TECHNOLOGICAL FIELD

The present invention relates to flexible films having micro- and/or nano- structures and to a technique for production of such films. The invention is specifically relevant for continuous/industrial productions of micro-structured films. BACKGROUND

Flexible polymeric films having micro-structured patterns are of high demand for various applications such as flexible electronics, displays, micro filtration, super- hydrophobic surfaces, IR photonic management surfaces, antifouling, self -cleaning films, blood testing, liquid gripping, anti-fog and/or anti-ice systems, polarizers, antennas and more. The conventional techniques for manufacturing of such films are relatively expensive and provide low production volume. This is due to the various types of specialty equipment needed for generating micrometric and/or nanometric patterns to desired specification.

Patterning of fine structures on polymeric films may be performed by methods such as lithography, laser abrasion, mechanical puncturing, breath figures, imprinting, printing, stamping and other techniques. Generally, these techniques may be slow and expensive for production, raising costs of the patterned films. For examples, breath figure techniques are relatively effective but provide difficulty in controlling of the formed structure. This is at least partly due to the need to control the relative humidity (RH) and temperature very strictly with strict timings. Other technique such as track etching are expensive and produces low pore density limiting applicability of such techniques. GENERAL DESCRIPTION

There is a need in the art for a novel manufacturing technique enabling production of patterned films having micro- and/or nano-scale patterns of selected characteristics. The technique of the present invention utilizes providing the film in contact with a liquid mixture comprising a mixture of one or more solvent materials selected for dissolving the film material and one or more non-solvent materials.

In this connection, a solvent material is referred herein to a material, e.g. chemical compound, that dissolves the material of the selected film, generally supporting high concentration of the dissolved material in common phase; a non-solvent material is referred to herein to materials that are generally inert to dissolving the material of the film and typically do not show significant dissolving effect when in contact with the film. In the context of this patent application, a "solvent" generally relates to a material capable of interaction with the film material and swelling it and does not necessarily imply 100% dissolution of the film material(s). Additionally, a "non-solvent" generally relates to material incapable of substantial interaction with the film material(s), and does not necessarily imply 0% dissolution.

The film may be polymeric film and may be applied on a substrate for protection and simplified handling. Moreover, in some preferred configurations of the present invention the substrate layer may be configured with at least one functional surface thereof, being in contact with the polymeric film to be patterned. Generally, the functional surface may be associated with a surface property of the substrate or coating thereon. In some preferred configurations, the functional property of the surface may be to apply a non-stick layer. This simplifies peeling of the film from the substrate after processing. Additionally, as described further below, the use of non-stick surface property (or coating) on the substrate may provide a through pores pattern where the pores' structures formed on the film penetrate through the full thickness of the film.

When the polymeric film is immersed in the liquid mixture, the solvent component of the mixture may act on the polymeric material of the film by swelling the film material thereby chaperoning the non-solvent into the film with it. After a selected time period (duration) of interaction with the liquid mixture, the film is dried, allowing the mixture to evaporate. Generally, the one or more solvent materials are selected as one or more materials having faster evaporation rates (e.g. having lower boiling point and/or high partial vapor pressure) with respect to the non-solvent material. This results in the solvent material(s) evaporation while leaving a certain amount of the one or more non- solvent materials in, or on, the film. This residue of the non-solvent material may typically be self-arranged in microscopic droplets allowing the film material to re-solidify providing pattern thereon.

The so-formed patterns may be superficial, on the surface of the film exposed to the liquid mixture, or it may form through pores penetrating through the full thickness of the film. This may be determined by thickness of the film, time of interaction with the liquid mixture, the composition of the liquid material, ambient conditions, as well as physical limitation and barriers.

More specifically, the polymeric film may be located on a substrate carrier to simplify handling and production. In this case, the substrate carrier may form a barrier for penetration of the pores through thickness of the film even for long periods of interaction with the solvent/non-solvent liquid mixture. The inventors of the present invention have found that in order to provide through pores in the polymeric film, while using a substrate carrier, a non-stick surface functionality (e.g. low surface energy layer) is preferred on the surface of the substrate in contact with the polymeric film. For example, a non-stick coating may be applied on the substrate between the substrate and the polymeric film. Such non-stick layer may be formed of e.g. Fluorinated polymer, ETFE, silicone (polysiloxanes), etc. typically used as a coating on the substrate material.

Generally, the thickness of the polymeric film may be selected in accordance with the film material of choice and the selected application. For example, the polymeric film may be used with the thickness between lOnm and 1mm, and preferably between lOOnm and lOOum. The roll to roll patterning technique, as described herein, is generally suitable for use with flexible and reliable films, e.g. capable of being rolled into rolls holding film length that may be above 30cm or above 100m and at times even between 3km to 24km long. This allows large scale and robust patterning of the polymeric film while maintaining low cost manufacturing. The pattern is in the form of self-assembled nano- and/or microscopic features of at least one surface of the polymeric film. The technique may also be utilized in a batch-type or semi-continuous process such as sheet-to-sheet or step-and-repeat. Depending on the film material and the desired pattern features, the solution mixture may include several solvents and non-solvents, in different ratios. Selection of the solvent and non-solvent materials also depends on solvability parameters with respect to the film, mixing properties of the solvent and non-solvent materials and evaporation properties. For typical polymeric film materials the solvent material may be selected from: Acetophenone, THF, DCM, Chloroform, CS2, DMF, DMSO, Pentyl acetate, Ethyl acetate, Cyclohexanone, 1 ,4-Dioxane, Xylene, Toluene, Benzene. The non-solvents can be selected from alcohols, including MeOH, EtOH, and higher alcohols, IPA, and others, H20, Oil of different types, glycerol and more.

It should be noted that the term polymeric film is used herein to indicate that, generally, the present technique is most suitable for patterning of such polymeric films. However, such film may be selected from various block co-polymers with hydrophobic and hydrophilic sides, Dendrimers to induce the phase separation, and common engineering polymers and even a common and low cost linear polymer can be used. A hydrophobic block co- polymer may also be used. For example, material of the film may be selected from: PET, PS, PMMA, all acrylic block co-polymers, PMMA-PnBA, PE, PP, Polyamide, Polyimide, PTFE, ETFE, PVC, PC, PES, ABS, PVA, PVAc, Cellulose acetate, cellulose nitrile, cellulose ether, PEEK, PVDF, Polyacrylonitrile, PDMS and copolymers of these materials thereof.

In addition to polymeric films, the technique may be applied to particle-based material/film containing nano- and/or micro-particles coated or non-coated with a high affiliation to certain solvents and low affiliation to other (second) solvents. The invention also covers a ternary system in which the use of at least three solvents allows for the formation of two types of patterns in the film. For example, this may include one set of holes in a certain range of sizes and a second matrix of holes in a second range of sizes. In an additional example, this may refer to one set of holes which completely transcend the full thickness of the film and a second set of 'blind' holes (grooves) which do not transcend the full thickness of the film.

Thus, according to a broad aspect, the present invention provides a method for use in manufacturing of patterned film, the method comprising:

providing a substrate layer film carrying a non-stick coating on at least one surface thereof; providing a polymeric film on said non-stick coating thereby providing polymeric film on substrate;

bringing the polymeric film on substrate in contact with a liquid mixture comprising mixture of solvent and non-solvent materials with respect to said polymeric film for a selected time period;

drying said polymeric film on substrate from said liquid mixture thereby providing a plurality of through pores in said polymeric film.

According to some embodiments, the polymeric film on substrate may be a roll of film, wherein regions of the roll being brought into contact with said liquid mixture in a in rolling fashion.

According to some embodiments, the formed pores may be through pores that penetrate both surfaces of the said film.

According to some embodiments, the method may be used in continuous, semi- continuous or batch line of production.

According to some embodiments, said polymeric film may be formed of hydrophobic polymer or copolymer.

According to some embodiments, said polymeric film may be formed out of at least one of: PET, PS, PMMA, PE, PP, Polyamide, Polyimide, PTFE, ETFE, PVC, PC, PES, ABS, PVA, PVAc, Cellulose acetate, cellulose nitrile, cellulose ether, PEEK, PVDF, Polyacrylonitrile, PDMS and all acrylic block co-polymer.

According to some embodiments, said polymeric film may be formed of PMMA-

PnBA.

According to some embodiments, said polymeric film has thickness between lOnm to 10mm.

According to some embodiments, said solvent material of the liquid mixture is selected as one or more liquid materials capable of dissolving said polymeric film. According to some embodiments, said solvent material is selected from: DCM, Chloroform, DMF, DMSO, Pentyl acetate, Ethyl acetate, Acetophenone, Cyclohexanone, l,4Dioxane, Xylene, Toluene, Benzene, and CS2. According to some embodiments, said non-solvent material is water or selected alcohol.

According to some embodiments, said liquid mixture has solvent material and non-solvent material at mixing ratio between 30:70 and 70:30.

According to some embodiments, said liquid mixture has solvent material and non-solvent material at mixing ratio between 45:55 and 55:45.

According to some embodiments, said non-stick coating on at least one surface of the substrate where said polymeric film is located provides for generation of pores penetrating through thickness of said polymeric film.

According to some embodiments, the technique may further comprise applying metallization on at least one face of said polymeric film after generating said plurality of through pores in said film. Said applying metallization on at least one face of said polymeric film may comprise utilizing vapor deposition metallization. The vapor deposition may be physical or chemical vapor deposition.

In some additional configurations, said applying metallization on at least one face of said polymeric film comprises utilizing at least one of electroless or electrodeposition method on at least one face of the film while retaining isolation from the other face of the film and inside walls of said plurality of pores in the film.

According to some embodiments, said bringing the polymeric film on substrate in contact with the liquid mixture comprising the mixture of solvent and non-solvent materials comprises immersing at least a portion of said polymeric film on substrate in said liquid mixture for period between 0.1 and 30 seconds.

According to some embodiments, said drying of said polymeric film on substrate from said liquid mixture comprises providing said polymeric film on substrate at drying conditions in temperature range between 0 and 250 degrees Celsius. The temperature range may be between 15 and 150 degrees Celsius.

According to some embodiments, said non-stick coating comprises at least one of Fluorinated polymer, ETFE, and silicone (polysiloxanes).

According to some embodiments, the technique may further comprise applying metallic layer on said film to provide template pattern to said metallic layer. According to some embodiments, the technique may further comprise selecting material composition of said polymeric film to provide adhesive properties, and applying metallic layer on the patterned film, thereby providing selected surface pattern to the metallic layer.

According to some embodiments, said patterned film may be metallized for use as electrical conducting network.

According to some embodiments, selection of production parameters to provide pore size and structure between adjacent pores, provides at least partially optically transparent conducting electrode. Such electrically conducting network may be used for at least one of: EMI shielding, antennas, transparent conductive films and defogging applications.

According to some embodiments, said electrically conducting network is configured to provide selected electrical or thermal conductivity and selected degree of transparency.

According to one another broad aspect, the present invention provides a patterned film produced by the method as described above.

According to some embodiments, the patterned film produced as described above may be configured for coating selected material to provide selected heat transfer properties, thereby enabling cooling of selected heat source.

According to some embodiments, the patterned film produced as described above may be configured for scattered visible light and to provide enhanced emissivity of IR radiation in the 3-5um and/or 8-12um wavelength atmospheric window

According to some embodiments, the patterned film produced as described above may be formed with pore size selected for filtering of selected wavelengths.

According to some embodiments, the patterned film produced as described above may be configured for filtering electrically charged specimens by determined by the pore size through the application of a suitable electrical field. BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

Fig. 1 schematically illustrates a technique for patterning of film according to some embodiments of the invention, utilizing liquid bath;

Fig. 2 schematically illustrates a technique for patterning of film according to some embodiments of the invention, utilizing spray or printing techniques;

Fig. 3 shows a flow chart exemplifying the method according to some embodiments of the present invention;

Fig. 4 shows an image of the formed patterned PMMA film prepared using DCM as solvent material according to some embodiments of the present invention;

Figs. 5A and 5B show microscopic images of PMMA film patterned using CHCb/MeOH 85/15 solution according to some embodiments of the present invention;

Figs. 6A and 6B show microscopic images of patterned PMMA block copolymer film patterned using 83% chloroform and 17% methanol for 7 seconds at temperature of 17.5 degrees Celsius according to some embodiments of the present invention;

Figs. 7A and 7B show microscopic images of patterned PMMA block copolymer film patterned using 83% chloroform and 17% methanol at 18.4 degrees Celsius for 8.5 seconds according to some embodiments of the present invention;

Figs. 8A and 8B show patterned PMMA block copolymer patterned using liquid mixture containing 82% chloroform and 18% methanol for 10 seconds at temperature of 20.5 degrees Celsius; and

Figs. 9A and 9B show metallized film based on patterned PMMA block copolymer film as shown in Figs. 8A and 8B. DETAILED DESCRIPTION OF EMBODIMENTS

As indicated above, the present invention provides a technique for use in production of patterned polymeric films. Reference is made to Fig. 1 exemplifying certain aspects of the present technique.

5 In the example of Fig. 1, a roll 110 carrying a polymeric film 100 (typically on a substrate) is used for large scale processing of the film 100 to apply / produce micro- and/or nano- structures (pores) in the film 100. Rollers Rl to R4 are used to pass the film 100 through a process stage including a liquid chamber 200 containing a selected liquid mixture and a drying chamber 300. As is also exemplified in Fig. 1, the polymeric film 10 100 may be applied on a substrate by physical or chemical deposition, e.g. by a deposition unit 150.

The liquid mixture placed in the liquid chamber 200 contains a mixture of at least two selected materials including at least one material that acts as a solvent with respect to the polymeric film material, and at least one material that is a non-solvent with respect 15 to the polymeric film material. The use of such mixture of solvent and non-solvent materials allows the liquid mixture to swell the material of the film at a limited rate and distribution. When the film 100 is transferred to the drying chamber 300, the liquid mixture evaporates leaving a plurality of pores in the film 100. At this stage the film 100 may be rolled onto a collection roll 120 or may pass forward for additional processes.

20 As exemplified in Fig. 1, the technique may provide roll to roll continuous production of film 110 having a pattern in form of plurality of pores. As indicated, the film is generally a flexible polymeric film and may have thickness between lOnm and lmm, and preferably between lOOnm and lOOum. The technique is not limited to any specific film width or length, and may be operated with the film width of more than 1cm,

25 and preferably between 30cm and 3m, and with the film length of above 30cm and preferably longer films (e.g. above 10m or above 100m). The continuous patterning technique forms microscopic 3D geometric features (pores) on at least one side of the film and preferably forms through pores extending through the thickness of the film. The pores are formed with size distribution having an average size in the range between lnm

30 and lmm and preferably between lOOnm and lOOum or between 5um and 20um In roll to roll continuous fabrication, the film may be pulled from an input roll 110, and each portion of the film passed through corresponding processing sections along the length of the film. The film may be passed on supporting/guiding rollers such as Rl to R4 as exemplified in Fig. 1, while portions thereof are passed through at least the liquid chamber 200 and the drying chamber 300. The rolls may be of web size of normally ~2m or a smaller ~30cm standard width.

The polymeric film 100 may be provided as a stand-alone film, or film applied or formed on a flexible, as well as rigid or semi-rigid, substrate. Generally, the inventors of the present invention have found that in order to produce pores passing through the thickness of the film, while being located on a substrate, a non-stick coating needs to be used coating at least one surface of the substrate film and located between the substrate and the polymeric film applied thereon.

Further, the film is exposed/immersed in the liquid mixture including at least one material that is solvent with respect to the polymeric material of the film 100 and at least one material that essentially does not dissolve the material of the polymeric film 100, thereby providing a solvent/non-solvent solution mixture. After exposing the film to the liquid mixture, the film is dried by evaporating the solvent material and subsequently the non-solvent material from the film. This evaporation causes formation of a microstructure where the non-solvent material acts as template for the structures/pores. In this connection it should be noted that the selection of the solvent and non-solvent materials is based on selection of the polymeric film 100 material, as well as the need to provide single phase liquid mixture. Thus, the solvent and non-solvent materials, and ratio between them, are selected to provide single phase liquid mixture.

The example of Fig. 1 illustrates the use of a bath of liquid mixture in the liquid chamber 200 where the film 100 is passed through the liquid bath. Reference is now made to Fig. 2 exemplifying additional technique where the liquid mixture is applied on the film 100 by brushing, printing or spraying of the liquid mixture of surface of the film 100. To this end, the technique may use one or more liquid ports 220 formed as brushes, injection heads, etc. The liquid mixture is preferably applied in uniform, or almost uniform manner on the surface of the polymeric film 100. Alternatively, the technique as exemplified in Fig. 2 may be used to provide non-uniform patterning by selectively applying the liquid mixture only to regions of the film 100 that are to be patterned. Generally, the formation of the micros tructures' pattern on the film is a result of self-arrangement of the non-solvent material upon evaporation of the liquid mixture. Typically, this may form relatively ordered structures, where a level of disorder may be determined by one or more of production parameters, such as solvent/non-solvent ratio, ambient moisture drying temperature, and amount of liquid mixture to which the film is exposed. Selection of these manufacturing parameters provides structures' pattern taking form of ordered or disordered pore structure. Generally, the shapes and arrangement of the structures depend on the shape and arrangement of drops of the non-solvent liquid material and/or adhered moisture when evaporating. More specifically, the solvent material of the liquid mixture acts on the film 100 material. While drying, the solvent material evaporates leaving skeleton of the film material, which re-solidifies in accordance with the pattern formed by drops of the non-solvent material. The shape of the structure (defined by the shape and arrangement of the non- solvent drops) can be manipulated also by application of external forces, such as electric and/or magnetic field, air flow or other external shaping forces.

Various additional controlling techniques enable to affect and determine size, shape and arrangement of the pores and structures formed on the polymeric film according to the present technique. For example, the use of stand-alone polymeric film, or polymeric film applied on a substrate using non-stick coating, enables formation of through pores penetrating through the thickness of the film (given sufficient exposure to the liquid mixture). Using proper mixture ratio and time of exposure of the film to the liquid mixture the pores may be formed while varying in shape through thickness of the film, forming two or more interconnected layers in which the lateral dimension (diameter) of the pores changes gradually. In another configurations, the pores are not penetrating to the other side (i.e. are in the form of surface grooves) leaving a thin layer on the bottom of the film. In some other configurations, the film may be patterned by pores that do not penetrate through the film but form structures on one or both surfaces of the film.

For example, in some configurations, a top layer of the film may be subsequently peeled off, creating pyramids (pyramid-like structures) allowing increased contact angle of the patterned film with fluids. This enables formation of hydrophobic or oleophobic surfaces that do not wet by selected fluids. In some embodiments, the geometry allows permeation of low surface tension liquids and prohibits high surface tension liquids from permeation.

Additionally, as indicated above, the patterning may be performed only on selected sections/regions of the film. This may be done using a mask, or by selective printing of the liquid mixture on the selected regions of the film. Thus, the liquid mixture can be deposited in the desired geometry/pattern on the film and induce the formation of structures in selected regions or variation in structures' properties between the regions.

Additional pattern variations may be provided by mechanic stretching of the film or application of external field(s) on the film. This may be while drying, after the film formation, or during both of these processes. Generally, stretching may provide preferential orientation for the pores, being oval or elongated pores, having one longer dimension as compared to the other. An external electric field may be applied on the film to induce a-symmetry in the pores creation.

In some embodiments, the liquid mixture may also include selected nanoparticles (e.g. metallic, metal oxides, organic). These nanoparticles may become embedded into the pores in the film providing various selected properties to the patterned film. For example, platinum coated nickel particles may be used in the liquid mixture so that the particles are incorporated/embedded in the final patterned film/structure. Such particles may act as catalyst for charge selective film/electrode, e.g. Proton Exchange Membrane (PEM) suitable for use in fuel cells, where a properly patterned film may be used as a membrane acting as a template for the charge selective (e.g. proton exchange) material. Additional nanoparticles may be used to provide anti-bacterial properties. For example, silver nanoparticles may be used in forming a patterned film having selected structure properties suitable for selected medical, wellness or other health related applications. In some specific examples, the patterned film may be configured with a selected surface structure and interaction properties to provide efficient transmission, e.g. 'breathing' properties. This, for example, may be suitable for use as a medical bandage fabric, e.g. plasterband-aids, etc. Alternatively, selected nanoparticles and pattern formation of the film may provide antibacterial functionalization, e.g. by metallization of a metallic layer of silver or copper on the film patterned surface. In yet another example ceramic or other nanoparticles may be used to provide the patterned film having improved abrasion, heat and/or chemical resistance and durability. In addition, increased thermal, chemical and mechanical durability and resistance may be obtained by the crosslinking of the polymeric membrane or by the addition of a second polymeric system which creates a reinforcing network throughout the so formed patterned film.

After forming the desired structure pattern of the film, the present technique may be utilized to provide additional selected properties to the resulting patterned film for various applications. For example, the patterned film may be coated by one or more metallic layers on a selected surface thereof, to provide a metalized membrane. For example, the technique may include depositing one or more metallic layers on one surface of the patterned film. For example, the film may be coated by vapor deposition techniques with metallic layers of selected thickness. Generally, pores formed in the film as described above, may have negative slope with respect to at least one surface of the film. This may be used to prevent coating of the pores and/or of the other surface of the film, ensuring separation between coating of top and bottom faces of the film thus allowing to provide electrically insulated contacts of the faces of the film. The patterned film may also be coated by electroless or electrodeposition from solution or printed with a conductive ink. In these techniques, the pores geometry may be used to exclude the liquid due to surface tension and thus does not coat the inside of the pores. These coated patterned films may be used for various applications including, but not limited to, batteries, fuel cells, supercapacitors and generally in electric applications where matter should be allowed to pass between electrodes (e.g. ions).

In some examples, the patterned film may be formed with pores' density and dimension (diameter) properties to provide, with material of the film, selected transparency. Such transparent or partially transparent film may be metalized for use as Transparent Conducting Films for various applications. Such transparent conducting film may be configured with selected conductivity that may be superior to ITO transparent electrodes.

Another exemplary application, where films patterned according to the present technique may be advantageously used includes passive cooling applications. In such applications, pore sizes may be selected by patterning technique parameters to enhance reflectivity in visual and near IR, while allowing high emissivity in selected IR windows (e.g. at 3-5 μηι or 8-12 μηι). Selected pattern properties of the film may provide geometrically enhanced scattering for selected wavelength ranges (e.g. shorter wavelengths) and amplify transmission of other wavelength ranges (e.g. long IR wavelengths). Such pattern properties may be determined by matching certain pore properties (e.g. pore diameters) to the desired wavelength ranges.

Additional applications may include cell culture film, speakers sound damping, optical phase change films e.g. quarter wave, polarizers, filters, displays, medical plasters, etc.

Further, films patterned according to the present technique may be used in combined structures. For example, two or more films having selected (different or similar) patterns may be used in succession for forming three-dimensional film structures. Such structures may be used for trapping of particles of selected size properties.

Another exemplary application includes bottom electrode in solar panels (solar cells) configurations, where the patterned film including through pores allows contact between optically active layer, and top and bottom electrodes within selected maximal radius.

In this connection, the resulting film may be patterned with micrometric pores passing through the thickness of the film. This enables the film to be used as basis for electrode arrangement allowing top and bottom electrically separated electrodes having micrometric distance between them at each point along the surface of the electrode arrangement. More specifically, in this configuration, one electrode is the conductive coating on one side of the film and the other electrode is a conductive coating on the other side of the film or a substrate on top of which the film is laminated. This approach provides creation of two electrodes with micrometric proximity and without shorts. One or both conducting electrodes may be charge selective (selected metals) or coated with charge selective material(s) to provide effective charge collection in e.g. photovoltaic cells.

The production of films with blind holes creates 'micro-cups' of controlled volume which may be used in medical or biological applications, allowing production and/or capture of a multitude of microscopic biological samples with the same 'history' which may be further manipulated and/or studied thus creating a large statistical basis for increased validity of results and conclusions.

In this connection, reference is made to Fig. 3 exemplifying a flow diagram illustrating the method of present technique for creation / formation of a patterned film 1080. In this example, the present technique utilizes patterning of a film 1040 using selected liquid mixture 1050, by bringing the liquid mixture in contact with the film 1060 and drying of the film 1070. In some configuration, the technique may include providing a substrate carrier 1010, where the substrate carrier may have, or be applied with a coating thereon 1020, having selected surface properties (e.g. non-stick coating). The film may be placed or applied on the substrate 1030 for easy use. Further, the resulting patterned film may undergo stretching by external field 1075 when in contact with the mixture, while drying or after. Thus, the present technique provides the patterned film having selected pattern properties based on / defined by preparation parameters. Such parameters include film thickness, composition and relative ratios of the solvent and non-solvent materials in the mixture, interaction time and drying. Additional parameters include temperature and humidity levels in the mixture and while drying.

The inventors have tested the above described technique in several embodiments/variations as brought herein in examples using specific combinations of solvent and non-solvent material selections and films selection.

Example 1

A 100 μπι thick PET carrier substrate film is coated by 30 μπι thick (wet thickness) from a solution of 1 :10 mass ratio of PMMA 350,000 Mw in Ethyl acetate by gravure coater inline. Next, the casted on the carrier film passes through a drying chamber for 10s at 25 degrees Celsius and RH of 50% to evaporate the Ethyl acetate and form PMMA film in thickness of about 3um. After drying, the film passes through a bath containing a solvent/non-solvent mixture solution containing 83% Chloroform as solvent material and 17% Methanol (MeOH) as the non-solvent material. The liquid mixture was also tested with addition of 9% water or 0.5% toluene. The film is partly solvated and exits at 5 degrees above horizontal to a drying chamber at temperature of 25 degrees Celsius and relative humidity (RH) of 50% for 10s. During this stage the chloroform evaporates first and the MeOH (wet) forms droplets that self-assemble to create uniform droplets with diameter of lOum on the film, diameter before evaporating themselves and leaving pores of diameter of 10 um. The film is subsequently cured at 90 degrees Celsius for 1 min to strengthen its physical properties. In another test, the PMMA Chloroform solution also includes 1 % w/w HD A (hexadecylamine) mixed therein to yield larger pores in the patterned film. Alternatively, a PSS water soluble release layer was applied on the thick PET carrier substrate before the PMMA film to provide non-stick coating. Fig. 4 shows an image of the formed patterned film prepared as described above, using DCM instead of chloroform as solvent material. In another test, the liquid mixture includes 10% Methanol.

Example 2

A PMMA film was prepared by blade coating from 5% to 15% w/w 350kD PMMA solution in CHCb coated onto an aluminum foil and letting it air dry. A CHCb/MeOH 85/15 solution was prepared providing solvent/non-solvent material mixture. The supported film was dipped in the solvent/non-solvent mixture for 1 to 60 seconds and pulled out of the solution to allow the pattern formation.

Reference is made to Figs. 5A and 5B showing microscopic images of the resulting patterned films. Similar testing was conducted using PS -10% as polymeric film over PMMA.

Example 3

A PET sheet coated by an ALD Ti02 thin layer is cleaned with acetone and EtOH. then placed on a glass plate and wiped with a chem-wipe.

5% w/w PMMA-PnBA co-polymer is dissolved in chloroform. The PMMA- PnBA solution is applied by bar (meyer-rod) coat to the PET, with the bar set to 200um, and dried. The resulting 20um dry film is dipped in a 10% v/v MeOH in chloroform for 40s and moderately pulled out at a steady pace. The sample is dried while hanging with humidity is in the range of 55%-70% in the hood and lab and the temp is 25C-28C providing patterned PMMA-PnBA co-polymer film.

Similar configurations were tested with ETFE, PTFE, CPP substrates and other substrates composed of or coated with 'non-stick' substances with a high contact angle. Additional coating methods providing film of the substrate were tested including gravure method and spray method. The film was dipped into the liquid mixture as well as interacted with the mixture by spraying the mixture on the film.

Example 4

PMMA block copolymer (using LB-550 commercially available material) was dissolved at 20% w/w in Ethyl-Acetate at 80 degrees Celsius. The solution was applied on Silicone on plastic substrate that was previous cleaned by acetone and ethanol and dried at 80 degrees to provide a film of 3-4 um. The film was dipped into liquid mixture containing 86% chloroform and 14% methanol for 15 seconds at temperature of 20.2 degrees Celsius, with 83% relative humidity. The wet film was left for about 3 seconds and dried with nitrogen flow of 15ml/minute.

Similar testing was done with liquid mixture containing 83% chloroform and 17% methanol for 7 seconds at temperature of 17.5 degrees Celsius, with 80% relative humidity, and where the film was dried immediately after leaving the liquid mixture. Figs. 6A and 6B show microscopic images of the resulting patterned film with marked scale for size comparison.

Additional testing was conducted with the film dipped into liquid mixture at temperature of 18.4 degrees Celsius for 8.5 seconds, with 85% relative humidity. The resulting film is exemplified in Figs. 7A and 7B.

Example 5

PMMA block copolymer (using LB-550 commercially available material) was dissolved at 20% w/w in Ethyl-Acetate at 80 degrees Celsius. Additional solution used 1.5% Ti02, 5% EtCe, 0.5% Terpineol. Additional 1.5% Ti02 nanoparticles were added to the solution. The solution was sonicated at 40% power for 10 seconds and allowed to rest for 20 seconds, this sonication was repeated for 20 minutes to fully dissolve the PMMA. The solution was applied on siliconized (sticker) paper substrate that to provide a film of 4-5 um. Additional PMMA layer was applied on the substrate on its bottom side. The film was dipped into liquid mixture containing 82% chloroform and 18% methanol for 10 seconds at temperature of 20.5 degrees Celsius, with 85% relative humidity. The wet film was dried with nitrogen flow of 15ml/minute. The resulting patterned film is exemplified in Figs. 8A and 8B. Example 6: metallized membrane

The patterned film formed in example 5 and shown in Figs. 8A and 8B was transferred from the siliconized paper to a PVA coated PET film (deposited by meyer rod from a 10% solution of PVA 40Kd in EtAc followed by drying at 60C for 5 min) by means of passing the two substrates face-to-face through a heated rolling press. The transferred membrane is then introduced to the vacuum chamber of a thermal evaporator and pumped down to lxlO ^"6 torr. The membrane is then coated by a lOnm Cr adhesion layer followed by a 150 nm aluminum layer. After evaporation the coated membrane can be transferred to any substrate by dissolving of the PVA sacrificial layer in water. Reference is made to Figs. 9A and 9B showing exemplary metallized films.

As indicated from the above examples and the figures, various parameters affect formation (size, shape and depth) of the pores formed in the film. The higher the relative humidity, the smaller the average pore size. This may be associated with coagulation of the non-solvent material and absorption of water into the non-solvent material while drying. Selection of temperature of the liquid mixture also affects size and density of the pores. Lower temperature provides smaller and more dense pores, while limiting depth of the pores, providing pores of 1-2μπι average diameter. The inventors have identified that, in some configuration, optimal through pores may be formed at temperature of 17 degrees for thin film on ETFE, and at temperature of 20-23 degrees for film on sticker paper. Thicker films may be patterned at temperature above 20 degrees. Exposure time to the liquid mixture also affects the pores size, however increase period of exposure may reduce thickness of the film. Exposure period of about 10 seconds was found suitable for Film on sticker paper to provide through pores in the film. Generally, the use of Nitrogen flow for drying may increase uniformity of the pattern. High flow rates may limit creation of through pores, while lower flow rate may form larger pores with limited uniformity. Mixing ratio of the liquid mixture determine dissolving rate of the film and thus generation and size of the pores therein. Increased amounts of the non-solvent material (e.g. Methanol) requires longer time for the film to dissolve and thus forms increase pores amount and smaller pore size, reduced amount of the non-solvent material results in fewer but larger pores. To provide uniform through-pores that transcend the full thickness of the film, the film is preferably uniform in thickness and applied on low surface energy layer (non-stick, hydrophobic) on the substrate (e.g. using ETFE, sticker paper or wax covered substrate (e.g. backing paper).

Thus, the present technique provides a robust and efficient method for patterning polymeric films with micro- and/or nano-structures (e.g. pores), including generating through pores (holes) in the film.