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WO2011045777A1 - Procédé de production d'un film polymère contenant un réseau de cavités - Google Patents

Procédé de production d'un film polymère contenant un réseau de cavités Download PDF

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Publication number
WO2011045777A1
WO2011045777A1 PCT/IE2010/000058 IE2010000058W WO2011045777A1 WO 2011045777 A1 WO2011045777 A1 WO 2011045777A1 IE 2010000058 W IE2010000058 W IE 2010000058W WO 2011045777 A1 WO2011045777 A1 WO 2011045777A1
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WIPO (PCT)
Prior art keywords
film
environment
solution
film solution
polymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IE2010/000058
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English (en)
Inventor
John Boland
Ronan Daly
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
College of the Holy and Undivided Trinity of Queen Elizabeth near Dublin
Original Assignee
College of the Holy and Undivided Trinity of Queen Elizabeth near Dublin
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Publication of WO2011045777A1 publication Critical patent/WO2011045777A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1225—Basic optical elements, e.g. light-guiding paths comprising photonic band-gap structures or photonic lattices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/15—Use of additives
    • B01D2323/18—Pore-control agents or pore formers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/42—Details of membrane preparation apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/021—Pore shapes

Definitions

  • the present invention relates to a method for producing a polymer film with an array of cavities therein, and to a polymer film produced by the method.
  • Films comprising arrays of cavities of micron and sub-micron size are required in many fields of technology, for example, in photonics, in microfluidics and other technological fields where cavities of micron and sub-micron sizes are required.
  • films comprising cylindrical cavities of micron and sub-micron sizes are used as photonic light delays and filters, as are spherical cavities and cavities of other shapes.
  • such films comprising cavities of micron and sub-micron sizes are formed of silicon, glass, quartz and the like, and the cavities are formed using reactive ion etching, electrochemical processes and electron beam lithography. The cavities thus formed are then coated or
  • a method for producing a photonic crystal material which requires initially producing a porous template of polymer material.
  • a polymer an oligomer or a non-polymeric organic substance is dissolved in a volatile solvent to form an evaporative solution.
  • a film of the solution is deposited on a substrate, and a moisture containing gas is passed over the film solution in order to evaporate the solvent.
  • Moisture in the gas condenses on the surface of the film solution to form water droplets in an ordered array, which in turn sink into the film solution to form spherical water filled voids.
  • the present invention is directed towards providing such a method, and the invention is also directed towards providing a polymer film comprising an array of cavities.
  • a method for producing a polymer film with an array of cavities therein comprising forming a film of a polymer/solvent solution on a substrate, subjecting the film solution to a first environment adjacent a gas/film interface of the film solution, the first environment being adapted to accelerate solvent evaporation from the film solution through the gas/film interface of the film solution to establish a polymer concentration gradient in the film solution with the polymer concentration decreasing in a direction into the film solution from the gas/film interface so that the polymer concentration gradient is suitable for facilitating growth of liquid droplets into the film solution through the gas/film interface, subjecting the film solution to a second environment adjacent the gas/film interface thereof on establishment of the polymer concentration gradient, the second environment being adapted to condense a liquid on the gas/film interface surface to form droplets of the liquid thereon with the droplets growing into the film solution through the gas/film interface to form the cavities, and subjecting the film solution adjacent the gas film interface thereof to a third environment adapted to inhibit further drop
  • the glass transition temperature of a polymer or other material is the temperature at which the material loses its glass-like, more rigid properties and becomes rubbery and more flexible in nature.
  • the rate of evaporation of the solvent from the film solution is controlled by the third environment so that when the droplets no longer solely determine the shape and size of the cavities, the level of the solvent remaining in the film solution is sufficient to maintain the glass transition temperature of the film solution adjacent the bases of the cavities below the actual temperature of the film solution adjacent the bases of the cavities.
  • the film solution is subjected to the third environment until substantially all of the solvent is evaporated from the
  • the film solution is subjected to the third environment when the cavities formed by the droplets extend into the film solution to a predefined depth.
  • the film solution is subjected to the third environment when the cavities formed by the droplets are of a predefined size.
  • the third environment is of relative humidity which is adapted to control the vapour-liquid equilibrium adjacent the droplet interface with the third environment for evaporation of the droplets.
  • the relative humidity of the third environment is lower than the relative humidity of the second environment.
  • the relative humidity of the third environment does not exceed the relative humidity of the first environment.
  • the relative humidity of the third environment is similar to or lower than the relative humidity of the first environment.
  • the third environment comprises a gaseous medium of relative humidity lying in the range of 0% to 50%.
  • the relative humidity of the gaseous medium of the third environment lies in the range of 0% to 20%.
  • the relative humidity of the gaseous medium of the third environment lies in the range of 0% to 10%.
  • the velocity of the gaseous medium of the final gas flow adjacent the gas/film interface lies in the range of 0 metres per second to 0.4 metres per second.
  • the velocity of the gaseous medium of the final gas flow adjacent the gas/film interface lies in the range of 0.03 metres per second to 0.29 metres per second.
  • the velocity of the gaseous medium of the final gas flow adjacent the gas/film interface is approximately 0.06 metres per second.
  • the gaseous medium of the third environment comprises nitrogen.
  • water vapour is entrained in the gaseous medium of the third environment to produce the third environment to be of the appropriate relative humidity.
  • the first environment is adapted to control evaporation of the solvent from the film solution to produce a surface temperature at the gas/film interface to facilitate formation of the droplets thereon when the film solution is subjected to the second environment.
  • the first environment is adapted to control evaporation of the solvent from the film solution to produce a surface temperature at the gas/film interface of the film solution not greater than the dew point temperature of the second environment when the film solution is subjected to the second environment, and preferably, below the dew point temperature of the second environment.
  • the relative humidity of the first environment is controlled to be below a value at which liquid would condense out of the first environment onto the gas/film interface of the film solution.
  • the first environment comprises a gaseous medium of relative humidity lying in the range of 0% to 85%.
  • the relative humidity of the gaseous medium of the first environment lies in the range of 0% to 45%.
  • the relative humidity of the gaseous medium of the first environment lies in the range of 0% to 5%.
  • gaseous medium of the first environment is passed over the gas/film interface of the film solution as an initial gas flow during the period during which the film solution is subjected to the first environment.
  • the velocity of the gaseous medium of the initial gas flow adjacent the gas/film interface of the film solution lies in the range of 0.03 metres per second to 1.14 metres per second.
  • the velocity of the gaseous medium of the initial gas flow adjacent the gas/film interface of the film solution lies in the range of 0.17 metres per second to 0.57 metres per second.
  • the velocity of the gaseous medium of the initial gas flow adjacent the gas/film interface of the film solution is approximately 0.29 metres per second.
  • At least one of the relative humidity and the velocity of the gaseous medium of the initial gas flow is set to establish an evaporation rate of the solvent from the polymer/solvent solution to produce a surface temperature of the film solution adjacent the gas/film interface not greater than the dew point temperature of the second environment prior to the
  • At least one of the relative humidity and the velocity of the gaseous medium of the initial gas flow is set to establish an evaporation rate of the solvent from the polymer/solvent solution to produce a surface temperature of the film solution adjacent the gas/film interface below the dew point temperature of the second environment prior to the film solution being subjected to the second environment.
  • the gaseous medium of the first environment is nitrogen.
  • water vapour is entrained in the gaseous medium of the first environment to produce the first environment to be of the appropriate relative humidity.
  • the relative humidity of the second environment is adapted to control the vapour-liquid equilibrium adjacent the droplet interface with the second environment for controlling the rate of growth of droplets into the film solution.
  • the relative humidity of the second environment is controlled for controlling the progression of solvent evaporation from the film solution, and in turn for controlling the polymer concentration gradient in the film solution.
  • the relative humidity of the second environment is greater than the relative humidity of the first environment.
  • the relative humidity of the second environment is determined by the depth to which the cavities are required to extend into the polymer/solvent solution and the required transverse cross-section of the cavities.
  • the second environment is produced by subjecting the gas/film interface of the film solution to a gaseous medium of relative humidity lying in the range of 15% to 100%.
  • the relative humidity of the gaseous medium of the second environment lies in the range of 40% to 90%.
  • the relative humidity of the gaseous medium of the second environment lies in the range of 50% to 85%.
  • the gaseous medium of the second environment is passed over the gas/film interface of the film solution as an intermediate gas flow during the period during which the film solution is subjected to the second environment.
  • the flow rate of the gaseous medium of the intermediate gas flow over the gas/film interface of the film solution is controlled for controlling the progression of solvent evaporation from the film solution.
  • the velocity of the gaseous medium of the intermediate gas flow adjacent the gas/film interface of the film solution lies in the range of zero metres per second to 0.4 metres per second.
  • the velocity of the gaseous medium of the intermediate gas flow adjacent the gas/film interface of the film solution lies in the range of 0.03 metres per second to 0.29 metres per second.
  • the velocity of the gaseous medium of the intermediate gas flow adjacent the gas/film interface of the film solution is approximately 0.06 metres per second.
  • the duration during which the film solution is subjected to the second environment is determined by the size to which the cavities are to be formed.
  • the polymer/solvent solution is prepared so that the level of solvent in the polymer/solvent solution is such that the level of the solvent in the polymer/solvent solution does not fall below a level which would result in the glass transition temperature of the polymer solution rising above the temperature of the film solution during the period in which the film solution is being subjected to the first and second environments, and during the period of the third environment when the film solution is being subjected to the third environment until local polymer flow adjacent the cavities for determining the shape of the cavities is completed.
  • the invention also provides a polymer film having an array of cavities therein, the polymer film being formed by a method according to the invention.
  • a particularly important advantage of the invention is that the latter part of the formation of the cavities is controlled, and is controlled to the extent that the final shape of the cavity can be controlled.
  • cavities with relatively flat bases for example, cylindrical cavities with flat bases, can be produced, as well as cavities which are bulbous towards their lower end, and such bulbous cavities may also be produced with relatively flat bases.
  • the method according to the invention provides more control over the formation of the cavities, and in particular, the method according to the invention provides more control over the latter stages of formation of the cavities.
  • Fig. 1 is a schematic representation of apparatus for carrying out the method according to the invention for producing an array of cavities in a polymer film
  • Fig. 2 is a transverse cross-sectional side elevational view of a portion of the apparatus of Fig. 1 ,
  • Figs. 3 is a photomicrograph of a portion of a polymer film having cavities formed therein by the method according to the invention
  • Figs. 4 is a photomicrograph of a portion of a polymer film having cavities formed therein by the method according to the invention
  • Figs. 5 is a photomicrograph of a portion of a polymer film having cavities formed therein by the method according to the invention
  • Figs. 6(a) and (b) are photomicrographs of a portion of a polymer film having cavities formed therein by the method according to the invention
  • Fig. 7 is a graphical representation of the relative humidity of a gaseous medium plotted against time used in the method according to the invention for producing the polymer film of Fig. 3,
  • Fig. 8 is a graphical representation of the relative humidity of a gaseous medium plotted against time used in the method according to the invention for producing the polymer film of Fig. 4,
  • Fig. 9 is a graphical representation of the relative humidity of a gaseous medium plotted against time used in the method according to the invention for producing the polymer film of Fig. 5,
  • Fig. 10 is a graphical representation of the relative humidity of a gaseous medium plotted against time used in the method according to the invention for producing the polymer film of Fig. 6
  • Fig. 11 is a graphical representation of the glass transition temperature of the polymer/solvent solution plotted against the concentration of solvent as a percentage of mass in the polymer/solvent solution,
  • Fig. 12 illustrates two graphs, one graph being a plot of the concentration of polymer in the polymer/solvent solution against time, and the other being a plot of the glass transition temperature of the polymer/solvent solution against time during the production of a polymer film,
  • Fig. 13 is a photomicrograph of a portion of a polymer film having cavities formed therein by the method according to the invention
  • Fig. 14 is a photomicrograph of a portion of another polymer film having cavities formed therein by the method according to the invention.
  • Figs. 15 and 16 are graphical representations of the relative humidity of a gaseous medium plotted against time used in the method according to the invention for producing the polymer films of Figs. 13 and 14, respectively.
  • the polymer films 1 are produced by a method according to the invention, which will be described below, and each comprises a plurality of cavities 2 of respective different shapes, but being generally of circular transverse cross-section extending downwardly into the polymer films 1 from a top surface 3 thereof.
  • the cavities 2 in each of the films 1 are arranged in a hexagonally close-packed array.
  • the cavities 2 of each polymer film 1 converge to respective necks 4 adjacent the top surface 3 of each polymer film 1 to define open mouths 7 to the cavities 2.
  • the polymer films 1 are formed from an initial polymer/solvent solution which is drop-cast onto a substrate 5 as will be described below to form a thin film 6 of the polymer/solvent solution, as will also be described below with reference to Figs. 1 and 2.
  • the film solution 6 on the substrate 5 is subjected sequentially to three environments, namely, first, second and third environments, which are provided by passing a gaseous medium, in this case an inert gas, which in this embodiment of the invention is nitrogen gas entrained with water vapour over a top surface 8 of the film solution 6 on the substrate 5.
  • the top surface 8 of the film solution 6 is the surface which forms the top surface 3 of the polymer film 1 on completion of the formation of the polymer films 1.
  • the first environment is provided by passing an initial gas flow of the nitrogen gas with entrained water vapour over the top surface 8 of the film solution 6.
  • the initial gas flow the amount of water vapour entrained in the nitrogen is relatively low, so that the relative humidity of the initial gas flow is similarly relatively low.
  • the second environment to which the film solution 6 is subjected is provided by an intermediate gas flow which is passed over the top surface 8 of the film solution 6.
  • the intermediate gas flow comprises the nitrogen gas with entrained water vapour therein in order to produce a gas flow of a relatively high relative humidity, and considerably higher than the relative humidity of the initial gas flow.
  • the third environment to which the film solution 6 is subjected is provided by a final gas flow, which is passed over the top surface 8 of the film solution 6 and comprises nitrogen gas with entrained water vapour.
  • the amount of water vapour entrained in the final gas flow is set so that the relative humidity of the final gas flow is lower than the relative humidity of the intermediate gas flow.
  • the initial gas flow is provided to initiate solvent evaporation from the film solution 6 in order to reduce the surface temperature at the top surface 8 of the film solution 6 for the purpose of promoting the formation of water droplets on the top surface 8 during the intermediate gas flow.
  • the relative humidity and the velocity of the gas of the initial gas flow over the top surface 8 of the film solution 6 are set such as to minimise, and in general, to eliminate the formation of condensation on the top surface 8 of the film solution 6 during the initial gas flow.
  • the relative humidity and the velocity of the gas of the initial gas flow over the top surface 8 of the film solution 6 are also set to establish a polymer concentration gradient within the film solution 6 in which the polymer concentration decreases downwardly into the film solution 6 from the top surface 8.
  • the polymer concentration gradient in the film solution 6 is established so that the top surface 8 of the film solution 6 is capable of supporting water droplets as they form on the top surface 8 during the intermediate gas flow, and to control the rate of growth of water droplets into the film solution 6 through the top surface 8 to form the cavities 2.
  • the relative humidity and the velocity of the gas of the intermediate gas flow across the top surface 8 of the film solution 6 are set to control the vapour-liquid equilibrium adjacent the droplet interface with the gaseous medium of the intermediate gas flow in order to promote condensation on the top surface 8 of the film solution 6 to in turn form water droplets arranged in a hexagonally close-packed array. Controlling the vapour-liquid equilibrium adjacent the droplet interface with the gaseous medium of the intermediate gas flow facilitates control of the rate of formation of the droplets, as well as the rate of evaporation of the solvent from the film solution 6 to in turn control the polymer concentration gradient in the film solution 6.
  • the relative humidity and the velocity of the intermediate gas flow is controlled so that the rate of solvent evaporation from the polymer/solvent solution is sufficient to maintain the temperature at the top surface 8 of the film solution 6 below the dew point temperature of the gaseous medium of the intermediate gas flow.
  • the rate at which the water droplets grow into the film solution 6 through the top surface 8 is controlled. This, thus, permits control of the length and transverse cross-sectional area of the cavities 2 being formed in the film solution 6 as well as the diameter of open mouths 7 defined by the necks 4.
  • the relative humidity of the gaseous medium of the intermediate gas flow is significantly higher than the relative humidity of the gaseous medium of the initial gas flow, while the velocity of the gaseous medium of the intermediate gas flow over the top surface 8 of the film solution 6 is considerably slower than the velocity of the gaseous medium of the initial gas flow over the top surface 8 of the film solution 6.
  • the duration of the intermediate gas flow depends on the length, diameter and the shape of the cavities 2 to be formed.
  • the rate of solvent evaporation is controlled so that the level of solvent in the polymer/solvent solution of the film solution is such as to maintain the glass transition temperature of the film solution below the temperature of the film solution 6 in order to facilitate the formation of the cavities 2 therein when the film solution 6 is being subjected to the intermediate gas flow.
  • the final gas flow is commenced when the cavities 2 formed in the film solution 6 during the intermediate gas flow are of a desired predefined length in order to produce the polymer film 1 with the cavities 2 of the desired shape and size.
  • the relative humidity and the velocity of the gaseous medium of the final gas flow over the top surface 8 of the film solution 6 is set for evaporating the water of the water droplets in the cavities 2 formed in the film solution 6.
  • the relative humidity and the velocity of the final gas flow is also set so that when the water of the water droplets has been evaporated to an extent that the water droplets no longer have any influence in determining the shape of the cavities 2, the level of solvent remaining in the polymer/solvent solution of the film solution 6 adjacent the cavities 2 is sufficient to maintain the glass transition temperature of the polymer/solvent solution adjacent the cavities 2 below the temperature of the film solution 6. This thereby permits local polymer flow in the polymer/solvent solution in the vicinity of the cavities 2 for determining the final shape of the cavities 2.
  • this local polymer flow results in the formation of flat bottomed cavities 2, rather than cavities with a concave base when viewed through the open mouths 7 thereof.
  • the relative humidity of the gaseous medium of the final gas flow is considerably less than the relative humidity of the gaseous medium of the intermediate gas flow, and is in fact substantially similar to the relative humidity of the gaseous medium of the initial gas flow.
  • the velocity of the gaseous medium of the final gas flow over the top surface 8 of the film solution 6 is, in general, relatively slow in order to adequately control the respective rates of evaporation of the water and the solvent.
  • the apparatus 20 comprises a support platform 22 supported on ground engaging legs 24, and defining a planar horizontal upwardly facing top surface 25.
  • a housing 26 supported on the top surface 25 of the support platform 22 comprises a pair of spaced apart elongated longitudinally extending side walls 28 which are joined by a top wall 29.
  • the side walls 28 and the top wall 29 define with the top surface 25 of the support platform 22 a chamber 30 in the form of an elongated tunnel, within which the film solution 6 on the substrate 5 is located during forming of the cavities 2 therein.
  • the chamber 30 extends from an upstream end 31 to a downstream end 32.
  • the upstream end 31 is closed by an upstream end wall 33, within which an input port 34 is located for accommodating the nitrogen gas with entrained water vapour therethrough into the chamber 30 for producing the initial, intermediate and final gas flows through the chamber 30 to which the film solution 6 on the substrate 5 is subjected during forming of the cavities 2 therein.
  • the downstream end 32 of the chamber 30 is open for accommodating the gas flows from the chamber 30.
  • the balance 35 facilitates weighing of the film solution 6 during the initial, intermediate and final gas flows.
  • the substrate 5 defines a smooth planar horizontal upwardly facing top surface 38 for supporting the film solution 6 thereon.
  • a dosing port 39 formed in the top wall 29 of the housing 26 at a location above the substrate 5 is provided for drop-casting a predefined volume of the polymer/solvent solution onto the top surface 38 of the substrate 5 using a suitable micro-pipette (not shown) to form the film solution 6.
  • Nitrogen gas to produce the initial, intermediate and final gas flows is derived from a nitrogen gas supply 40, and is fed through a first flow control valve 41 to a supply pipe 42, and in turn to a first Y-piece connector 43.
  • a first pipeline 44 is coupled to the supply pipe 42 by the first Y-piece connector 43, and feeds into the inlet port 34 of the housing 26 through a second Y-piece connector 45 for delivering nitrogen gas from the supply pipe 42 into the chamber 30.
  • a second pipeline 46 which is also coupled to the supply pipe 42 through the first Y-piece connector 43 delivers nitrogen gas from the supply pipe 42 into a Dreschel flask 47 wherein water vapour is entrained in the nitrogen gas supplied from the supply pipe 42.
  • a third pipeline 48 couples the Dreschel flask 47 with the first pipeline 44 through the second Y-piece connector 45 for delivering nitrogen gas with water vapour entrained therein from the Dreschel flask 47 for varying the relative humidity of the nitrogen gas being delivered through the first pipeline 44 into the chamber 30.
  • the Dreschel flask 47 is supported on an electrically powered heater 50 which heats water in the Dreschel flask 47, and maintains the water therein at a suitable temperature to produce a sufficient level of water vapour entrained in the nitrogen gas from the second pipeline 46, so that the relative humidity of the nitrogen gas from the Dreschel flask 47 through the third pipeline 48 is approximately 100%.
  • the water in the Dreschel flask 47 is de-ionised and filtered.
  • First and second manually operated isolating valves 52 and 53 are located in the respective first and second pipelines 44 and 46 for selectively isolating the first and second pipelines 44 and 46 from the supply pipe 42, and also for varying the flow rate of the nitrogen gas through the first and second pipelines 44 and 46.
  • a second flow control valve 55 located in the first pipeline 44 between the first Y-piece connector 43 and the second Y-piece connector 45 is provided for varying and controlling the flow of nitrogen gas through the first pipeline 44 between the first and second Y-piece connectors 43 and 45 for in turn varying the relative humidity of the nitrogen gas flowing through the first pipeline 44 between the second Y-piece connector 45 and the inlet port 34 for in turn varying the relative humidity of the nitrogen gas flowing through the chamber 30.
  • the first flow control valve 41 facilitates varying the flow rate of nitrogen gas flowing through the chamber 30 for in turn varying the rate of evaporation of the solvent from the film solution 6.
  • the second flow control valve 55 facilitates varying the ratio of nitrogen gas flowing directly from the supply pipe 42 to the chamber 30 to nitrogen gas flowing through the Dreschel flask 47 to the chamber 30, for in turn varying the relative humidity of the nitrogen gas flowing through the chamber 30, for varying the rate of growth of the water droplets on the top surface 8 of the film solution 6 on the substrate 5.
  • a first flow rate monitor 56 is located on the first pipeline 44 between the first Y-piece connector 43 and the second Y-piece connector 45 for monitoring the flow rate of nitrogen gas through the first pipeline 44 between the first and second Y-piece connector 43 and 45.
  • a second flow rate monitor 57 is located in the third pipeline 48 for monitoring the flow rate of nitrogen gas with entrained water vapour flowing through the third pipeline 48.
  • a third flow rate monitor 58 is located in the first pipeline 44 between the second Y-piece connector 45 and the inlet port 34 of the housing 26 for monitoring the flow rate of nitrogen gas with entrained water vapour being delivered into the chamber 30.
  • Flow rates of nitrogen gas read by the first, second and third flow rate monitors 56, 57 and 58, respectively, are displayed on respective flow rate indicators 59 of the first, second and third flow rate monitors 56 to 58.
  • a probe 60 of a hygrometer 61 which also includes a temperature sensor 62, extends from the hygrometer 61 into the chamber 30 and terminates at a location adjacent the substrate 5.
  • the probe 60 monitors the relative humidity of the nitrogen gas with the water vapour entrained therein as it passes the film solution 6.
  • the temperature sensor 62 in the probe 60 monitors the temperature of the nitrogen gas with the entrained water vapour as it passes the film solution 6.
  • the relative humidity of the nitrogen gas flowing through the chamber 30 and the temperature thereof are displayed on a screen 63 of the hygrometer 61.
  • a separate temperature sensor located adjacent the top surface 8 of the film solution 6 monitors the temperature of the top surface 8 of the film solution 6.
  • the temperature of the top surface 8 monitored by the separate temperature sensor (not shown) is displayed on a separate screen (also not shown).
  • the first and second flow control valves 41 and 55 in this embodiment of the invention are manually operated for controlling the flow rate and the relative humidity of the nitrogen gas flowing through the chamber 30 by an operator in response to the values of the flow rates, the relative humidity and the temperature displayed by the first, second and third flow rate monitors 56 to 58, and the hygrometer 61 , respectively.
  • a microprocessor or a programmable logic controller may be provided coupled to the hygrometer 61 , the temperature sensor 62 and the first, second and third flow rate monitors 56 to 58 which would produce appropriate signals to be read by the microprocessor or the programmable logic controller.
  • the microprocessor or programmable logic controller would then control the operation of the first and second flow control valves 41 and 55 via suitable servomotors in response to the signals from the first, second and third flow rate monitors 56 to 58, the temperature sensor 62 and the hygrometer 61 for in turn controlling the flow rate and the relative humidity of the nitrogen gas flowing through the chamber 30.
  • the apparatus 20 With the apparatus 20 set up as described, and with the substrate 5 placed on the support platform 22 and the housing 26 also placed on the support platform 22 to form the chamber 30 with the substrate 25 located within the chamber 30 towards the downstream end 32 thereof and beneath the dosing port 39, the apparatus 20 is ready for use.
  • the first flow control valve 41 is set to produce the initial gas flow through the chamber 30 at a flow rate of approximately 5 litres of nitrogen gas and entrained water vapour per minute.
  • the second flow control valve 55 in conjunction with the second isolating valve 53 are set in order to produce a relatively dry initial gas flow of nitrogen of relative humidity, which is maintained at approximately 3%, through the chamber 30.
  • an appropriate volume, which in this embodiment of the invention is 60 micro-litres of the polymer/solvent solution is drop-cast through the dosing port 39 in the housing 26 onto the top surface 38 of the substrate 5 to form the film solution 6.
  • the volume of polymer/solvent solution which is drop-cast onto the substrate 5 may be of any suitable volume, and will be dependent on the desired product output. Drop-casting of the polymer/solvent solution is carried out using a suitable micro-pipette (not shown).
  • the depth t to which the film solution 6 of polymer/solvent solution settles on the top surface 38 of the substrate 5 depends on the polymer and solvent of the polymer/solvent solution and the proportions thereof in the solution, as well as other parameters such as surface tension, the smoothness of the top surface 38 of the substrate 5, the temperature of the polymer/solvent solution and the temperature and pressure within the chamber 30.
  • the polymer is a, ⁇ -Dicarboxy Terminated Polystyrene of number average molecular weight of 93,800gms/mol, and the solvent is chloroform.
  • the starting proportion of the polymer to the solvent by mass is 3.5% polymer to 96.5% solvent.
  • the method is carried out at room temperature, which is approximately 21 °C, and pressure, and on being drop-cast onto the top surface 38 of the substrate 5, the polymer/solvent solution is at room temperature.
  • the temperature and pressure within the chamber 30 during the carrying out of the method is substantially room temperature and pressure. Under these conditions the depth t to which the film solution 6 settles on the top surface 38 of the substrate 5 in a central area of the film solution 6 where the depth t is substantially constant and is in the order of 550 microns.
  • the top surface 8 of the polymer/solvent film solution 6 forms an upwardly facing exposed gas/film interface surface over which the initial, intermediate and final gas flows pass, and forms the top surface 3 of the polymer film 1 when the cavities 2 have been formed therein.
  • the level of solvent in the polymer/solvent solution remains at a level which is sufficient for maintaining the glass transition temperature of the polymer/solvent solution below the temperature of the film solution 6 during the initial and intermediate gas flows, and also during the final gas flow until local polymer flow in the film solution adjacent the cavities has been completed in order to form the cavities 2 of the desired shape.
  • the starting proportions of the polymer and solvent in the polymer/solvent solution in order to maintain the glass transition temperature of the polymer/solvent solution below the temperature of the film solution until local polymer flow in the film solution adjacent the cavities has been completed will depend on the types of polymers and solvents which are selected to form the polymer/solvent solution.
  • the maximum feasible concentration as a percentage of mass of the polymer of the polymer/solvent solution for any polymer/solvent solution is achieved when the vapour pressure of the polymer solution induces exactly enough evaporative cooling so that the polymer surface is reduced to the dew point temperature of the system. With any further increase in polymer concentration, the dew point temperature will not be reached, and so no condensation or minimum condensation of water on the surface of the polymer/solvent solution will occur.
  • the flow rate of the initial gas flow of 5 litres per minute through the chamber 30 equates to a velocity of the gas of the initial gas flow over the top surface 8 of the film solution of approximately 0.29 metres per second.
  • the film solution 6 is subjected to the initial gas flow for a first time period of approximately 45 seconds, see Fig. 7, in order to produce a polymer concentration gradient extending from the top surface 8 into the film solution 6 with the polymer concentration decreasing from the top surface 8 in a direction into the film solution 6. Additionally, by providing the initial gas flow to flow over the top surface 8 of the film solution 6 at a velocity of 0.29 metres per second and at a relative humidity of approximately 3%, the evaporation of the solvent from the film solution 6 reduces the surface temperature of the top surface 8 of the film solution 6 to a temperature of the order of 0°C to 5°C at the end of the first period of 45 seconds.
  • This temperature range is well below the dew point temperature of the intermediate gas flow, and on the film solution being subjected to the intermediate gas flow, water droplets immediately commence to form on the top surface 8 of the film solution 6.
  • condensing of water vapour from the initial gas flow onto the top surface 8 of the film solution 6 is minimal, and in general, does not occur.
  • the initial gas flow can be terminated after approximately 45 seconds, and the intermediate gas flow can be immediately commenced, see Fig. 7.
  • sufficient solvent has been evaporated from the film solution 6 to establish the polymer concentration gradient down through the film solution 6 from the top surface 8 thereof whereby the concentration of the polymer decreases downwardly into the film solution 6 from the top surface 8.
  • the polymer concentration gradient controls the rate at which the water droplets which form on the top surface of the film solution 6 grow downwardly through the top surface 8 into the film solution 6 to form the cavities 2.
  • the relative humidity of the gas flow is immediately increased to reach a target value of approximately 85% by appropriately setting the second flow control valve 55 to produce the intermediate gas flow, see Fig. 7.
  • the manually operated isolating valves 52 and 53 may also be used for controlling the relative humidity of the initial, the intermediate and the final gas flows.
  • the first flow control valve 41 is operated to reduce the flow rate of the intermediate gas flow to a steady state flow rate of approximately 1.0 litres per minute.
  • the flow rate of 1.0 litres per minute equates to a velocity of the gas of the intermediate gas flow over the top surface 8 of the film solution 6 of approximately 0.06 metres per second.
  • the target relative humidity is reached after approximately 110 seconds after the commencement of the intermediate gas flow, and the intermediate gas flow is continued for a further 10 seconds thus, giving a total second time period for the intermediate gas flow of approximately 120 seconds, see Fig. 7.
  • the intermediate gas flow is terminated, and the final gas flow is commenced.
  • the average relative humidity of the gas is approximately 69%. It has been found that by maintaining the intermediate gas flow for the second time period of 120 seconds under the conditions set out above, cavities 2 of a predefined size and shape are formed, which result in the cavities 2 of the polymer film 1a of Fig. 3 being formed after the film solution 6 has been subjected to the final gas flow.
  • the first flow control valve 41 and the second flow control valve 55 are operated to reduce the relative humidity of the gas flow to approximately 11 % in order to establish the final gas flow to which the film solution 6 is now subjected.
  • the flow rate of the gas is maintained substantially similar to the flow rate during the intermediate gas flow so that the velocity of the final gas flow over the top surface 8 of the film solution 6 is maintained at approximately 0.06 meters per second.
  • the relative humidity of the final gas flow drops off relatively rapidly over a period of 60 seconds to approximately 1 %.
  • the final gas flow may also be controlled to permit local polymer flow adjacent the side walls of the cavities 2, which generally results in a decrease in the diameter of the cavities 2, and it is possible to control the diameter of the cavities to begin to approach the diameter of the respective open mouths 7 defined by the necks 4 of the cavities 2.
  • This shaping of the side walls of the cavities 2 may also result in an increase in the spacing between adjacent cavities 2.
  • the final gas flow is continued until substantially all of the solvent has been evaporated from the film solution 6 to produce the polymer film 1 as an entangled polymer film, in which the polymer can no longer flow.
  • the relative humidity of the final gas flow is allowed to fall off to a value of approximately 4%, see Fig. 7.
  • the total time during which the film solution should be subjected to the intermediate and final gas flows is approximately eight minutes.
  • the duration during which the film solution 6 is subjected to the final gas flow will be relatively shorter than cases where the film solution is subjected to the intermediate gas flow for relatively shorter periods.
  • the total time period during which the film solution is subjected to the intermediate and final gas flows may be greater or less than eight minutes, depending on the size of the cavities required, and indeed, it is envisaged that a shorter time period than eight minutes may be sufficient for the formation of cavities of relatively small size.
  • the relative humidity and the flow rate of the initial gas flow are set so that the polymer gradient of the polymer in the film solution 6 is appropriately set in order to support condensing water from the intermediate gas flow as the water droplets are formed on the top surface 8 of the film solution 6, while at the same time the viscosity of the film solution 6 adjacent the top surface 8 thereof is such as to permit penetration into the film solution 6 through the top surface 8 thereof of the water droplets in order to form the cavities 2.
  • the rate of evaporation of the solvent from the film solution 6 during the initial gas flow is such as to reduce the surface temperature of the top surface 8 of the film solution 6 to be well below the dew point temperature of the intermediate gas flow.
  • the flow rate and the relative humidity of the intermediate gas flow is such that water droplets condense out of the intermediate gas flow onto the top surface 8 of the film solution 6 in the form of a hexagonally close-packed array.
  • solvent continues to evaporate from the film solution 6, although at a reduced evaporation rate due to the slower velocity of the intermediate gas flow over the top surface 8 of the film solution 6.
  • This reduction in the evaporation rate of the solvent during the intermediate gas flow results in a gradual increase in the temperature of the top surface 8 of the film solution 6, although it has been found that this gradual increase in the temperature of the top surface 8 of the film solution 6 does not to any great extent hinder the formation of the water droplets in the hexagonally close-packed array of the film solution 6.
  • the polymer gradient progressively increases downwardly into the film solution 6 from the top surface 8 thereof. This, thus, controls the growth of the water droplets downwardly from the top surface 8 into the film solution 6.
  • the relative humidity and the flow rate of the intermediate gas flow is also set to control the progression of the polymer concentration gradient downwardly through the film solution 6 during the period during which the film solution 6 is subjected to the intermediate gas flow.
  • the duration of the intermediate gas flow will vary depending on the size and shape of the cavities required. However, in order to produce the polymer film 1 with the cavities 2 with a flat base, it is important that the second time period during which the film solution 6 is subjected to the intermediate gas flow is terminated prior to evaporation of all of the solvent from the film solution 6, so that sufficient solvent remains in the film solution 6 during the final gas flow when the water droplets have been evaporated from the cavities 2 to the extent that the remaining water in the cavities 2 has little or no influence on the formation of the cavities 2, to maintain the glass transition temperature of the polymer/solvent solution below the temperature of the film solution 6, in order to permit local polymer flow adjacent the bases 10 of the cavities 2 so that the cavities 2 are produced with flat bases 10.
  • the relative humidity and the flow rate of the final gas flow and the duration of the final gas flow will also vary depending on the size and shape of the cavities required. However, when it is desired to form the polymer film 1 with cavities 2 with flat bases 10, it is important that the relative humidity and flow rate of the final gas flow should be set so that water of the droplets in the cavities 2 is evaporated to the extent that the amount of water remaining in the cavities 2 no longer has an over-riding influence on the size and shape of the cavities while there is still sufficient solvent remaining in the film solution 6 to permit local polymer flow adjacent the cavities, and in particular, adjacent the base 10 of the cavities 2.
  • the local polymer flow adjacent the base of the cavities 2 results in the formation of the cavities 2 with flat bases 10.
  • This requirement may also require adjustment of the relative humidities and flow rates of the initial and intermediate gas flows, to ensure that when the cavities 2 are of the predefined size, depth and diameter at the end of the intermediate flow to produce the cavities 2 in the polymer film 1 of the desired size and shape, sufficient solvent remains in the film solution 6 so that during the period while the film solution 6 is being subjected to the final gas flow, sufficient solvent remains in the film solution after the water of the water droplets has been evaporated from the cavities 2 to the extent that the water in the cavities no longer has an over-riding influence on the size and shape of the cavities to maintain the glass transition temperature of the polymer/solvent solution below the temperature of the film solution 6 in order to facilitate local polymer flow adjacent the relevant portions of the cavities 2 which are to be shaped in order to produce cavities 2 in the polymer film 1 of the desired size and shape.
  • the relative humidity of the initial gas flow will lie in the range of 0% to 45%, while the flow rate will in general lie in the range of 0.5 litres per minute to 20 litres per minute in order to produce a velocity of the initial gas flow over the top surface 8 of the film solution 6 in the range of 0.03 metres per second to 1.14 metres per second.
  • the relative humidity of the intermediate gas flow will lie in the range of 10% to 100%, depending on the size and dimensions of the cavities 2 to be formed in the polymer film 1.
  • the flow rate of the intermediate gas flow will in general lie in the range of zero litres per minute to 7 litres per minute in order to produce a velocity of the intermediate gas flow over the top surface 8 of the film solution 6 in the range of zero metres per second to 0.4 metres per second.
  • the relative humidity of the final gas flow will lie in the range of 0% to 50%, while the flow rate will in general lie in the range of zero litres per minute to 7 litres per minute in order to produce a velocity of the final gas flow over the top surface 8 of the film solution 6 in the range of zero metres per second to 0.4 metres per second.
  • the size and shape of the cavities 2 can be altered. For example, flat based cavities, spherical cavities, bulbous cavities with narrow necks 4 and conical flask-like cavities can be formed in the film solution 6.
  • Flat base cavities are achieved by ensuring that at the stage in the final gas flow when the water has been evaporated to a stage when the remaining water in the cavities no longer has an over-riding influence on the shape and size of the cavities, sufficient solvent remains in the film solution 6 to maintain the glass transition temperature of the polymer/solvent solution below the temperature of the film solution. This, thus, permits local polymer flow adjacent the cavities in order to determine the final shape of the cavities 2 in the polymer film 1.
  • the relative humidity of the initial gas flow should be below or close to the critical humidity level required to initiate water condensation onto the top surface 8 of the film solution 6 as the solvent is evaporating.
  • critical humidity level is used in this specification to mean the borderline humidity below which condensation of water onto the surface 8 of the film solution is not favoured.
  • the initial gas flow is chosen to set the minimum feasible surface temperature of the top surface 8 of the film solution by controlling the rate of evaporation while minimising water
  • the initial gas flow for a given solution dictates the temperature and concentration gradient within the film solution 6.
  • the flow rate and the relative humidity of the intermediate gas flow is set in conjunction with the surface temperature induced from the initial gas flow to allow control of the vapour-liquid equilibrium of water adjacent the top surface 8 of the film solution 6, and hence, the drive to condense water vapour from the intermediate gas flow to form water droplets on the gas/film interface 8 of the film solution 6 during the intermediate gas flow. This drive to condense the water vapour from the
  • intermediate gas flow is modified to induce the required amount of droplet growth on the top surface 8 of the film solution 6, and in turn the droplet growth into the film solution to form the cavities.
  • the intermediate gas flow also controls the progression of the solvent evaporation and the polymer concentration gradient in the film solution 6, thereby allowing and controlling the growth rate of the droplets into the solution.
  • the final gas flow By providing the final gas flow to be of low humidity results in a change of the vapour-liquid equilibrium of the droplets, and thereby ensures their rapid evaporation before complete evaporation of the solvent from the film solution 6.
  • the vapour-liquid equilibrium adjacent the droplet interface with the gas of the final gas flow favours the evaporation of water droplets from the cavities, however, due to the presence of solvent in the film solution 6, the film solution 6 is sufficiently viscous to allow local polymer flow adjacent the base of the cavities to form flat bottomed cavities.
  • Shallow cavities can also be formed by significantly decreasing the relative humidity of the intermediate gas flow until it is just above the critical humidity level at which condensation would form on the top surface 8 of the film solution 6 and terminating the intermediate gas flow when the cavities 2 have been formed to a predefined depth, which would result in the cavities 2 in the polymer film 1 being formed to the desired shallow depth.
  • the size and depth of the cavities are determined by the relative humidity of the intermediate gas flow and the duration during which the film solution 6 is subjected to the second gas flow.
  • Table 1 sets out the conditions and durations of the initial, intermediate and final gas flows used in the formation of the polymer films 1 b to 1 d of Figs. 4 to 6.
  • the polymer and solvent and the starting proportions thereof of the film solutions are similar to those of the example of the polymer film described above, and the polymer/solvent film solutions of Examples 1 to 3 are formed on the substrate 5 to a similar depth t of 550 microns as that of the film solution 6.
  • the graphs of Figs. 8 to 10 show the relative humidity of the initial, intermediate and final gas flows during the respective initial, intermediate and final gas flows plotted against time during the formation of the polymer films 1 b to 1d of Figs. 4 to 6, respectively.
  • the depth of the cavities 2 in the polymer film 1 b is less than the depth of the cavities 2 in the polymer film 1a.
  • the average relative humidity of the intermediate gas flow at 65.2% of Example 1 was less than the average relative humidity of the intermediate gas flow which produced the polymer film 1a of Fig. 3
  • the duration of the intermediate gas flow was shorter at approximately 90 seconds than the duration of the intermediate gas flow of 120 seconds which produced the polymer film 1a of Fig. 3.
  • a further comparison of the polymer films 1a, 1 b and 1 c of Figs. 3, 4 and 5 shows that the depth of the cavities 2 in the polymer film 1 c is less than the depth of the cavities in the polymer film 1 b which in turn is less than the depth of the cavities 2 of the polymer film 1 a.
  • the further reduction in the depth of the cavities 2 of the polymer film 1c of Fig. 5 can be explained by virtue of the fact that the average relative humidity of the intermediate gas flow at 56.2% of Example 2 which produced the polymer film 1c of Fig. 5 was less than the relative humidity of 65.2% and 69% of the intermediate gas flows which produced the polymer films 1 b and 1 a, of Figs. 4 and 3, respectively.
  • the duration of the intermediate gas flow of Example 2 which produced the polymer film 1c of Fig. 5 at 60 seconds approximately was less than the 90 second duration of the intermediate gas flow which produced the polymer film 1 b of Fig. 4 and the 120 second intermediate gas flow which produced the polymer film 1 a of Fig. 3.
  • the lesser depth of the cavities 2 of the polymer film 1 d of Figs. 6a and b can be explained by the fact that the average relative humidity of the intermediate gas flow at 39.3% of Example 3 which produced the polymer film 1d is less than the average relative humidity of the intermediate gas flow of 56.2% of Example 2 which produced the polymer film 1c of Fig. 5 which in turn is less than the average relative humidity of the intermediate gas flow at 65.2 of Example 1 which produced the polymer film 1 b of Fig. 4, which in turn is less than the average relative humidity of the
  • the duration of the intermediate gas flow of Example 3 which produced the polymer film 1d of Figs. 6a and b at 30 seconds is less than the intermediate gas flow at 60 seconds which produced the polymer film 1c of Fig. 5 which in turn is less than the 90 second intermediate gas flow which produce the polymer film 1 b of Fig.
  • the cavities formed in the polymer films 1a to 1d each have a substantially flat base, which results from local flow of the polymer in the film solution 6, while there is still sufficient solvent remaining in the film solution 6 after the water of the water droplets in the cavities 2 has been evaporated to an extent that the water in the cavities no longer has an over-riding influence on the shape and size of the cavities.
  • the cavities 2 extend downwardly into the polymer film from the neck 4 which is of smaller diameter to the diameter of the cavities beneath the neck.
  • This enlargement of the diameter of the cavities beneath the neck is believed may also result from local flow of the polymer in the film solution 6 while the amount of solvent in the film solution 6 is sufficient to accommodate local polymer flow adjacent the cavities 2 after the water of the water droplets in the cavities 2 has been evaporated to an extent that the remaining water in the cavities 2 no longer influences the size and shape of the cavities. It has also been found that this local polymer flow may increase the spacing between adjacent cavities. It can also be seen from Figs.
  • a film solution identical to the film solution 6 of similar depth and comprising a similar polymer/solvent solution was placed on the substrate 5 in the chamber 30 of the apparatus 20 of Fig. 1.
  • the film solution was subjected to an initial gas flow of 5 litres per minute of dry nitrogen for a first time period of 45 seconds.
  • the film solution was subjected to an intermediate gas flow at a rate of 1 litre per minute of humid nitrogen until all the solvent was evaporated.
  • the film solution was not subjected to a final gas flow, rather, the intermediate gas flow was continued until all solvent had been evaporated from the film solution.
  • the graph of Fig. 12 may be used to indicate where the second time period of the intermediate gas flow would end and the third time period of the final gas flow could commence as will be described below.
  • Fig. 11 illustrates a plot of the glass transition temperature in degrees centigrade, which is plotted on the vertical Y-axis against the concentration of solvent as a percentage of the mass of the polymer/solvent solution, which is plotted on the horizontal Y-axis. This plot has been prepared from the Beuche equation.
  • Fig. 12 illustrates two graphs, namely Graph A, which illustrates a plot of the concentration of polymer as a percentage of the mass of the polymer/solvent solution plotted against time as the film solution is being subjected to the first and second gas flows described above.
  • the concentration of polymer as a percentage of the mass of the polymer/solvent solution is plotted on the left-hand vertical Y-axis, and time in seconds is plotted on the horizontal X-axis.
  • Graph B of Fig. 12 is a plot of the glass transition temperature in degrees centigrade plotted against time as the film solution is being subjected to the first and second gas flows.
  • the glass transition temperature in degrees centigrade is plotted on the right-hand vertical Y-axis, and time, as discussed above, is plotted on the horizontal X-axis.
  • the plot of the glass transition temperature against time has been derived empirically from the Beuche equation and the graph of Fig. 11.
  • the film solution was subjected to the first and second gas flows at room temperature, namely, approximately 21 °C, and room pressure, and thus, the film solution would have been maintained at a temperature of approximately 21 °C.
  • room temperature namely, approximately 21 °C
  • room pressure room pressure
  • the glass transition temperature of the polymer/solvent solution remained below 0°C at -27°C, which is well below the room temperature of 21 °C.
  • the evaporation of the solvent from the polymer/solvent solution commences to accelerate at approximately 100 seconds into the experiment, and this, thus, leads to an acceleration of the increase in the glass transition temperature of the polymer/solvent solution.
  • the second time period during which the polymer/solvent solution is subjected to the intermediate gas flow should terminate prior to the time at which the concentration of the polymer in the film solution commences to increase more rapidly.
  • the second time period should terminate between 30 and 60 seconds after the commencement thereof, or in other words, between 80 seconds and 100 seconds from the commencement of the experiment, and at that stage, the polymer/solvent solution should be subjected to the third gas flow.
  • Figs. 13 and 14 illustrate three further examples of polymer film 1(e), 1(f) and 1 (g) prepared in three further examples of the method according to the invention, namely, Examples 4 and 5.
  • the conditions under which Examples 4 and 5 have been carried out are set out in Table 2.
  • Graphs of the relative humidity of the gas flows during the initial, intermediate and final gas flows to which the polymer films 1(e) and 1 (f) of Figs. 13 and 14 were subjected in Examples 4 and 5 are illustrated in Figs. 15 and 16, respectively.
  • the polymer/solvent solution of the film solution of Examples 4 and 5 are similar to the polymer/solvent solution of the film solution 6 described above, and the film solution was formed to a depth of 550 microns on the substrate 5, which in turn was placed in the chamber 30 of the apparatus 20.
  • Table 2 The polymer/solvent solution of the film solution of Examples 4 and 5 are similar to the polymer/solvent solution of the film solution 6 described above, and the film solution was formed to a depth of 550 microns on the substrate 5, which in turn was placed in the chamber 30 of the apparatus 20. Table 2
  • Example 4 the first time period during which the polymer/solvent solution was subjected to the first gas flow was approximately 50 seconds, see Fig. 15.
  • Example 4 the relative humidity of the intermediate gas flow was raised rapidly to approximately 82%.
  • the third gas flow commenced in Example 4 at 160 seconds approximately from the commencement of the initial gas flow.
  • Example 5 the polymer/solvent solution was subjected to the initial gas flow for approximately 60 seconds, and to the intermediate gas flow for approximately 140 seconds, see Fig. 16.
  • the relative humidity was raised rapidly to approximately 80% and subsequently to 84%.
  • the third gas flow commenced at approximately 200 seconds from the commencement of the initial gas flow.
  • the cavities 2 which have been formed in the polymer film 1f are of circular transverse cross- section in plan view with a relatively flat base 10 but rather bulbous above the base 10 and below the neck 4.
  • polymer/solvent solution has been described as comprising specific constituents of specific starting proportions, it will be readily apparent to those skilled in the art that the polymer/solvent solution may be provided with the constituents in other suitable starting proportions. Needless to say, the polymer solvent solution may comprise constituents other than those described, and/or may comprise additional constituents as well as those described.
  • the film solution instead of being formed on the top surface of a substrate which is horizontally oriented, the film solution may be formed on an inclined surface of a substrate.
  • the surface of the substrate may be a vertical surface, and in other cases, it is envisaged that the film solution may be formed on an underneath surface of a horizontal or inclined substrate.
  • the film solution may be prepared from any other suitable polymer and/or solvent, and the starting proportions of the polymer and the solvent of the solution will be largely determined by the types of polymer and the types of solvent.
  • any other suitable gaseous medium may be used, for example, air, and the gaseous medium may be entrained with any suitable liquid besides water.
  • first, second and third environments which are provided by initial, intermediate and final gas flows
  • other forms of first, second and third environments may be provided.
  • the film solution may be subjected to static first, second and third environments.
  • the three environments could be established in a three-stage process, where the film solution on the substrate could be moved sequentially through the three stages of the process. Indeed, in each stage of such a three-stage process, the environments could be static or could be provided as gas flows.
  • the polymer films formed according to the invention will have many uses, for example, in drug delivery devices, such as micro-needle and other micro devices for delivering drugs to a subject over relatively lengthy treatment periods, for example, over seven to fourteen days, and indeed longer.
  • the polymer films are also suitable for use in photonic applications, whereby the cavities may be used as time delay elements, filter elements and for other photonic applications.
  • the polymer films produced according to the invention are relatively lightweight, strong and mechanically robust structures with tuneable strength such as crush strength, yield points and the like.
  • the polymer films according to the invention may be used as cell scaffolding to grow cells, such as skin and tissue cells. It is envisaged that nutrients to grow cells may be included in the cavities formed in the polymer film which would enhance cell growth.
  • the method according to the invention may be carried out at any suitable temperature or pressure, other than room temperature and pressure as has been described. Indeed, it is envisaged that the method could be carried out in a completely enclosed environment whereby as well as controlling the relative humidity of the first, second and third environments, the temperatures and pressures of the first, second and third environments could also be controlled. In which case, the method could be carried out as a three-stage process with the film solution on the substrate being moved sequentially through the three stages of the process.

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Abstract

L'invention concerne un procédé de production d'un réseau de cavités (2) dans un film polymère (1), qui comprend les étapes consistant à : préparer une solution de polymère/solvant et couler par gravité un film mince (6) de la solution sur un substrat ; soumettre la solution (6) de film à trois écoulements gazeux. On fait passer un écoulement gazeux initial présentant une humidité relativement faible sur la solution (6) de film pour évaporer le solvant de la solution (6) de polymère/solvant, afin de réduire la température de surface de la solution (6) de film à une valeur inférieure à la température de point de rosée de l'écoulement gazeux suivant, à savoir un écoulement gazeux intermédiaire. L'écoulement gazeux intermédiaire, qui présente une humidité relativement élevée, forme sur la surface de la solution (6) de film des gouttelettes qui croissent dans la solution de film de manière à y former des cavités (2). Un écoulement gazeux final fait évaporer les gouttelettes des cavités formées (6) ainsi que le solvant de la solution (6) de film, mais permet de maintenir à un certain niveau le solvant dans la solution (6) de film quand les gouttelettes ont été évaporées suffisamment pour ne plus avoir d'influence sur la formation des cavités (2), de sorte que la température de transition vitreuse de la solution de polymère/film adjacente aux cavités (2), inférieure à la température de la solution (6) de film, permet à l'écoulement local du polymère adjacent aux cavités (2) de déterminer la forme finale des cavités (2).
PCT/IE2010/000058 2009-10-14 2010-10-14 Procédé de production d'un film polymère contenant un réseau de cavités Ceased WO2011045777A1 (fr)

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Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020143073A1 (en) 2000-11-17 2002-10-03 Peng Jiang Polymers having ordered, monodisperse pores and their corresponding ordered, monodisperse colloids
US20030106487A1 (en) 2001-12-10 2003-06-12 Wen-Chiang Huang Photonic crystals and method for producing same
US20030129311A1 (en) 2002-01-10 2003-07-10 Wen-Chiang Huang Method of producing quantum-dot powder and film via templating by a 2-d ordered array of air bubbles in a polymer
CN1511874A (zh) 2002-12-30 2004-07-14 中国科学院化学研究所 有序孔聚合物膜及其制备方法
US20040138323A1 (en) 2000-12-19 2004-07-15 Stenzel-Rosebaum Martina Heide Porous polymers
CN1676204A (zh) 2004-04-01 2005-10-05 中国科学院化学研究所 三维有序微米孔聚合物膜及其制备方法
WO2006112358A1 (fr) 2005-04-13 2006-10-26 National University Corporation Hokkaido University Traitement pour la production d’un materiau poreux de type nid d’abeille
WO2007086421A1 (fr) 2006-01-26 2007-08-02 National University Corporation Hokkaido University Article poreux de type en nid d’abeille utilisable en thérapie de régénération de tissus durs
DE102006036863A1 (de) * 2006-08-03 2008-02-14 Technische Universität Chemnitz Mechanisch stabile poröse Membran, Verfahren zu ihrer Herstellung und ihre Verwendung
WO2009069110A1 (fr) 2007-11-26 2009-06-04 The Provost, Fellows And Scholars Of The College Of The Holy And Undivided Trinity Of Queen Elizabeth, Near Dublin Procédé de production d'une matrice de pores de forme cylindrique dans un film de polymère et film de polymère produit selon ce procédé
US20100070026A1 (en) * 2008-09-12 2010-03-18 Fujifilm Corporation Stent with porous membrane and manufacturing method thereof

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020143073A1 (en) 2000-11-17 2002-10-03 Peng Jiang Polymers having ordered, monodisperse pores and their corresponding ordered, monodisperse colloids
US20040138323A1 (en) 2000-12-19 2004-07-15 Stenzel-Rosebaum Martina Heide Porous polymers
US20030106487A1 (en) 2001-12-10 2003-06-12 Wen-Chiang Huang Photonic crystals and method for producing same
US20030129311A1 (en) 2002-01-10 2003-07-10 Wen-Chiang Huang Method of producing quantum-dot powder and film via templating by a 2-d ordered array of air bubbles in a polymer
CN1511874A (zh) 2002-12-30 2004-07-14 中国科学院化学研究所 有序孔聚合物膜及其制备方法
CN1676204A (zh) 2004-04-01 2005-10-05 中国科学院化学研究所 三维有序微米孔聚合物膜及其制备方法
WO2006112358A1 (fr) 2005-04-13 2006-10-26 National University Corporation Hokkaido University Traitement pour la production d’un materiau poreux de type nid d’abeille
WO2007086421A1 (fr) 2006-01-26 2007-08-02 National University Corporation Hokkaido University Article poreux de type en nid d’abeille utilisable en thérapie de régénération de tissus durs
DE102006036863A1 (de) * 2006-08-03 2008-02-14 Technische Universität Chemnitz Mechanisch stabile poröse Membran, Verfahren zu ihrer Herstellung und ihre Verwendung
WO2009069110A1 (fr) 2007-11-26 2009-06-04 The Provost, Fellows And Scholars Of The College Of The Holy And Undivided Trinity Of Queen Elizabeth, Near Dublin Procédé de production d'une matrice de pores de forme cylindrique dans un film de polymère et film de polymère produit selon ce procédé
US20100070026A1 (en) * 2008-09-12 2010-03-18 Fujifilm Corporation Stent with porous membrane and manufacturing method thereof

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