterized in that the absorption body is arranged spatially separated from the atomizer body, is suitable for this purpose.

In order to allow unimpeded passage of the final mist jet the edge of the passage must keep a sufficient distance therefrom. An eccentric positioning of the atomizing opening relative to this passage makes the nearest part of the edge of the passage the most critical in this respect. In order to nevertheless be able to provide free passage under all circumstances a further particular embodiment of the atomizer device has the feature according to the invention that the atomizing opening is configured to dispense the mist jet obliquely along a path oriented toward the central axis. The mist jet thus moves further away from the nearest part of the edge of the passage as the distance of the jet relative to the atomizing opening increases, thus drastically reducing the chances of collision with this part of the edge.

In a further particular embodiment the atomizer device has the feature according to the invention that the absorption body is formed from an attracting porous material, particularly a hydrophilic, hydrophobic or amphiphilic material, adapted to the liquid for atomizing. From a viewpoint of a simple assembly a further preferred embodiment of the atomizer device according to the invention has in this respect the feature that the absorption body comprises a disc-shaped foam body, fibre body or sponge body. Such a disc body can be handled and mounted in practical manner.

Good results have been obtained with a particular embodiment of the atomizer device according to the invention, characterized in that the disc body comprises a microscopic open pore structure with a porosity of at least 30%, particularly at least 50%, more particularly with substantially only pores smaller than 100 micrometres. This material has a sufficiently strong capillary action to absorb the initial droplet quickly and effectively before the operating pressure of the atomizer device has built up fully and the "dry" mist jet commences.

Many materials and combinations of materials are suitable for the porous absorption body, yet use is preferably made according to the invention of a foam body of polyurethane or of a fibre body formed from glass fibres or polymer fibres, particularly polymer fibres of polyurethane, polyamide and/or polypropylene.

The atomizer device according to the invention allows a high degree of miniaturization of the atomizer body, to the size of millimetres or even smaller. In order to nevertheless enable practical handling, assembly and manipulation of the atomizer device here a particular embodiment of the atomizer device has the feature according to the invention that the atomizer body is arranged recessed in a holder and is surrounded downstream by a wall of the holder, and that the wall of the holder supports the absorption body. In a further particular embodiment the atomizer device is characterized here in that one of the passage in the absorption body and the atomizing opening lies eccentrically in the recess. Owing to such an asymmetrical assembly, the atomizing opening will ultimately lie closer to a first part of the edge of the passage than to a remaining part, whereby an increased effectiveness of the absorption body is achieved.

The wall on the side directed toward the atomizing opening can advantageously be covered with a coating, particularly a hydrophilic, hydrophobic or amphiphilic coating, adapted to the liquid for atomizing, so that the initial droplet will be attracted thereby and will be led away from the atomizing opening.

The atomizer device can be manufactured with an extremely high degree of precision, wherein use is advantageously made of current photolithographic semiconductor techniques. A further particular embodiment of the atomizer device has for this purpose the feature that the atomizer body comprises a carrier body, particularly of a semiconductor material such as silicon, which is covered with a relatively thin membrane layer, particularly of a ceramic material such as silicon nitride, in which the atomizing opening is formed, wherein the carrier body comprises a cavity which is spanned by the membrane layer and which is in fluid connection with the inlet of the atomizing opening. The invention will be further elucidated hereinbelow with reference to an exemplary embodiment and an accompanying drawing. In the drawing: Figure 1 shows an exemplary embodiment of an atomizer device;

Figure 2 shows a first exemplary embodiment of an atomizer device according to the invention in an initial stage of operation;

Figure 3 shows the atomizer device of figure 2 in a further stage of operation;

Figure 4 shows a second exemplary embodiment of an atomizer device according to the invention; and

Figure 5 shows a third exemplary embodiment of an atomizer device according to the invention.

It is otherwise noted here that the figures are purely schematic and not all drawn to (the same) scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are designated in the figures with the same reference numeral.

The device shown in figure 1 comprises a plastic holder 10 in which an atomizer body 30 is arranged in recessed manner. In this example the holder is an injection-moulded part which can be manufactured from a thermoplastic plastic such as polyethylene, polyamide or polypropylene. The atomizer body 30 is here fixed on both sides by a seat 14 which was formed by a melted and subsequently solidified part of the holder wall by supplying heat and mechanical impact. Atomizer body 30 thus forms a bottom of a cup-like recess 15 in the holder 10. On an opposite side the holder 10 provides a feed cavity 12 for a liquid under increased pressure. One or more filters can be placed in feed cavity 12 as desired in order to stop any solid particles in the liquid, which could otherwise block the atomizer body or adversely affect it in other manner.

In this example the atomizer body comprises a carrier body 30 of silicon, in which a continuous cavity 31 is formed by means of etching while masking with an etching mask. Use can be made for this purpose of highly precise photolithographic techniques as are standard in current semiconductor technology. Both the location and the size of the cavity 31 are thus precisely determined. The carrier body 30 was removed from a standard silicon wafer by sawing, breaking and/or (laser) cutting, and therefore typically has a thickness of several hundred microns.

A relatively thin membrane layer 32 of silicon nitride, which is optionally separated from carrier body 30 by a thin silicon oxide layer (not shown) obtained through oxidation, is deposited on the surface of carrier body 30 from a chemical vapour phase, likewise using semiconductor technology. A -li- continuous atomizing opening 35 through which the liquid can escape is etched into the membrane layer 32. The atomizing opening 35 typically has a diameter in the order of one micrometre to several tens of micrometres. The nitride layer 32 is typically one to several micrometres thick, this also determining a length of the channel through atomizing opening 35.

This channel in atomizing opening 35 forces the liquid supplied under pressure into the form of a thin cylinder which will finally break up into a series of successive droplets 20 of substantially equal size as a result of so-called Plateau- Rayleigh instability. This forms an individual mist jet from the spray to be created with the atomizer device. In order to supply a mist with a wide spray pattern and/or to achieve an increased liquid flow rate the atomizer body 30 can be embodied with one or more of such atomizing openings, wherein atomizing openings are distributed over a number of separate cavities 31 and/or can be arranged collectively per cavity 31.

The liquid pressure required for the Plateau-Rayleigh scattering is still developing at the start of the device, whereby the liquid will initially only accumulate at the surface of the atomizer body and a microscopic droplet 25 of the liquid may form there. In order to prevent this droplet 25 from being entrained in the created spray the atomizer device is provided in the example of figures 2 and 3 with a porous absorption body 40 which has an attractive action on the initial liquid and is able and configured to absorb the liquid.

For the absorption body use is made of a microporous polyurethane foam with an open pore structure. The applied foam is formed into a disc body and has a porosity in the order of at least 30 to 50% with pores in the order of 20 to 100 micrometres effective diameter, calculated on the basis of a perfect sphere of the same volume. A fibre body formed from glass fibres or polymer fibres, particularly polymer fibres of polyurethane, polyamide and/or polypropylene, with a similar porosity and open structure which allows a capillary action on the liquid can instead also be applied. Such microporous materials with sufficient absorption capacity are commercially available under the brand name Sporex.

The absorption body 40 is spatially separated from the atomizing opening 35 and provides a passage 45 which is many times greater than the atomizing opening 35 itself, so that mist jet 20 will not be impeded thereby. The passage 45 typically has a diameter in the order of several tenths of a millimetre to several millimetres. In this example the size of the passage is about 1300 micrometres. The absorption body lies here within a distance h from the atomizing opening. This dimension h corresponds with the maximum dimension, i.e. height, of the initial droplet 25, as calculated from the surface. The initial liquid initially swells to a droplet 25 which will finally reach an edge 45 of porous body 40 and will be soaked up thereby, see figure 2. The porous body 40 is situated outside a path of the mist jet 20 to be supplied, which will therefore remain unaffected by the presence of the porous body, see figure 3. The soaked-up droplet 25 remains captured in porous body 40 and will finally disappear therefrom through evaporation. For an improved absorption and retention of the absorbed liquid a hydrophobic or hydrophilic material is preferably opted for for the porous body 40, depending on the nature of the liquid 25 to be absorbed.

A second exemplary embodiment of an atomizer device according to the invention is shown by figure 4. This embodiment is largely the same as that of the preceding example in respect of its construction. In this example the atomizing opening 35 is situated eccentrically, i.e. outside a central axis, in the recess 15 of holder 10. In this case the atomizing opening is formed eccentrically in atomizer body 32 for this purpose. Alternatively, the atomizer body 30, 32 can also be placed eccentrically in holder 10 and/or the passage 45 can be provided eccentrically. The passage 45 of absorption body 40 thereby lies out of line with atomizing opening 35, so that a part of the edge thereof lies closer to the atomizing opening than the remaining part of the edge. Atomizing opening 35 typically lies offset relative to the central axis H of passage 45 in the order of a minimum of 20 to 50 micrometres, centre-to-centre.

Owing to this asymmetrical positioning, the initial droplet 25 will experience a net attraction to the nearest side; to the right in the shown example. This can be contributed to further by adapting the material of holder 10 and/or that of the surface of atomizer body 30, 32 to the nature of the liquid for atomizing, or covering it with a coating adapted thereto. This will result in initial droplet 25 growing asymmetrically; more to the right than to the left in the drawing.

If the energy of the liquid is high enough, droplet 25 is launched off the atomizer body 30, 32 and a "dry" mist jet 20 remains. During launching, optionally aided by interaction with the wall of holder 10, droplet 25 will still cling to surface 32 to some extent and thereby obtains a lateral speed component. This causes droplet 25 to deflect and be caught by absorption body 40, which is for this purpose provided spatially separated within reach of the droplet. The passage 45 provided in absorption body 40 then allows unimpeded passage to the "dry" mist jet.

Figure 5 shows a third embodiment of the atomizer device according to the invention. Use is in this case also made of an asymmetrical, eccentric positioning of the atomizing opening 35 and the passage 45 in the absorption body relative to each other. With a view to a greater clearance of the mist jet relative to the relatively nearby edge of passage 45 however, the atomizing opening is intentionally configured such that it will dispense a mist jet oriented obliquely toward the central axis H of the passage. In this case the mist jet passes the absorption body lying at a distance at a greater distance from the edge of the passage 45 therein.

Although the invention has been further elucidated above with reference to only a single exemplary embodiment, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art.

Claims

Claims:

1 . Atomizer device, comprising an atomizer body with at least one atomizing opening which is intended and configured to receive a liquid for atomizing under increased pressure on an inlet side and to dispense a mist jet thereof along a path, wherein the mist jet comprises minuscule droplets of the liquid, characterized in that a porous absorption body with a passage for the mist jet bounded by an edge of the absorption body is arranged downstream of the atomizing opening, and that the edge of the absorption body lies at least partially within an initial droplet size from the atomizer body.

2. Atomizer device according to claim 1, characterized in that the passage has a larger size than the atomizing opening, particularly a size at least several times larger, more particularly a size at least ten times larger, and preferably a size at least a hundred times larger.

3. Atomizer device according to claim 1 or 2, characterized in that the atomizing opening lies eccentrically relative to a central axis of the passage.

4. Atomizer device according to claim 3, characterized in that the atomizing opening is configured to dispense the mist jet along a path oriented toward the central axis.

5. Atomizer device according to one or more of the preceding claims, characterized in that the absorption body is arranged spatially separated from the atomizer body.

6. Atomizer device according to one or more of the preceding claims, characterized in that the absorption body is formed from an attracting porous material, particularly a hydrophilic, hydrophobic or amphiphilic material, adapted to the liquid for atomizing.

7. Atomizer device according to one or more of the preceding claims, characterized in that the absorption body comprises a disc-shaped foam body, fibre body or sponge body.

8. Atomizer device according to claim 7, characterized in that the disc body comprises a microscopic open pore structure with a porosity of at least 30%, particularly at least 50%, more particularly with substantially only pores smaller than 100 micrometres.

9. Atomizer device according to claim 7 or 8, characterized in that the disc body comprises a foam body of polyurethane.

10. Atomizer device according to claim 7 or 8, characterized in that the disc body comprises a foam body formed from glass fibres or polymer fibres, particularly polymer fibres of polyurethane, polyamide and/or polypropylene.

11. Atomizer device according to one or more of the preceding claims, characterized in that the atomizer body is arranged recessed in a holder and is surrounded downstream by a wall of the holder, and that the wall of the holder supports the absorption body.

12. Atomizer device according to claim 11, characterized in that the wall is covered with a coating, particularly a hydrophilic, hydrophobic or amphiphilic coating, adapted to the liquid for atomizing.

13. Atomizer device according to claim 11 or 12, characterized in that one of the passage in the absorption body and the atomizing opening lies eccentrically in the recess.

14. Atomizer device according to one or more of the preceding claims, characterized in that the atomizer body comprises a carrier body, particularly of a semiconductor material such as silicon, which is covered with a relatively thin membrane layer, particularly of a ceramic material such as silicon nitride, in which the atomizing opening is formed, wherein the carrier body comprises a cavity which is spanned by the membrane layer and which is in fluid communication with the inlet of the atomizing opening.