Patterned porous material surfaces

Abstract

The filtration media includes a layer of porous material having a patterned outer surface with a plurality of structures, each structure in the plurality of configurations having at least a predetermined height based on an anticipated contaminant, and a spacing between each structure in a pair of the plurality of configurations is at most a predetermined spacing based on an anticipated contaminant.

Description

[Technical field]

[0001] Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 170,104 (filed April 2, 2021), the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE This disclosure relates generally to patterned surfaces of porous materials to increase their hydrophobicity and / or oleophobicity, and methods for forming them. [Background technology]

[0003] Many enclosures need to be vented to the outside atmosphere to release waste gases or resolve pressure differentials. Venting may be necessary as a result of temperature fluctuations, altitude changes, and vapor pressure of contained liquids. Vents, or venting media, allow gases to pass therethrough to equalize pressure, while excluding liquids and solids to protect the internal components. However, in some applications (e.g., automotive, medical, construction), the venting or filter media is exposed to liquid contaminants with low surface tension and / or high viscosity that are not easily dislodged from the porous venting media. Summary of the Invention [Problem to be solved by the invention]

[0004] These contaminants then block the pores of the media, reducing or redirecting the flow of the air being extracted. Certain coatings have been used to improve the hydrophobic and / or oleophobic properties of the venting media, but physical modifications to the surface of the venting material may provide improved exclusion of low surface tension and / or high viscosity contaminants alone, or in combination with a coating. [Means for solving the problem]

[0005] Embodiments described herein are directed to a filtration medium that includes a layer of porous material having a patterned outer surface including a plurality of pillars, where each pillar in the plurality has a predetermined height based at least on an expected contaminant, and where the spacing between each pillar in a pair of the plurality is at most the predetermined spacing based on the expected contaminant.

[0006] Another embodiment is directed to a filtration medium that includes a layer of porous material having an outer surface that includes a patterned plurality of raised structures, each of the plurality of configurations having a predetermined height based on anticipated contaminants, and a spacing between each of the plurality of configurations of raised structures that is at most the predetermined spacing based on anticipated contaminants.

[0007] Another embodiment is directed to a filtration media including a first layer of porous material and a second layer of material disposed on the first layer, the second layer having a patterned outer surface including a plurality of raised structures, each raised structure in the plurality of configurations having at least a predetermined height based on an anticipated contaminant, and a spacing between each raised structure in a pair of the plurality of configurations is at most the predetermined spacing based on an anticipated contaminant.

[0008] Another embodiment is directed to a filtration medium including a layer of porous material having an outer surface including a hierarchical structure and a patterned plurality of raised structures, each of the plurality of configurations having a predetermined height based on anticipated contaminants, and a spacing between each of the plurality of configurations of raised structures is at most the predetermined spacing based on anticipated contaminants.

[0009] Another embodiment is directed to a venting apparatus including an opening configured to vent an enclosure, and a venting element secured within the venting apparatus to form a liquid-tight, gas-permeable seal at the opening, the venting element including a porous material having a surface including a patterned plurality of raised structures, where each raised structure in the plurality of configurations has a height that is at least predetermined based on anticipated contaminants, and where a spacing between each raised structure in a pair of the plurality of configurations is at most predetermined based on anticipated contaminants.

[0010] A further embodiment is directed to a method including providing a layer of porous material and a stamp having a patterned outer surface corresponding to a negative of a pattern including a plurality of raised structures, each of the plurality of raised structures having at least a predetermined height based on anticipated contaminants, and a spacing between each of the raised structures in a pair of the plurality of raised structures being at most a predetermined spacing based on anticipated contaminants, the method further including applying the stamp to a first surface of the layer of porous material at a predetermined temperature and pressure to form a plurality of patterns of raised structures having predetermined heights and spacings on the first surface of the layer of porous material.

[0011] The foregoing summary is not intended to describe each disclosed embodiment or to represent every example disclosed herein. The figures and detailed description that follow more particularly exemplify illustrative embodiments.

[0012] In the following description, reference is made to the following drawings, where the same reference numerals are used in the various drawings to identify similar or identical components. However, the use of a numeral designation for a component in one drawing does not limit the component labeled with the same numeral in another drawing. The drawings are not necessarily drawn to scale. [Brief description of the drawings]

[0013] [Figure 1A] A diagram of a droplet on a patterned surface in the Wenzel state; [Figure 1B] A diagram of a droplet on a patterned surface in the Cassie-Baxter state; [Diagram 2] A plot of the roll-off angle for a droplet on a patterned surface; [Figure 3A] 1 is a cross-sectional view of a patterned surface in accordance with certain embodiments; [Figure 3B] FIG. 2 is a top-down view of a patterned surface in accordance with certain embodiments; [Figure 3C] FIG. 2 is a top view of a patterned surface having square shaped structures according to certain embodiments; [Figure 3D] FIG. 2 is a top view of a patterned surface having hexagonal shaped structures according to certain embodiments; [Figure 3E] FIG. 2 is a top view of a patterned surface in accordance with certain embodiments; [Figure 3F] 1 is a diagram illustrating the contact line force in certain embodiments; [Figure 4A] FIG. 2 is a diagram of a patterned surface having a pattern solid fraction of about 0.25 in certain embodiments; [Figure 4B] FIG. 2 is a diagram of a patterned surface having a pattern entity fraction of about 0.5 in certain embodiments; [Figure 5A] 1 is a graph of contact angle as a function of surface pattern entity fraction in certain embodiments; [Figure 5B] 1 is an image of a droplet on an unpatterned surface of a porous material; [Figure 5C] 1 is an image of a droplet on a patterned surface of a porous material in certain embodiments; [Figure 6] 1 is an image of a hierarchically structured material according to certain embodiments; [Figure 7] 1 is a graph of contact angle as a function of surface tension for unpatterned and patterned materials according to certain embodiments; [Figure 8A] 1 is a graph of transmittance as a function of contamination on unpatterned and patterned materials in certain embodiments; [Figure 8B] This is an image of contamination on non-patterned material; [Figure 8C] 8B is an image of the contaminant of FIG. 8B on the patterned material of FIG. 8B; [Figure 9A] 1 is an image of a patterned surface of rib-shaped structures in certain embodiments; [Figure 9B] The profile measured on the patterned surface in Figure 9A; [Figure 10] 1 is a graph of slide angle as a function of pattern height in certain embodiments; [Figure 11] 1 is a graph of slide angle as a function of surface tension for different spacing patterns according to certain embodiments; [Figure 12] 1 is a graph of sliding angle as a function of surface tension for a first porous material according to certain embodiments; [Figure 13A] 1 is a graph of permeability reduction as a function of pressure for low porosity materials in certain embodiments; [Figure 13B] 1 is a graph of permeability reduction as a function of pressure for highly porous materials in certain embodiments; [Figure 14A] FIG. 2 is a cross-sectional view of a patterned composite material according to certain embodiments; [Figure 14B] FIG. 2 is a cross-sectional view of a patterned composite material according to certain embodiments; [Figure 15] 1 is a flow diagram of a method for forming a patterned porous material surface according to certain embodiments; [Figure 16A] FIG. 1 illustrates a method for forming a patterned porous material surface according to certain embodiments; [Figure 16B] FIG. 1 illustrates a method for forming a patterned porous material surface in certain embodiments; and [Figure 17] FIG. 2 illustrates a cross-sectional view of a porous material having a coating on a patterned surface according to certain embodiments. [Figure 18] FIG. 2 is a schematic cross-sectional side view of an article to be degassed according to an embodiment. [Figure 19] FIG. 2 is a schematic cross-sectional side view of an embodiment of a vented battery pack. [Figure 20A] FIG. 2 is a schematic cross-sectional side view of a component of a package that is vented according to an embodiment. [Figure 20B] FIG. 2 is a schematic cross-sectional side view of a component of a package that is vented according to an embodiment. [Figure 20C] FIG. 2 is a schematic cross-sectional side view of a component of a package that is vented according to an embodiment. [Figure 21A] FIG. 2 is a schematic cross-sectional detail of a component of a package that is vented according to an embodiment. [Figure 21B] FIG. 2 is a schematic cross-sectional detail of a component of a package that is vented according to an embodiment. [Figure 21C] FIG. 2 is a schematic cross-sectional detail of a component of a package that is vented according to an embodiment. [Figure 22A] 1 is a microscope image of the material produced in Example 5. [Figure 22B] 1 is a microscope image of the material produced in Example 5. [Figure 23A] 1 is a microscope image of the material produced in Example 6. [Figure 23B] 23B is a schematic depiction of the material of FIG. 23A. [Figure 23C] FIG. 23C is a cross-sectional view of the material of FIG. 23B. [Figure 24] 1 is a microscope image of the material produced in Example 7. [Diagram 25] 1 is a microscope image of a comparative material in Example 7. [Figure 26] 1 is a microscope image of the material produced in Example 8. [Figure 27] 1 is a graph of the transmittance obtained in Example 9.

[0014] definition All headings provided herein are for the convenience of the reader and should not be construed as limiting the meaning of the text that follows the heading, unless specifically stated otherwise.

[0015] The indefinite articles "a" and "an" and the definite article "the" are not intended to refer to a singular entity only, but are inclusive of the entire type of which one specific example is given for illustrative purposes. The terms "a," "an," and "the" are used interchangeably with the term "at least one." The phrases "at least one of" and "comprises at least one of" preceding listed items refer to any one of the listed items and to any combination of two or more of the various listed items.

[0016] As used herein, the term "or" is generally used in its usual sense and includes "and / or" unless expressly stated otherwise. The term "and / or" (when used) refers to one or all of the listed elements or any combination of two or more of the listed elements. Furthermore, "eg" is used as an abbreviation of the Latin "exempli gratia," meaning "for example."

[0017] When a numerical range is used by indicating the endpoints, all numerical values ​​within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and all ranges within that range are included. Furthermore, unless otherwise indicated, all numerical values ​​expressing quantities and all terms expressing direction / orientation (e.g., vertical, horizontal, parallel, orthogonal, etc.) in this specification and claims are to be understood as being modified in all instances by the term "about." Thus, unless otherwise indicated, the parameters referred to in the foregoing specification and the appended claims are approximations and may be varied depending on the desired properties desired to be obtained by those of skill in the art using the teachings disclosed herein. As used herein, the term "about" in combination with numerical values ​​is to be understood to have the same meaning as "approximately" and to include typical error ranges, e.g., ±5% of the stated value.

[0018] Relative terms, such as proximal, distal, left, right, forward, rearward, top, bottom, side, upper, lower, horizontal, vertical, etc., may be used in this disclosure to simplify the description. However, such relative terms are not intended to limit the scope of the invention in any way. For example, terms such as left, right, forward, rear, top, bottom, lateral, upper, lower, horizontal, vertical, etc., are from the perspective as viewed on that particular feature.

[0019] The various directions referenced herein, such as "top," "bottom," "left," "right," "upper," "lower," and other directions or orientations, are described herein for purposes of clarity and brevity, and are not intended to limit the actual device or system. The devices and systems described herein can be used in many directions and orientations.

[0020] As used herein, terms such as "have," "having," "include," "including," "comprise," "comprising," and the like are used in an open-ended manner and generally mean "including, but not limited to." Terms such as "consisting essentially of," "consisting of," and the like will be understood to be subsumed within "comprising," and the like. As used herein, the term "consisting essentially of," when it relates to a composition, product, method, and the like, means that the components of the composition, product, method, and the like are limited to the recited components, as well as various other components that do not materially affect the basic and novel characteristics of the composition, product, method, and the like.

[0021] The terms "preferred" or "preferably" refer to an embodiment that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred, in the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of this disclosure (including the claims).

[0022] As used herein, the term "substantially" should be understood to have the same meaning as "significantly" and to modify the term that follows by at least about 90%, at least about 95%, or at least about 98%. As used herein, the term "not substantially" should be understood to have the same meaning as "not significantly" and to have the opposite meaning of "substantially", i.e., to modify the term that follows by no more than 10%, no more than 5%, or no more than 2%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present disclosure relates to a filtration and degassing media capable of resisting fouling by repelling and releasing liquid contaminants that come into contact with the media, the media including a porous material having a patterned surface having a plurality of raised structures disposed thereon.

[0024] The terms "filter media" and "venting media" are used interchangeably herein, and the term "venting media" simply refers to the filter media used to provide venting.

[0025] The raised pattern features or structures on a surface change the properties of the surface in various ways. For example, the raised surface pattern can change various omniphobic surface properties of liquid droplets (e.g., hydrophobicity, oleophobicity, etc.), adhesion (improvement or decrease), anti-fouling behavior, and designed roll-off behavior. The formation of a raised surface pattern in a degassing or filtration medium can improve the hydrophobicity and / or oleophobicity to improve the rejection of liquid contaminants, including those with a surface tension of 72 mN / m or less. The patterning can also be combined with a coating (e.g., a short-chain fluoropolymer coating) to achieve high oleophobicity without the use of bio-persistent chemicals, e.g., long-chain perfluoroalkyl substances (PFAS).

[0026] With or without coating, patterned filtration media can improve performance and life in various degassing applications, such as integrated degassing modules for gas turbine systems, medical devices, packaging, batteries, and powertrain systems. These environments and others expose the filtration media to potential liquid contaminants that are difficult to remove from the surface of the filtration media. If the contaminant droplets are not removed or cleanly removed (e.g., leaving residual traces), the contaminants can block pores in the filtration media, blocking or redirecting gas flow and reducing the performance and life of the degassing or filtration media. By controlling the height and spacing of the structures, it is possible to design structured patterns to improve the hydrophobicity and / or oleophobicity of the degassing or filtration media for anticipated contaminants.

[0027] 1A and 1B show different states of a droplet on a hydrophobic and / or oleophobic material with a patterned surface. In FIG. 1A, a droplet 106 penetrates a microstructure 104 such that the droplet 106 reaches the surface of the material 102. This state is known as the Wenzel state and is expressed by the cosθ * =r cosθ, where θ * represents the apparent contact angle between the droplet 106 and the surface of the raised structures 104, θ is the equilibrium contact angle on a smooth surface, and r represents the roughness of the surface. The contact angle is the angle measured through the droplet when the liquid-gas interface is in contact with the solid surface. Hydrophobic and oleophobic materials are defined as materials with a contact angle greater than 90°, and superhydrophobic materials have a contact angle greater than 150°. The equilibrium contact angle can be estimated from Young's equation. In the Wenzel state, the increase in the contact angle is attributed to the increased surface area of ​​the textured / structured surface.

[0028] 1B, the droplet 106 rests on the surface of the raised structures 104 and does not penetrate to the surface of the material 102. Rather, the droplet 106 forms a meniscus or menisci between two or more raised structures 104, leaving a pocket of air between the droplet 106 and the surface of the raised structures. This condition is known as the Cassie-Baxter condition, and is expressed as a function of cosθ * =φ s It can be written as (1+cosθ)-1, where θ * represents the apparent contact angle between the droplet 106 and the surface of the raised structures 104, θ is the equilibrium contact angle on a smooth surface, and φ s is the solid fraction of the surface. For materials that are permeable to gases but impermeable to liquids, the material can be designed with a patterned surface to obtain Cassie-Baxter conditions for liquids (e.g., contaminants) that are expected to come into contact with the material.

[0029] In addition to the Cassie-Baxter condition, the patterned surface of the porous material may be designed to provide a roll-off angle such that liquid on the surface is easily removed. The concept of roll-off angle is illustrated in FIG. 2. The roll-off angle is the tilt angle at which a substrate, e.g., a patterned porous material, is positioned such that a droplet (e.g., a droplet of contaminant) is removed and rolls off the substrate. As seen in the figure, this can be understood as the angle 208 at which a substrate 202 having a patterned surface 204 is tilted such that the adhesive force acting on the droplet material 206 is less than the force of gravity. Thus, the roll-off angle can be considered as a measure of the adhesive force of the liquid contaminant to the substrate and is related to the ability of the substrate to avoid clogging by repelling liquid contaminants such as oil. The roll-off angle is measured using a drop size of at least 5 μL and a tilt speed of 2° / sec. In this specification, the roll-off angle is determined for a drop size of 20 μL unless otherwise stated. A lower sliding angle indicates improved repellency. If the droplets do not slide off, the porous material may become clogged or plugged, reducing the breathability of the material. In some instances, the droplets may slide off but leave behind material that reduces the breathability of the material. On the other hand, a lower angle of clearing the droplets increases the functionality and lifespan of the porous material when used as a venting material. As described in more detail below, the sliding angle on a porous material can be reduced using patterned surfaces designed with predefined parameters.

[0030] The dimensions of the patterned surface are described in relation to Figures 3A-3F. Figure 3A illustrates the dimensions of the patterned surface, e.g., the dimensions of the porous material. Exemplary porous materials that can be patterned as described herein can include woven materials, nonwoven materials (e.g., wet-laid), electrospun fiber mats, membranes, including polypropylene, polyethylene, polyester, polysulfone, polyethersulfone, expanded polytetrafluoroethylene, polyvinylidene fluoride, polyamide (nylon), polyacrylonitrile, polycarbonate, or cellulose acetate. The dimensions of the structures can range from greater than 300 nm, although the structures discussed herein can generally have dimensions (e.g., widths) in the range of 0.5 μm to 500 μm. Material 302 includes a plurality of structures 304 formed on at least one surface. Structures 304 have a height H304 and can have a variety of shapes. For example, the structures may take the form of pillars having a square, circular, or polygonal cross-sectional shape, ribs having a rectangular or square cross-sectional shape, or splines of a defined width, and combinations thereof. The structures further have a pitch p304, which is the center-to-center spacing between two adjacent structures. The height and / or pitch may be substantially uniform among the multiple raised structures, or one or both may vary.

[0031] The plurality of raised structures may form a pattern on the surface of the material. An example of a pattern is shown in FIG. 3B, which includes a first structure 304A and an adjacent structure 304B. The illustrated pattern is a 4×4 array of square shaped structures with a uniform pitch, but the pattern may include different shapes, multiple shapes, different pitches, and / or different numbers of structures in the rows and / or columns. In alternative embodiments, the patterns may have composite shapes, including composite combinations of the above structures. The patterns may be regular or irregular in shape. The illustrated pattern includes square shaped structures with a uniform pitch, so the disposition factor A (number of raised structures per unit surface area) is 1, and the unit surface area is p 2 The raised structures 304 have a width s 304. The height h 304 and pitch p 304 (in some cases commonly referred to as spacing) of the pattern structures have been found to affect the sliding angle and can be tailored to the contaminant being considered.

[0032] For a given contaminant, the minimum height that achieves the desired sliding angle can be calculated using Equation 1:

number

number

[0033] In embodiments where the structure is linear, as shown in FIG. 3E, L is p 2 is the perimeter of the inner rectangle (2s+2p, as seen in FIG. 3E), and the pattern entity fraction is

number

[0034] The height shown in Equation 1 is the minimum height to achieve the desired slide angle. However, one or more structures in the pattern may have a height that exceeds the calculated value. In one embodiment, all or substantially all of the structures in the pattern have a height that meets or exceeds the calculated value. In some embodiments, the pattern includes raised structures of a plurality of predetermined heights. For example, a first portion of the plurality of raised structures may have a first height and a second portion of the plurality of raised structures may have a second height. However, in a preferred embodiment, each of the predetermined heights will meet or exceed the predetermined height calculated using Equation 1.

[0035] In one embodiment, the porous material has a patterned surface with a plurality of raised structures. The raised structures have a height of 1 μm or more, 3 μm or more, 5 μm or more, 8 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more. The raised structures have a height of 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, 12 μm or less, or 10 μm or less. A suitable height range for the raised structures may be selected based on one or more contaminants to which the material will be exposed during its intended use. For example, if the material will be exposed to contaminants having a surface tension in the range of 25 mN / m to 80 mN / m (or, for example, in the range of 25 mN / m to 30 mN / m), the raised structures may have a height of 2 μm to 40 μm, 4 μm to 30 μm, 5 μm to 20 μm, or 6 μm to 15 μm. In some such cases, the raised structures may have a height of less than 12 μm.

[0036] When the raised structures are formed by imprinting, the raised structures are formed by compressing the material around the raised structures. Thus, when the raised structures are formed on a porous medium by imprinting, a raised structure having a lower height corresponds to a lower compression of the medium. In such a case, a lower height is preferred to maintain the permeability of the porous material. Examples of heights of such structures include about 1 μm to 30 μm, 1 μm to 15 μm, and 1 μm to 10 μm.

[0037] The maximum pitch to achieve the desired repellency and slide angle in a structure can be calculated using Equation 3:

number

[0038] Tangential force F CL is defined as the normal component of the tangential force and is expressed in Equation 4:

number

[0039] In addition, when designing a pattern to achieve a desired repellency and slide angle, the width of the raised structures in the pattern can be determined by the Cassie-Baxter equation, shown in Equation 5 below: cosθ * =φ s (1+cosθ)-1 Equation 5 Here, θ * represents the apparent contact angle between the droplet and the surface of the structure, and φ s is the pattern substance fraction of the patterned surface. Using these equations, the height and spacing of the features of the pattern can be predicted and designed, allowing control over the sliding angle of the material in relation to anticipated contaminants.

[0040] In one embodiment, the porous material having a patterned surface with the plurality of raised structures exhibits a desired contact angle when contacted with a liquid contaminant. The contact angle of the patterned surface can be higher than the contact angle of the same material without the pattern. The contact angle of the patterned surface can be at least 5°, at least 15°, at least 20°, or at least 25° higher than the same material without the pattern. There is no desired upper limit to the improvement in contact angle, and the contact angle can be up to 180°. In some embodiments, the porous material having a patterned surface with the plurality of raised structures exhibits superhydrophobicity to contaminants, exhibiting a contact angle of 150° or more. Such materials can be superhydrophobic or superoleophobic. The contact angle can be measured by various known methods. For example, the contact angle can be measured using a contact angle meter, for example, as described in Example 1.

[0041] In one embodiment, the porous material having a patterned surface with a plurality of raised structures exhibits a desired receding contact angle when contacted with a liquid contaminant. The receding contact angle of the patterned surface can be higher than the receding contact angle of the same material without the pattern. The receding contact angle of the patterned surface can be 50° or more, 60° or more, 70° or more, 80° or more, or 90° or more. There is no desired upper limit to the improvement in receding contact angle, and the receding contact angle can be as high as 180°. The receding contact angle can be measured by a variety of known methods. For example, the receding contact angle can be measured using a contact angle meter, such as that described in Example 1.

[0042] In one embodiment, the porous material having a patterned surface with a plurality of raised structures exhibits a desired sliding angle when contacted with a liquid contaminant. The sliding angle may be 75° or less, 60° or less, 40° or less, 30° or less, or 20° or less. For efficient removal of contaminants, the lowest possible sliding angle is desired. In practice, however, the sliding angle may be 1° or more, 2° or more, or 5° or more. The sliding angle may be in the range of 2° to 45°, 5° to 35°, or 5° to 20°. The sliding angle may be measured using a contact angle meter, for example, as described in Example 1.

[0043] Figure 3C is an image of an array of square shaped structures and Figure 3D is an image of an array of hexagonal shaped structures on a porous material. As can be seen in Figures 3C and 3D, the size of each structure and the pitch of each pattern varies the ratio of the raised surface area of ​​the pattern compared to the total patterned area.

[0044] 4A and 4B show the difference in pattern solid fraction between two raised structure arrays with different pattern pitches. Pattern solid fraction is defined as the ratio of the projected surface area to the unit area of ​​the pattern on the material. For example, Equation 2 above allows the calculation of the pattern solid fraction for a pattern with square-shaped structures. In FIGS. 4A and 4B, the total surface area of ​​the array and the size of the structures are the same, but the pitch of the structures is different. In FIG. 4A, the larger pitch p1 results in fewer structures 504 per unit area, resulting in a pattern solid fraction of about 0.25. In FIG. 4B, the smaller pitch p2 results in more structures 604 per the same total area, resulting in a higher pattern solid fraction of about 0.5. It has been shown that the pattern solid fraction of a raised pattern on a porous material affects the contact angle of a liquid droplet on the material.

[0045] FIG. 5A is a graph showing calculated and experimental contact angles as a function of pattern entity fraction of a porous material substrate. The graph shows that the experimental contact angles are predictable based on the Cassie-Baxter equation listed above. A contact angle is the angle measured through a liquid drop when a liquid-gas interface is in contact with a solid surface. Hydrophobic and oleophobic materials are defined as materials with contact angles greater than 90°, and superhydrophobic materials have contact angles greater than 150°. As can be seen, unpatterned materials and materials with a pattern entity fraction of 0.1 have lower contact angles. However, forming pattern entity fractions of 0.5 and 0.25 results in contact angles in the superhydrophobic range.

[0046] The results in Figure 5A are consistent with the calculated change in contact angle using the Cassie-Baxter equation described above. Table 1 shows the predicted change in contact angle between an unpatterned material and the same material after forming a raised structured pattern as described herein. The pattern has square shaped structures (s = 25 μm) with varying pitch (p) between them, thereby varying the pattern entity fraction (φ s ) varies. As seen in Table 1 below, a pattern entity fraction of 0.1 gives the highest contact angle; however, the pitch (p) may exceed the dimensions calculated in Equation 3 and the liquid will wet the raised structures. In this case, the droplet is not in the Cassie state and the sliding angle and rejection of contaminants are not likely to be improved compared to unpatterned material. This is also observed in FIG. 5A with a pattern entity fraction of 0.1, where a reduction in contact angle is observed compared to the other entity fraction patterns.

[0047] [Table 1]

[0048] The raised structures have a cross-sectional dimension (e.g., width) and a distance (pitch) from adjacent raised structures. The raised structures can provide a patterned outer surface having a pattern entity fraction. The pattern entity fraction is the ratio of the area covered by the raised structures to the total area of ​​the layer, calculated, for example, by Equation 2. In some embodiments, the pattern entity fraction is greater than 0.1. The pattern entity fraction may be 0.15 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.4 or more, or 0.5 or more. The pattern entity fraction may be 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. In certain embodiments, the pattern entity fraction is 0.1-0.8, 0.2-0.75, or 0.25-0.75.

[0049] In one embodiment, a layer of porous material has a patterned outer surface having a plurality of raised structures disposed thereon. The raised structures can be formed by any suitable method, such as stamping, etching, singeing, casting, phase inversion micromolding, and the like. The raised structures can be in a regular pattern and have a pitch (center-to-center distance) of 1 μm or more, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 50 μm or more, or 100 μm or more. The raised structures may have a pitch of 200 μm or less, 150 μm or less, 100 μm or less, 75 μm or less, 50 μm or less, 40 μm or less, or 25 μm or less. The raised structures may have a pitch of 1 μm to 100 μm, or 5 μm to 50 μm.

[0050] The raised structures may have a width of 0.5 μm or more, 1 μm or more, 2 μm or more, 5 μm or more, or 10 μm or more. The raised structures may have a width of 60 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, or 1 μm or less.

[0051] The effect of material patterning on contact angle can be seen in Figures 5B and 5C. In Figure 5B, a droplet is shown on an unpatterned material, and in Figure 5C, a droplet of the same size and material is shown on a patterned material. The droplet in Figure 5C is more spherical in shape due to the patterning compared to that in Figure 5B, giving it a larger contact angle.

[0052] Another method to control the contact angle is to use hierarchically structured materials. These materials have very low (e.g., less than 0.25) solid fractions on their surfaces, providing improved slip and rejection performance. An example of a hierarchically structured material made with cellulose acetate is shown in the image in FIG. 6. The material is a phase-inverted cellulose acetate membrane with nanometer-scale spheres or nodules on micrometer-scale fibers. The smaller structures of the hierarchical structure increase the wetting pressure of the liquid by creating petal states, and the larger fibers provide support and / or can hold a higher overall air flow for the material. The two size systems have their own breakthrough pressures, with nanoscale nodules having a higher breakthrough pressure than the microfiber pores. This difference in breakthrough pressures can lead to petal states, where the larger pores are wetted by the liquid while the smaller pores are not. Without being bound by theory, it is believed that the nanoscale nodules help reduce the solid fraction and reduce contact with liquid.

[0053] In one embodiment, a layer of porous material has an exterior surface with a hierarchical pattern including a plurality of microscale features (e.g., nodules) and a plurality of raised macroscale features formed thereon. The terms "microscale" and "macroscale" are used herein to distinguish features that differ in size by at least an order of magnitude, where it is understood that the microscale is smaller than the macroscale. The terms "microscale" and "macroscale" do not necessarily represent any particular size range. The material may further include features of intermediate feature sizes between the microscale and macroscale features, or features that are either smaller than the microscale features and larger than the macroscale features. In some cases, both microscale and macroscale features are formed during the fabrication of the porous material. In other cases, the microscale features are formed during the fabrication of the porous material, and the macroscale features are formed on the material (e.g., imprinted thereon) after the material is formed. In some embodiments, the porous material itself has a hierarchical structure, and another layer of hierarchical structure is added to the porous material in the form of raised macro-scale features. For example, cellulose acetate may have nodules of about 50 nm to 1000 nm in size and pores of about 0.2 μm to 20 μm (or even up to 50 μm in some cases), and raised structures may be formed on the cellulose acetate with sizes up to 60 μm. Thus, in some embodiments, the layer of porous material having a patterned outer surface contains two or more distinct levels of hierarchical structure. In some embodiments, the layer of porous material having a patterned outer surface contains three levels of hierarchical structure.

[0054] As discussed above, if liquid is not released or drained off of a porous material, it can block pores and cause airflow redirection. Rejection is defined as when the receding contact line (i.e., the back of the droplet) begins to move. A higher receding contact angle correlates with better rejection of contaminants. It has been found that hierarchically structured porous materials, when coated (e.g., with fluoropolymers), have low sliding angles (e.g., less than 20°) with water-based contaminants. However, when the hierarchically structured material is coated and patterned, it exhibits very low sliding angles (e.g., less than 10°) and high receding contact angles with a variety of liquids (with a variety of surface tensions), including some oils. Figure 7 is a graph showing contact angles of liquids with various surface tensions as a function of surface tension for various contact angles (static, advancing, and receding) on ​​patterned and unpatterned cellulose acetate. As can be seen in the graph, patterning the material surface has a particularly strong effect on the receding contact angle, meaning that patterning can be particularly useful for the release and drainage of liquids from porous materials.

[0055] A larger receding contact angle indicates that the patterned material clears the liquid, whereas the unpatterned material leaves behind a droplet. Traces or residual films can also block the pores of the material and reduce and / or redirect airflow. Without being bound by theory, it is believed that the larger receding contact angle may be due to the reduced solid fraction that occurs with patterning.

[0056] FIG. 8A is a graph showing the transmittance recovery performance of patterned and unpatterned cellulose acetate substrates after contamination with gear oil. The graph shows that the patterned material maintains a higher transmittance after contamination. FIGS. 8B and 8C show unpatterned and patterned materials after contamination with gear oil, where FIG. 8C is the hierarchical material with the pattern applied to FIG. 8B. FIG. 8B shows the unpatterned film with a thick oil film on the surface, while FIG. 8C shows only a few oil droplets on the pattern structure. The positioning of the oil on top of the pattern in FIG. 8C shows that the pattern achieves the Cassie state as discussed above, improving slide-off and rejection performance.

[0057] Hierarchical structures can be formed, for example, by phase inversion processes or by other methods, such as electrospun fibers. For example, hierarchical structures can be formed by including particulate matter in the polymer solution during electrospinning. The structures can also be achieved using coatings, where the hierarchical structures are introduced to the porous material in the coating and do not need to be part of the underlying material. Furthermore, hierarchical structures and raised patterns can be formed by phase inversion micromolding. The process involves first casting a polymer solution (containing a polymer dissolved in a solvent) onto a patterned substrate, then immersing the cast polymer in a bath of a non-solvent or using vapor induced phase separation to complete the phase inversion process. Once the polymer film is formed, it can be peeled off the patterned substrate, and a negative pattern is retained on the surface of the polymer film. In addition to the presence of a pattern increasing the contact angle and thus improving the hydrophobicity and / or oleophobicity, the dimensions of the pattern also have an effect.

[0058] While the above formulas are described as being used to determine the dimensions of the pattern applied to an existing porous material, the same formulas can also be used to directly form a pattern on the surface of a membrane as the membrane is produced. For example, the inherent pore structure of a phase inverted membrane can be designed according to the above formulas to provide raised structures without using a patterned substrate. Thus, hierarchical structures (or other porous materials) can be designed and formed with a predetermined height and / or spacing of raised structures when the material or coating is made. Techniques such as micromolding allow the pattern to be applied without reducing the transparency, and direct molding techniques reduce the number of steps / processes to arrive at a patterned substrate.

[0059] FIG. 9A is an image of a patterned porous material having a predetermined structure height and spacing, according to various embodiments described herein. The pattern includes raised lines 902 separated by spacing 904. The lines are approximately the same length and maintain a regular pitch throughout the pattern. FIG. 9B is a measured profile of the pattern of FIG. 9A. The height of the raised lines 902 is indicated by arrow hc, the width of the raised lines 902 is indicated by arrow w, and the spacing between the raised lines 902 is indicated by arrow d. The raised lines 902 have a width of about 25 μm, and the spacing between the raised lines 902 is about 25 μm. For example, control of structure height and spacing for a pattern is shown in FIG. 9A to control the sliding angle for a predicted contaminant on a known porous material.

[0060] 10 is a graph showing the sliding angle as a function of the height of a raised feature on a porous material. The shaded area 1002 shows the calculated predetermined height for the porous material and liquid contaminant as determined by Equation 1 above. As can be seen in the graph, each of the features having a structural height higher than the shaded area 1002 has a lower sliding angle than the unpatterned material 1004 and the material having a structural height lower than the predetermined height 1006.

[0061] FIG. 11 is a graph showing the sliding angle of liquids with various surface tensions as a function of surface tension for an unpatterned material, as well as the same material with large (50 μm) and small (10 μm) pattern spacing. As can be seen in the graph, patterning the surface (regardless of spacing size) reduces the sliding angle for liquids at all surface tensions. However, for low surface tension liquids, a narrower pattern spacing reduces the sliding angle. Thus, both the pattern height and spacing can be used to control the sliding angle of a material.

[0062] The layer of porous material having a patterned outer surface with a plurality of raised structures can be manufactured from a variety of suitable materials. Examples of materials that can be used to make the porous material include fibrous materials (e.g., woven filtration media, nonwoven filtration media made from fibers, aligned electrospun fibers, etc.), membranes, aperture films, laminated membranes, etc. Fibrous materials include polymeric fibers, glass fibers, and metal fibers. Examples of typical polymers used in filtration media include polypropylene, polyethylene, polyester, polysulfone, polyethersulfone, expanded polytetrafluoroethylene ("ePTFE"), polyvinylidene fluoride, polyamide (nylon), polyacrylonitrile, polycarbonate, cellulose acetate, cellulose, etc., and combinations thereof. Examples of typical polymers used as membranes include: ePTFE, polypropylene, polyethylene, polyester, polysulfone, polyethersulfone, polyvinylidene fluoride, polyamide (nylon), polyacrylonitrile, polycarbonate, cellulose acetate, and combinations thereof. The material can be selected based on the intended use of the porous patterned material and the method used to impart a pattern of raised structures onto the material. Various methods for imparting a pattern of raised structures onto a material include: stamping, etching, singeing, casting, phase inversion micromolding, etc. Stamping is particularly suitable for patterning thermoplastics and other compressible porous materials.

[0063] In addition to controlling the height and spacing of the raised patterns on the porous material, the material can also be coated to further improve its sliding angle. Figure 12 is a graph showing the sliding angle of liquids with various surface tensions as a function of surface tension for unpatterned and uncoated, unpatterned but coated, and patterned and coated materials. It can be seen that patterning and coating the material reduces the sliding angle for the same material across all surface tensions, especially above 30 mN / m. Again, at higher surface tensions, the patterned and coated material has a significantly lower sliding angle than the unpatterned substrate, and at lower surface tensions (<30 mN / m), the patterned material has a similar sliding angle to the unpatterned substrate. At the two lowest surface tensions, the liquid completely wets the unpatterned and uncoated material, as indicated by the 90° sliding angle, suggesting that the liquid will not slide off even if the material is held vertically. As the pattern spacing is narrowed (i.e., P wet ) the sliding angle at these two data points at the lowest surface tension for the patterned and coated material will be similarly small.

[0064] Patterning a porous material surface via imprinting can also reduce the permeability of the material due to compression of the surface. Figure 13A is a graph showing the loss of permeability as a function of imprint pressure at low (room temperature) and high (100°C) imprint temperatures for a low porosity material, and Figure 13B is a graph showing the loss of permeability as a function of pressure at low and high temperatures for a high porosity material. The Frazier permeability of each membrane was measured, which measures the volume of air that passes through a given area of ​​a porous material. Frazier permeability can be measured using known methods, such as ASTM D737-18. In this case, the measurement was made at 0.6 in 2 Frazier permeability is typically measured in cfm / ft2 at 0.5 inches of water pressure differential. 2 (1 cfm / ft2 at 0.5 inches of water pressure) 2 is 0.5 cm at 125 Pa 3 / s / cm 2 (corresponding to 0.05 cfm / ft 2 at 0.5 inch water column differential). In this specification, all Frazier permeability readings are taken at 0.5 inch water column differential. High porosity materials generally have high Frazier permeability and low porosity materials generally have low Frazier permeability. When patterns are formed at high temperatures, the drop in permeability is fairly consistent for both low and high porosity materials. As expected, when formed at low pressure and low temperature, the drop in permeability is much smaller or negligible. However, the dimensions of the patterns formed vary depending on the pressure and temperature. Generally, higher pressures and / or temperatures can be used to form patterns with higher features. Thus, by selecting a pressure and temperature range, it is possible to obtain pattern heights greater than the minimum height calculated from Equation 1 without significantly sacrificing permeability. For example, it may be desirable to determine, prior to patterning, that the material has a pore size of at least about 0.05 μm and a permeability of 0.05 cfm / ft 2 at 0.5 inch water column differential. 2 (0.025 cm at 125 Pa) 3 / s / cm2 After compression or patterning, the material has a Frazier permeability of at least 0.05 cfm / ft 2 (0.025 cm at 125 Pa) 3 / s / cm 2 Materials patterned as described herein can have a Frazier transparency of at least 10%, or at least 30%, or at least 50% of the transparency of an otherwise identical unpatterned layer.

[0065] In one embodiment, the porous material has a patterned outer surface having a plurality of raised structures disposed on the outer surface, and has a flow rate of 0.1 cfm / ft 2 (0.051 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.2cfm / ft 2 (0.10 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.4 cfm / ft 2 (0.20 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.5 cfm / ft 2 (0.25 cm at 125 Pa 3 / s / cm 2 ) or more, 0.6 cfm / ft 2 (0.30 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.7cfm / ft 2 (0.36 cm at 125 Pa 3 / s / cm 2 ) or more, 0.8 cfm / ft 2 (0.41 cm at 125 Pa 3 / s / cm 2 ) or more, 0.9 cfm / ft 2 (0.46 cm at 125 Pa 3 / s / cm 2 ) or more than 1 cfm / ft 2 (0.51 cm at 125 Pa 3 / s / cm 2) or greater. In practice, there is no desired upper limit to the permeability of the material, but it is preferred that the Frazier permeability of the patterned material be greater than or equal to 3 cfm / ft 2 (1.52 cm at 125 Pa 3 / s / cm 2 ) or less, 2.5cfm / ft 2 (1.27 cm at 125 Pa 3 / s / cm 2 ) or less, or 2 cfm / ft 2 (1.02 cm at 125 Pa 3 / s / cm 2 ) or less.

[0066] In certain embodiments, the loss of permeability can be reduced or avoided by using a patterned porous material of a composite material. The composite material can be a multi-layer material. The outermost layer of the composite material can be patterned as described herein.

[0067] 14A and 14B show a composite or multi-layer material in which a patterned layer is combined with an underlying porous material layer. Providing a patterned layer on the underlying porous material layer allows the patterned structure to be assembled without reducing the permeability of the underlying porous material and allows the original permeability and water entry pressure specifications of the porous material for a particular application to be maintained.

[0068] In FIG. 14A, a first layer of porous material is 1402. A second layer of material 1404 is disposed on and / or combined with the first layer to form a two-layer composite. A pattern is formed in the second layer to provide the advantages discussed herein of low sliding angle and improved contaminant rejection. The pattern may be formed on the second layer prior to combining the layers to form the composite, or after the first and second layers are bonded together. Alternatively, the pattern may be formed on the second layer after combining the layers. The first layer is a ready-to-use porous material designed to meet the air flow and water inlet pressure specifications required for the desired use (e.g., degassing). The second, structured layer is designed for one or more anticipated contaminants in the desired use to provide a low sliding angle and a high receding contact angle (i.e., improved rejection). Without the second, patterned layer of material, the porous material would not be able to easily eliminate contaminants, resulting in liquids blocking the pores and reducing airflow. The second, patterned layer may also be a porous material, either the same material as the first layer or a different type of porous material.

[0069] In certain embodiments, the second, patterned material may include at least one of a polymer fiber, a metal mesh, expanded polytetrafluoroethylene ("ePTFE"), a laser etched material, or other polymer material. The polymer fiber may be of any suitable shape or form, such as a cylindrical fiber, a square fiber, or a concave cross-section.

[0070] The composite material can be formed by laminating two layers of material together or by a combination of various methods. The pattern in the second layer can also be formed by a combination of various methods. For example, FIG. 14A shows a second layer with an imprinted pattern that includes a residual thickness 1406 of the second layer between the bottom of the structure and the upper surface of the first layer. FIG. 14B shows another embodiment where the patterned second layer does not include a residual thickness. The pattern in the embodiment of FIG. 14B can be formed by a variety of techniques, including etching, singeing, fiber deposition, and porous material stretching (e.g., to form an apertured membrane).

[0071] The composite material can include a wide variety of combinations of materials. Suitable materials for the first layer include polypropylene, polyethylene, polyester, polysulfone, polyethersulfone, expanded polytetrafluoroethylene ("ePTFE"), polyvinylidene fluoride, polyamide (nylon), polyacrylonitrile, polycarbonate, cellulose acetate, and combinations thereof. Suitable materials for the second layer include any suitable filtration media, such as media prepared from polymeric fibers, metal mesh, expanded polytetrafluoroethylene ("ePTFE"), laser etched materials, or other polymeric materials. The first and second layers may be prepared separately and combined (e.g., laminated) to form the composite material. Alternatively, the first or second layer may be prepared (e.g., cast) directly on the other layer. The second (patterned) layer may be patterned before or after combination with the first layer. In some embodiments, both layers comprise ePTFE but have different molecular weights (e.g., a low and a high molecular weight resin), where the low molecular weight resin does not stretch as much as the high molecular weight resin, but is still high enough not to burst upon expansion, providing a unique pattern.

[0072] In certain embodiments, the second, patterned layer may be prepared from a material with high pore / permeability (e.g., 4 times the desired permeability / pore size) to accommodate the expected drop in permeability after imprinting the pattern. Such a layer may be expanded polytetrafluoroethylene. The second layer may have a thickness of at least 20-30 μm. The second layer may be combined with a non-patterned layer of expanded polytetrafluoroethylene.

[0073] In certain embodiments, the composite material may include an asymmetric expanded polytetrafluoroethylene structure (e.g., having regions of the material with different properties, such as pore size). In some embodiments, one of the layers may be a stretched extrudate laminated onto an unstretched extrudate. The layers may then be further stretched together.

[0074] In some embodiments, the second layer includes a material with an open structure having aligned (anisotropic) nodes to provide higher transparency.

[0075] In one embodiment, the material of the second layer is compressible to allow for imprinting of the raised pattern structure. The loss of some pore structure can be compensated for by choosing a more open pore structure in the layer before patterning. It is preferred that the material is not compressible enough to lose pore structure during imprinting, so that a very open initial pore structure is not required before patterning. Generally, a material with high air flow and good compressibility will be patterned as the second layer. In some embodiments, the second layer is prepared from a material with many nodes and fibrils. The nodes can be compressed to form the pattern of the second layer, but by avoiding the compression of the fibrils / pores, a loss of permeability is prevented. In a further embodiment, the second layer is prepared from uniaxially expanded polytetrafluoroethylene, which may have a weaker structure than the uniaxially expanded polytetrafluoroethylene underneath.

[0076] The pattern of the second layer is designed to provide the desired slide angle and rejection performance with the liquid contaminants envisioned herein. Both the material properties (including porosity and structure) and the pattern of the second layer, as well as the surface tension of the contaminants envisioned, are design considerations. Although the composite material has been described as a two-layer material, the composite material may include three or more layers. The composite material may further include two or more patterned surfaces. In some embodiments, the porous material may be patterned on opposing surfaces, either directly on one surface with a patterned material combined with the other, or with two patterned layers combined on both sides of the porous material.

[0077] Below, methods for forming patterned surfaces are described.

[0078] Turning to FIG. 15, a method for forming a patterned porous material, either directly on the outer surface of a material or as a composite material as previously described, is shown. A stamp 1502 is created or prepared for imprinting a layer of porous material or a layer to be combined with a layer of porous material. The stamp 1502 may be formed from a rigid material (e.g., a silicon wafer) that has been patterned, for example, via photolithography, and includes one or more raised regions 1504 and one or more gaps 1506 adjacent or between the raised regions 1504. The raised regions 1504 and gaps 1506 form a negative pattern that corresponds to a desired pattern in the porous material. The desired pattern includes at least structures having a predetermined height and a predetermined pitch or spacing, as previously described. Because the dimensions of the pattern structures are typically on the nanometer or micrometer scale, the production process can also be referred to as nanoimprint lithography. Gaps 1506 are formed on the stamp 1502 to correspond to the desired shape and desired height of the resulting structures 1512 in the porous material pattern, with protruding areas 1504 forming spaces 1514 and defining the spacing between the resulting structures. A layer of porous material 1508, i.e., the layer of material to be patterned and combined with the porous material, is provided alone or on a support structure 1510, depending on the strength and other properties of the layer 1508 to be patterned. The support structure 1510 may be formed of any material that can withstand the imprinting environmental conditions. Examples of suitable support structure materials include: polytetrafluoroethylene, other fluoropolymers, silicone-based materials, or other inert materials that do not deform at the imprinting temperatures.

[0079] The stamp 1502 is contacted with the surface of the material 1508 to be patterned by applying pressure and / or temperature for a predetermined time. The pressure and / or temperature conditions can be based on the material to be patterned as well as the desired pattern design. For example, the applied pressure can be 0.3 bar or more, 2 bar or more, 5 bar or more, or 10 bar or more. The applied pressure can be 50 bar or less, 40 bar or less, or 30 bar or less. In some embodiments, the applied pressure is in the range of 0.3 bar to 50 bar, or 5 bar to 40 bar. The applied temperature can be room temperature or more, 30° C. or more, 60° C. or more, or 100° C. or more. The applied temperature can be 250° C. or less, 200° C. or less, or 150° C. or less. The applied temperature can be in the range of 60° C. to 250° C., or 100° C. to 200° C. If both temperature and pressure are applied, temperature may be applied in the imprinting environment (e.g., in a heated chamber) or directly through the stamp 1502. The temperature and / or pressure may be applied for a predetermined time, e.g., ranging from about 1 second up to 10 minutes. When the stamp 1502 and patterned material 1508 are separated (e.g., after the temperature of the material has cooled to at least below the Tg of the polymer, preferably below 40° C.), the resulting surface of the patterned material 1508 contains a pattern of structures 1512 having a predetermined height and a predetermined spacing. The predetermined height is measured from the lowest point of the space 1514 between the structures to the outermost (highest) of the patterned layer. When a pattern is imprinted onto the material, there may be a residual thickness 1515 between the opposite surface of the material layer (i.e., the unpatterned surface) and the lowest point of the pattern spacing.

[0080] A stamp 1502 can be used to imprint a predetermined area on the surface of the layer. If a larger pattern is desired, the stamp can be applied to another (immediately adjacent or distant) portion of the layer of material.

[0081] Another method of imprinting is shown in Figures 16A and 16B. In Figure 16A, the stamp 1602 is in the form of an embossed roller or wheel. The embossed roller 1602 further includes one or more raised areas 1604 and one or more gaps 1606 adjacent to or between the raised areas 1604. The raised areas 1604 and gaps 1606 again form a negative pattern that corresponds to the desired pattern in the material 1608 to be patterned. The raised areas 1604 and / or gaps 1606 may have uniform dimensions around the circumference of the embossed roller 1602 or may vary in one or more dimensions. The porous or other material 1608 to be patterned is fed to the stamp substantially continuously, for example, in a roll-to-roll process. However, the rate at which the porous material is fed to the embossed roller 1602 can be varied. Depending on the strength and other properties of the layer 1608 to be patterned, the layer 1608 of material on the support structure 1610 may be fed to the embossed roller 1602 as previously described. In an alternative embodiment, the imprinting may be performed by a roll-to-plate process.

[0082] If a single surface of the porous material 1608 is to be patterned, a non-patterned, hard roller 1618 may be provided opposite the embossed roller 1602 to control the imprinting conditions. For example, the distance between the non-patterned roller 1618 and the embossed roller 1602 may determine the pressure applied to the layer of material 1608 fed to the embossed roller 1602. Additionally, one or more of the non-patterned roller 1618, the embossed roller 1602, or the atmosphere (e.g., an enclosed, chamber environment) may be heated to apply temperature during imprinting. Although shown in cross section, the embossed roller 1602 may have various lengths corresponding to the width of the layer of material fed to the embossed roller 1602, or the length may be longer or shorter than the width of the feed material 1608. When the patterned material 1608 leaves the embossed roller 1602, the surface of the resulting patterned material 1608 includes a pattern of structures 1612 having a predetermined height and a predetermined pitch or spacing 1614.

[0083] In FIG. 16B, an embossed roller 1602A is positioned opposite a second embossed roller 1602B to impart a pattern to both sides of the porous material 1608. Both embossed rollers 1602A and 1602B are in the form of wheels. Each of the embossed rollers 1602A,B includes one or more raised areas 1604A,B and one or more gaps 1606A,B adjacent to or between the raised areas 1604A,B. As previously described, the raised areas 1604A,B and / or gaps 1606A,B may have uniform dimensions around the circumference of the respective stamps 1602A,B, or may vary in one or more dimensions. The raised areas 1604A,B and gaps 1606A,B form a negative pattern that corresponds to the desired pattern on each surface of the porous material 1608. The desired pattern includes structures 1612A, B having at least a predetermined height and at least a predetermined pitch or spacing 1614 A, B. Each pattern on the embossed roller 1602 A, B may be the same or they may be different.

[0084] If the patterns are the same, the embossed rollers 1602A,B may be positioned in an offset fashion such that the pattern structure 1612A on one side of the patterned porous material 1608 is located opposite the pattern spacing 1614B on the other side of the porous material 1608. The porous material 1608 is further fed to the embossed rollers 1602A,B substantially continuously, for example, in a roll-to-roll process. However, the speed at which the porous material is fed to the embossed rollers 1602A,B may be varied. Once the porous material has a patterned surface (either directly or in combination with a patterned material layer) with a predetermined height and spacing, the material is ready for use. However, in certain embodiments, a coating is applied to the material prior to use.

[0085] Alternatively, it is possible to produce a material having a patterned surface on both major sides by laminating two patterned layers together. The resulting laminated patterned porous material contains a plurality of raised structures on both major sides of the material. The sides may be identical or similar, or may be different from each other, for example, having a different chemical composition or patterning.

[0086] In some embodiments, the patterned material (e.g., the second layer) may be prepared by a phase inversion micromolding process. Phase inversion micromolding involves casting a polymer solution onto a patterned substrate and subjecting the cast polymer solution to a phase inversion process to form a film. The formed film is then peeled off the patterned substrate. The process may also be performed as a roll-to-roll process with the patterned substrate.

[0087] In one embodiment, a polymer solution is cast onto a patterned substrate to prepare a film having a first thickness. A blade can be passed over the film at a certain height to remove some of the polymer solution to a second height. The film can be treated (e.g., immersed) in a solvent (e.g., water) in which the polymer is insoluble.

[0088] The phase inversion microformed membrane can be created or added onto a support layer or substrate. The support layer or substrate may form the first layer or material, or the phase inversion microformed membrane may be further transferred from the support layer or substrate to another layer (e.g., the first layer). In some cases, the support layer or substrate is an ePTFE membrane.

[0089] Phase inversion micromolding can also be used to form hierarchical structures, where the phase inversion process creates microscale structures while the mold creates macroscale structures. The microscale structures can include multiple nodules and highly porous structures that extend throughout the layer. Nodule formation is further promoted by increasing the vapor exchange time during phase inversion.

[0090] In some embodiments, the polymer solution is cast onto a mold (e.g., a wafer) and the support layer or substrate is laminated onto the polymer solution. In some cases, the patterned mold may be prepared for casting by plasma cleaning. In some cases, after casting, the material is subjected to a vacuum treatment to remove excess air bubbles.

[0091] Examples of polymers for phase inversion micromolding include polymers that are soluble in one solvent and precipitate in another, such as polypropylene, polyethylene, polyester, polysulfone, polyethersulfone, polyvinylpyrrolidone, polyvinylidene fluoride, polyamide (nylon), polyacrylonitrile, polycarbonate, cellulose acetate, and combinations thereof. Preferred polymers include, for example, polyethersulfone, polysulfone, polyvinylidene fluoride, and cellulose acetate.

[0092] In one embodiment, a material produced by a phase inversion process and having both microscale and macroscale structures has a flow rate of 0.1 cfm / ft 2 (0.051 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.2cfm / ft 2 (0.10 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.4 cfm / ft 2 (0.20 cm at 125 Pa) 3 / s / cm2 ) or more, 0.5 cfm / ft 2 (0.25 cm at 125 Pa 3 / s / cm 2 ) or more, 0.6 cfm / ft 2 (0.30 cm at 125 Pa) 3 / s / cm 2 ) or more, 0.7cfm / ft 2 (0.36 cm at 125 Pa 3 / s / cm 2 ) or more, 0.8 cfm / ft 2 (0.41 cm at 125 Pa 3 / s / cm 2 ) or more, 0.9 cfm / ft 2 (0.46 cm at 125 Pa 3 / s / cm 2 ) or more than 1 cfm / ft 2 (0.51 cm at 125 Pa 3 / s / cm 2 ) or greater. In practice, there is no desired upper limit to the permeability of the material, but it is preferred that the Frazier permeability of the patterned material be greater than or equal to 3 cfm / ft 2 (1.52 cm at 125 Pa 3 / s / cm 2 ) or less, 2.5cfm / ft 2 (1.27 cm at 125 Pa 3 / s / cm 2 ) or less, or 2 cfm / ft 2 (1.02 cm at 125 Pa 3 / s / cm 2 ) or less.

[0093] The contact angle of the liquid on the material depends on the liquid used in the test as well as the nature of the material. In some embodiments, materials made by phase inversion micromolding from polyethersulfone exhibit contact angles of 75° or more, 80° or more, 85° or more, or 90° or more when tested using KAYDOL mineral oil. In some embodiments, materials made by phase inversion micromolding from polyethersulfone exhibit slide angles of 35° or less, 33° or less, 30° or less, or 25° or less.

[0094] One advantage of phase inversion is that micromolded materials experience more limited loss of permeability compared to imprinted patterns. Films prepared by phase inversion micromolding can shrink when formed (e.g., when the solvent is removed). This results in stretching and enlargement of the pores between the pattern features. This improves permeability and maintains permeability when the film comes into contact with contaminants. Phase inversion micromolding can also be used to create pattern structures with more defined (e.g., sharper) corners and taller features, which further improves liquid-phobicity.

[0095] FIG. 17 is a schematic cross-sectional view of a patterned porous material 1702 including a coating 1710. The coating may be applied to the outer surface of the patterned porous material 1702, including the tops of one or more of the structures 1704, the bottoms of the spaces between the structures 1706, and the sides of the structures 1708. The coating may be applied before or after the pattern is formed on the porous material. The coating may be applied to improve the oleophobicity of the porous material. Examples of coatings include fluoropolymer or perfluoropolyether (PFPE) bottlebrush polymers, including those described in U.S. Provisional Patent Application No. 63 / 067,053, filed Aug. 18, 2020, and U.S. Provisional Patent Application No. 63 / 185,084, filed Feb. 3, 2021, both of which are incorporated herein by reference. In certain embodiments, the coating may be or include a fluoropolymer including poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) or poly(2,2,3,3,4,4,4-heptafluorobutyl acrylate).

[0096] As noted above, by controlling the height and pitch or spacing of the structures, structured patterns can be designed to improve the hydrophobicity and / or oleophobicity of the filtration media material or degassing media with respect to anticipated contaminants. Patterned filtration media, with or without coatings, can improve performance and life in degassing applications where the filtration media is exposed to potential liquid contaminants that are difficult to remove from the filtration media surface. Improved removal performance allows for the reduction or elimination of environmentally unfriendly, biopersistent chemical coatings.

[0097] In general, the venting media of the present disclosure can be used in a variety of venting applications. A schematic diagram of a typical venting device 2800 is shown in FIG. 18. The venting device 2800 includes an opening (vent) 2802 to allow air to vent to the environment. The opening 2802 is blocked with a patterned porous material 1802. The patterned porous material 1802 includes a layer of porous material including a plurality of raised structures disposed on a surface of the layer, as described herein. The patterned porous material 1802 may optionally be coated with a coating. The patterned porous material 1802 may be attached to the venting device 2800 by a suitable attachment 2804, such as, for example, an adhesive, heat bonding, ultrasonic bonding, over molding, interference fit, and the like.

[0098] In one embodiment, the degassing media of the present disclosure is used in degassing applications for battery packs, such as battery packs used in electric vehicles. The battery pack is surrounded by an enclosure filled with air or an active cooling fluid, such as oil. Specifically, a thermally runaway-prone lithium-ion battery is surrounded by cooling oil to cool the battery. If the pack is surrounded by oil, the oil may come into contact with the battery pack's vent, resulting in filming over and reducing the permeability of the vent. In one embodiment, the battery pack's vent includes the degassing media of the present disclosure. By using the degassing media of the present disclosure, the oil is quickly drained, preventing filming over and allowing the vent to regain its permeability. In one embodiment, as seen in FIG. 19, a battery pack 2900 includes one or more batteries 2910 disposed within an enclosure 2920, and cooling oil 2930 at least partially surrounding the one or more batteries 2910. The battery 2910 may be a lithium ion battery. The enclosure 2920 includes one or more venting ports 2922 that are plugged with a degassing medium 2902. In some embodiments, the degassing medium 2902 is or includes a patterned cellulose acetate medium. In some embodiments, the degassing medium 2902 is coated.

[0099] In one embodiment, the degassing media of the present disclosure is used in degassing applications for filled materials. Many packaging degassing applications use degassing due to pressure and / or temperature changes during shipping or storage. For example, liquid products may shift inside the package during shipping or handling, or the package may be turned over and liquid products inside the package may cause contamination of the degassing surface. In one embodiment, the degassing of the package includes the degassing media of the present disclosure. By using the degassing media of the present disclosure, liquids may be quickly evacuated to avoid skinning, and the degassing may restore the permeability to allow continued air flow when the bottle is erected or splashed. Furthermore, when the degassing port is contacted with liquid (e.g., when the package is turned over), the degassing media (especially coated degassing media) may increase the intrusion pressure and prevent liquid from leaking through the degassing port. The venting opening may be located in the main body of the package or in a lid, cap, or insert. In one embodiment, as seen in Figures 20A-20C, a package 3900 (e.g., a cap or insert) includes one or more venting openings 3922 that are blocked with a venting medium 3902. The venting medium 3902 may be attached in a variety of ways, on or over the venting opening 3922, or in a variety of locations, as seen in Figures 20A-20C and 21A-21C. The venting medium may be attached by any suitable attachment, such as, for example, by adhesive, heat bonding, ultrasonic bonding, overmolding, interference fit, and the like. In Figures 21A-21C, the venting medium is attached by a fusion bond 3908. In some embodiments, the venting medium 3902 is or includes a patterned cellulose acetate medium. In some embodiments, the venting medium 3902 is coated.

[0100] Illustrative Embodiments The technology described herein is defined in the claims. However, below we provide a non-limiting list of non-limiting embodiments, any one or more of which may be combined with one or more of the other examples, embodiments, or aspects described herein.

[0101] Embodiment 1 is a filtration medium comprising a layer of porous material having a patterned outer surface including a plurality of pillars, wherein each pillar in the plurality has a height that is predetermined based at least on an expected contaminant, and wherein the spacing between each pillar in a pair of the plurality of pillars is at most the spacing that is predetermined based on the expected contaminant.

[0102] Embodiment 2 is the filtration medium according to any one of embodiments 1 and 3 to 13, wherein the porous material is a membrane.

[0103] Embodiment 3 is the filtration medium according to any one of embodiments 1-2 and 4-13, wherein the membrane comprises one of polypropylene, polyethylene, polyester, polyethersulfone, polysulfone, expanded polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyacrylonitrile, polycarbonate, and cellulose acetate.

[0104] Embodiment 4 is the filtration medium according to any one of embodiments 1 to 3 and 5 to 13, wherein the predetermined height is:

number

[0105] Embodiment 5 is the filtration medium according to any one of embodiments 1 to 4 and 6 to 13, wherein the predetermined interval is:

number

[0106] Embodiment 6 is a filtration medium according to any one of embodiments 1 to 5 and 7 to 13, wherein the predetermined height and predetermined spacing provide a sliding angle in the range of 0 to 20 for a 20 microliter droplet of a potential contaminant having a surface tension of 72 mN / m or less.

[0107] Embodiment 7 is a filtration medium according to any one of embodiments 1 to 6 and 8 to 13, wherein the patterned layer of porous material has a sliding angle on a potential contaminant that is lower than the sliding angle on an otherwise identical unpatterned layer.

[0108] Embodiment 8 is the filtration medium of any one of embodiments 1 to 7 and 9 to 13, wherein the layer of porous material further comprises a coating that increases the oleophobicity of the layer.

[0109] Embodiment 9 is the filtration medium according to any one of embodiments 1 to 8 and 10 to 13, wherein the coating is a fluoropolymer comprising poly(2,2-3,3-4,4,4-heptafluorobutyl methacrylate) or poly(2,2-3,3-4-4-4-heptafluorobutyl acrylate).

[0110] Embodiment 10 is the filtration medium of any one of embodiments 1 to 9 and 11 to 13, wherein the coating comprises a perfluoropolyether (PFPE) bottle brush polymer.

[0111] Embodiment 11 is a filtration medium according to any one of embodiments 1 to 10 and 12 to 13, wherein the plurality of morphological pillars comprises an outer surface pattern substance fraction of 0.75 or less.

[0112] Embodiment 12 is the filtration medium of any one of embodiments 1 to 11 and 13, wherein the porous material has a pore size of at least 0.05 μm and a pore size of at least 0.05 cfm / ft before the exterior surface is patterned. 2 (0.025 cm at 125 Pa) 3 / s / cm 2 ) a filtration medium having a permeability of

[0113] Embodiment 13 is the filtration medium of any one of embodiments 1 to 12, wherein the patterned layer of porous material has a permeability that is at least 10% of the permeability of an otherwise identical unpatterned layer.

[0114] Embodiment 14 is a filtration medium comprising a layer of porous material having a patterned outer surface including a plurality of structures, wherein each structure in the plurality of configurations has a height that is at least predetermined based on an anticipated contaminant, and wherein a spacing between each structure in a pair of structures in the plurality of configurations is at most predetermined based on an anticipated contaminant.

[0115] Embodiment 15 is the filtration medium according to any one of embodiments 14 and 16 to 21, wherein the predetermined height is:

number

[0116] Embodiment 16 is the filtration medium according to any one of embodiments 14 to 15 and 17 to 21, wherein the predetermined interval is:

number

[0117] Embodiment 17 is a filtration medium described in any one of embodiments 14 to 16 and 18 to 21, wherein the predetermined height and predetermined spacing provide a sliding angle in the range of 0 to 20 for a 20 microliter droplet of a hypothetical contaminant having a surface tension of 72 mN / m or less.

[0118] Embodiment 18 is a filtration medium described in any one of embodiments 14 to 17 and 19 to 21, wherein the patterned layer of porous material has a sliding angle with the anticipated contaminant that is lower than the sliding angle with the anticipated contaminant of an otherwise identical layer of porous material that is not patterned.

[0119] Embodiment 19 is a filtration medium described in any one of embodiments 14 to 18 and 20 to 21, wherein the plurality of morphological structures comprises an outer surface pattern substance fraction of 0.75 or less.

[0120] Embodiment 20 is the filtration medium of any one of embodiments 14 to 19 and 21, wherein the patterned layer of porous material has a permeability that is at least 10% of the permeability of an otherwise identical unpatterned layer.

[0121] Embodiment 21 is the filtration medium according to any one of embodiments 14 to 20, wherein the predetermined height is less than 12 microns.

[0122] Embodiment 22 is a filtration medium comprising: a first layer of porous material; and a second layer of material disposed on the first layer, the second layer having a patterned outer surface comprising a plurality of structures, wherein each structure in the plurality of configurations has a height that is at least predetermined based on an anticipated contaminant, and wherein a spacing between each structure in a pair of the plurality of configurations is at most predetermined based on an anticipated contaminant.

[0123] Embodiment 23 is the filtration medium according to any one of embodiments 22 and 24 to 32, wherein the first layer and the second layer comprise the same material.

[0124] Embodiment 24 is the filtration medium of any one of embodiments 22-23 and 25-32, wherein the second layer comprises at least one of polymer fibers, metal mesh, expanded polytetrafluoroethylene, a phase inverted membrane, a particle-supported coating, and a laser etched material.

[0125] Embodiment 25 is the filtration medium according to any one of embodiments 22 to 24 and 26 to 32, wherein the second layer is laminated on the first layer.

[0126] Embodiment 26 is the filtration medium of any one of embodiments 22-25 and 27-32, wherein the first layer comprises expanded polytetrafluoroethylene having pores of a first size, and the second layer comprises expanded polytetrafluoroethylene having pores of a second, larger size.

[0127] Embodiment 27 is the filtration medium according to any one of embodiments 22 to 26 and 28 to 32, wherein the structures having a plurality of forms have a concave shape.

[0128] Embodiment 28 is the filtration medium of any one of embodiments 22 to 27 and 29 to 32, wherein the predetermined height is:

number

[0129] Embodiment 29 is the filtration medium according to any one of embodiments 22 to 28 and 30 to 32, wherein the predetermined interval is:

number

[0130] Embodiment 30 is the filtration medium of any one of embodiments 22 to 29 and 31 to 32, wherein the second layer further comprises a coating that improves the oleophobicity of the second layer.

[0131] Embodiment 31 is the filtration medium according to any one of embodiments 22 to 30 and 32, wherein the coating is a fluoropolymer comprising poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) or poly(2,2,3,3,4,4,4-heptafluorobutyl acrylate).

[0132] Embodiment 32 is a filtration medium described in any one of embodiments 22 to 31, wherein the coating comprises a perfluoropolyether (PFPE) bottle brush polymer.

[0133] Embodiment 33 is a filtration medium comprising a layer of porous material having a hierarchical structure and a patterned outer surface including a plurality of structures, wherein each structure in the plurality of configurations has a height that is at least predetermined based on an anticipated contaminant, and wherein the spacing between each structure in a pair of structures in the plurality of configurations is at most predetermined based on an anticipated contaminant.

[0134] Embodiment 34 is the filtration medium of any one of embodiments 33 and 35 to 39, wherein the predetermined height is:

number

[0135] Embodiment 35 is the filtration medium according to any one of embodiments 33 to 34 and 36 to 39, wherein the predetermined interval is:

number

[0136] Embodiment 36 is a filtration medium described in any one of embodiments 33 to 35 and 37 to 39, wherein the layer of porous material further comprises a coating that increases the oleophobicity of the second layer.

[0137] Embodiment 37 is the filtration medium according to any one of embodiments 33 to 36 and 38 to 39, wherein the porous material is a phase inversion material.

[0138] Embodiment 38 is the filtration medium of any one of embodiments 33 to 37 and 39, wherein the porous material comprises a particulate coating on a membrane comprising one of polypropylene, polyethylene, polyester, polyethersulfone, polysulfone, expanded polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyacrylonitrile, polycarbonate, and cellulose acetate.

[0139] Embodiment 39 is a filtration medium described in any one of embodiments 33 to 38, wherein the hierarchical structure of the porous material includes micro-scale features and macro-scale features, and the micro-scale features may include nodules.

[0140] Embodiment 40 is a venting device comprising an opening configured to vent an enclosed container, and a venting element secured within the venting device and forming a liquid-tight, gas-permeable seal at the opening, the venting element comprising a porous material having a patterned surface including a plurality of structures, wherein each structure in the plurality of configurations has a height that is at least predetermined based on an anticipated contaminant, and wherein a spacing between each structure in a pair of the plurality of configurations is at most predetermined based on an anticipated contaminant.

[0141] Embodiment 41 is a method comprising the steps of: providing a layer of porous material; providing a stamp having a patterned outer surface corresponding to a negative of a pattern including a plurality of structures, wherein each structure in the plurality of structures has at least a predetermined height based on anticipated contaminants, and wherein a spacing between each structure in a pair of the plurality of structures is at most a predetermined spacing based on anticipated contaminants; and applying the stamp to a first surface of a layer of porous material at a predetermined temperature and pressure to form the pattern of a plurality of structures having the predetermined height and spacing on the first surface of the layer of porous material; A method comprising:

[0142] Embodiment 42 is a method described in any one of embodiments 41 and 43 to 46, wherein the stamp is a circular stamp and the step of providing a layer of porous material includes providing a roll of porous material for forming a pattern of multiple structures in a roll-to-roll process or a roll-to-plate process.

[0143] Embodiment 43 is the method according to any one of embodiments 41 to 42 and 44 to 46, comprising the steps of providing a second stamp having a second patterned outer surface corresponding to a negative of a second pattern including a plurality of structures, wherein each structure in the plurality of features has at least a predetermined height based on anticipated contaminants and a spacing between each structure of a pair of the plurality of features is at most a predetermined spacing based on anticipated contaminants; and applying the second stamp to a second, opposing surface of the layer of porous material at a predetermined temperature and pressure to form the pattern of a plurality of structures having the predetermined height and spacing on the second surface of the layer of porous material; The method further comprising:

[0144] Embodiment 44 is a method described in any one of embodiments 43 and 45 to 46, wherein the first pattern and the second pattern have the same predetermined height and predetermined spacing.

[0145] Embodiment 45 is a method described in any one of embodiments 43 to 44 and 46, wherein the first pattern has at least one of a different predetermined height and a different predetermined spacing compared to the second pattern.

[0146] Embodiment 46 is a method described in any one of embodiments 43 to 45, wherein the step of providing a layer of porous material includes providing a roll of porous material and the stamp, and the second stamp is a circular stamp configured to form a pattern of the multiple structures in a roll-to-roll process or a roll-to-plate process.

[0147] Embodiment 47 is a filtration medium comprising a layer of porous material having a patterned outer surface including a plurality of raised structures, each of the plurality of raised structures having a height in the range of 1 μm to 40 μm, and a center-to-center spacing between paired plurality of raised structures in the range of 1 μm to 100 μm.

[0148] Embodiment 48 is a filtration medium described in embodiment 47, wherein the patterned outer surface exhibits a sliding angle of 35° or less, 30° or less, 25° or less, or 20° or less when exposed to a liquid having a surface tension of 20 mN / m or more and measured using a droplet size of 20 μm.

[0149] Embodiment 49 is a filtration medium described in embodiment 47 or 48, wherein the patterned surface in contact with a contaminant exhibits a contact angle that is at least 5° higher, at least 15° higher, at least 20° higher, or at least 25° higher than the porous material not having a patterned surface.

[0150] Embodiment 50 is a filtration medium described in any one of embodiments 47 to 49, wherein the patterned surface in contact with a contaminant exhibits a receding contact angle of 50° or more, 60° or more, 70° or more, 80° or more, or 90° or more.

[0151] Embodiment 51 is a filtration medium described in any one of embodiments 47 to 50, wherein the plurality of raised structures have a pattern substance fraction in the range of 0.1 to 0.8, 0.2 to 0.75, or 0.25 to 0.75.

[0152] Embodiment 52 is a filtration medium according to any one of embodiments 47 to 51, wherein the porous material is a membrane.

[0153] Embodiment 53 is a filtration medium described in embodiment 52, wherein the membrane comprises one of polypropylene, polyethylene, polyester, polyethersulfone, polysulfone, expanded polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyacrylonitrile, polycarbonate, and cellulose acetate.

[0154] Embodiment 54 is a filtration medium described in any one of embodiments 47 to 53, wherein the layer of porous material further comprises a coating that increases the oleophobicity of the layer.

[0155] Embodiment 55 is the filtration medium of embodiment 54, wherein the coating is a fluoropolymer, and optionally the coating comprises a perfluoropolyether (PFPE) bottle brush polymer.

[0156] Embodiment 56 is the filtration medium of any one of embodiments 47 to 55, wherein the porous material has a pore size of at least 0.05 μm and a pore size of at least 0.05 cfm / ft at 0.5 inches of water pressure differential prior to the porous material being patterned. 2 (0.025 cm at 125 Pa) 3 / s / cm 2 ) a filtration medium having a Frazier permeability of 100%.

[0157] Embodiment 57 is the filtration medium of any one of embodiments 47 to 56, wherein the patterned layer of porous material has a filtration rate of 0.1 cfm / ft at 0.5" water column differential pressure. 2 (0.051 cm at 125 Pa) 3 / s / cm 2 )~3cfm / ft at 0.5" water column 2 (1.52 cm at 125 Pa 3 / s / cm 2 ), 0.3cfm / ft at 0.5" water column 2 (0.15 cm at 125 Pa 3 / s / cm 2 )~3cfm / ft at 0.5" water column 2 (1.52 cm at 125 Pa 3 / s / cm 2 ), or 0.5 cfm / ft at 0.5" water column 2 (0.25 cm at 125 Pa 3 / s / cm 2 )~3cfm / ft at 0.5" water column 2 (1.52 cm at 125 Pa 3 / s / cm 2 ) a filtration medium having a Frazier permeability of 100%.

[0158] Embodiment 58 is a filtration medium described in any one of embodiments 47 to 57, wherein the layer of porous material comprises a hierarchical structure including at least micro-scale features and macro-scale features, and the macro-scale features are formed by pores of the porous material, or the plurality of raised structures, or both.

[0159] Embodiment 59 is the filtration medium of embodiment 58, wherein the porous material comprises a phase inversion material.

[0160] Embodiment 60 is the filtration medium of embodiment 58 or 59, wherein the porous material comprises polypropylene, polyethylene, polyester, polysulfone, polyethersulfone, polyvinylpyrrolidone, polyvinylidene fluoride, polyamide (nylon), polyacrylonitrile, polycarbonate, cellulose acetate, or a combination thereof, preferably the porous material comprises polyethersulfone, polysulfone, polyvinylidene fluoride, or cellulose acetate.

[0161] Embodiment 61 is a filtration medium described in any one of embodiments 47 to 60, wherein all of the pairs of raised structures have equal spacing.

[0162] Embodiment 62 is a filtration medium described in any one of embodiments 47 to 61, wherein the raised structures include pillars, ribs, or splines.

[0163] Embodiment 63 is a degassed battery pack comprising one or more batteries disposed inside an enclosed container and cooling oil at least partially surrounding the one or more batteries, the enclosed container comprising one or more venting ports and a degassing medium blocking the one or more venting ports, the degassing medium comprising a filtration medium described in any one of embodiments 1 to 62.

[0164] Embodiment 64 is a degassed battery pack as described in embodiment 63, wherein the one or more batteries are lithium ion batteries.

[0165] Embodiment 65 is a degassed battery pack as described in embodiment 63 or 64, wherein the degassing medium is a patterned cellulose acetate medium, and the degassing medium may be coated.

[0166] Embodiment 66 is a degassed package comprising one or more venting ports blocked by a degassing medium, the degassing medium comprising a filtration medium described in any one of embodiments 1 to 62.

[0167] Embodiment 67 is a vented package as described in embodiment 66, wherein the one or more vent ports are located on a cap or insert.

[0168] Embodiment 68 is a degassed package according to embodiment 66 or 67, wherein the degassing medium is a patterned cellulose acetate medium, and the degassing medium may be coated. EXAMPLES

[0169] The dimensions of the patterns were measured using a 3D Laser Scanning Confocal Microscope (VK-X, Keyence, Osaka, Japan). The dimensions can be recognized by taking and measuring line profiles from the 3D images. The height of the patterns can also be obtained by plotting a histogram of the height data over the entire 3D image.

[0170] The samples were imprinted using a Nanoimprint Lithography station (CNI v2.1, NIL Technology, Kongens Lyngby, Denmark). The imprint pressure ranged from 0.3 to 11 bar and the imprint temperature ranged from 0 °C to 200 °C.

[0171] The media used in the following examples (referred to as Media 1) had an average pore size of about 0.2 μm, a thickness of about 9 mils, and a median thickness of about 0.15 cfm / ft 2 (0.076 cm at 125 Pa) 3 / s / cm 2 ) is an expanded PTFE membrane having a Frazier air permeability of 1.0%.

[0172] Example 1 One side of "Medium 1" was patterned via nanoimprint lithography. The patterned stamp was used in an imprinting process to fabricate via photolithography using SU-8 photoresist (Kayaku advanced Materials, Massachusetts, USA) on a silicon wafer. The pattern imprinted on the ePTFE was an array of lines with s=10 μm, h=4.2 μm, φ=0.5. To measure the contact angle and sliding angle, a liquid drop (20 μL) was pipetted onto the patterned ePTFE surface.

[0173] The contact angle and sliding angle of the substrate were measured using a DropMaster DM-701 contact angle meter equipped with a tilting stage (Kyowa Interface Science Co., Ltd.; Niiza, Japan). Measurements were performed using a standard camera lens setting, calibrated with a 6 millimeter (mm) calibration standard, and using the FAMAS software package (Kyowa Interface Science Co., Ltd.; Niiza, Japan). Measurements were performed only after the droplet reached equilibrium on the surface (i.e., when the contact angle and exposed volume of the droplet were constant for 1 min). Measurements were performed on the droplet in contact with the substrate only (i.e., the droplet was not in contact with any surface supporting the substrate).

[0174] Contact angles with the first and second liquids were measured using a 20 μL drop of each liquid placed on the substrate sample. Contact angles were measured using a tangent fit and calculated from the average of three to five independent measurements taken on different areas of the substrate.

[0175] The sliding angles for the first and second liquids were measured using a 20 μL drop of each liquid placed on a substrate sample (in this case, a patterned or unpatterned film). The stage was set to rotate to 90° at a rotation speed of 2 degrees per second (° / sec). Rotation was stopped at the point where the drop rolled freely or the back contact line had moved at least 0.4 millimeters (mm) relative to the media surface. The angle at which the rotation was stopped was measured and this angle was defined as the sliding angle. If the drop did not roll off at 90°, the value was recorded as 90°. If the drop rolled off during the deposition process, the value was recorded as 1°. The reported value was calculated from the average of five independent measurements taken on different areas of the media. When data were measured for linear structures, they were measured parallel to the inclined plane.

[0176] Contact angles and sliding angles were also measured on an unpatterned but otherwise identical ePTFE surface. The first liquid, "Liquid 1," was water (72 mN / m), and the second liquid, "Liquid 2," was a homogeneous mixture of water:IPA (80:20) (33 mN / m).

[0177] Table 2 shows that the patterned film exhibits superhydrophobic performance (θ>150° and sliding angle<10°). In general, the patterned film exhibits a larger contact angle and a smaller sliding angle.

[0178] [Table 2]

[0179] Example 2 One side of "Medium 1" was patterned via nanoimprint lithography. The patterned stamp was used in an imprinting process to fabricate via photolithography using SU-8 on a silicon wafer. The pattern imprinted on the ePTFE was an array of lines with s=25 μm, h=10 μm, φ=0.5. The ePTFE membranes (patterned and non-patterned) were dip-coated in 3 (w / v)% fluoroacrylate polymer in Novec 7200 (3M, Saint Paul, MN, USA) to make it oleophobic. Contact angles and sliding angles were measured using 20 μL droplets as in Example 1. "Liquid 1" was water (72 mN / m) and "Liquid 2" was a homogeneous mixture of 80:20 water:IPA (33 mN / m).

[0180] Table 3 shows that for both liquids, patterning the film results in lower observed sliding angles and higher contact angles. Simply coating the film with an oleophobic coating does not improve liquid drainage, whereas in this case it is both coated and patterned.

[0181] [Table 3]

[0182] Example 3 One side of cellulose acetate (CA0459025, Sterlitech, Kent, WA, USA) was patterned via nanoimprint lithography (Figure 8C). The patterned stamp was used in an imprinting process to fabricate via photolithography using SU-8 on a silicon wafer. The pattern imprinted on the cellulose acetate was an array of lines with s = 10 μm, φ = 0.5. The height of the patterns was varied as seen in Table 4. The cellulose acetate films (patterned and non-patterned) were dip-coated in 3 (w / v)% fluoroacrylate polymer in Novec 7200 (3M, Saint Paul, MN, USA) to make them oleophobic.

[0183] The contact angle and sliding angle were measured using a 20 μL droplet in the same manner as in Example 1. The liquid tested was gear oil (Hypoid Gear Oil HGO-1 GL-5 75W-85, Honda, Minato-ku, Tokyo, Japan).

[0184] The Frazier permeability of each sample was measured before and after contamination with gear oil. To contaminate, gear oil was pipetted onto each sample, the sample was held vertically for 30 minutes, and the permeability was measured after allowing the oil to drain.

[0185] Table 4 shows that patterning cellulose acetate reduces the sliding angle and preserves the transparency, however, if the height is too low, the pattern is lost. Patterns with a height of only 2.6 μm do not perform significantly better than unpatterned cellulose acetate. Only the pattern with a height of 4.0 μm retains significantly more transparency than the unpatterned film. Furthermore, the image in FIG. 8C supports that the gear oil is in a Cassian state on the patterned cellulose acetate, since liquid is only present on top of the pattern and no liquid is found at the bottom of the pattern.

[0186] [Table 4]

[0187] Example 4 One side of "Medium 1" was patterned via nanoimprint lithography. The patterned stamp was used in an imprinting process to create a pattern via photolithography using SU-8 on a silicon wafer. The imprinted pattern on the ePTFE was an array of lines with s=10 μm, h=3.6 μm, φ=0.5. The ePTFE membrane (patterned and non-patterned) was dip-coated in 3 (w / v)% fluoroacrylate polymer in Novec 7200 (3M, Saint Paul, MN, USA) to make it oleophobic. The contact angle and sliding angle were measured using a 20 μL drop as in Example 1. Diesel exhaust fluid (DEF, blueDEF, Old World Industries, Northbrook, IL, USA) and engine oil (Mobil 1 Advanced Fuel Economy 0W-20, Mobil 1, Irving, TX, USA) were used. DEF has a surface tension of 73 mN / m and engine oil has a surface tension of 29 mN / m.

[0188] Table 5 shows the permeability before and after contamination with each fluid. After contamination with DEF, the permeability is not affected because ePTFE easily repels water-based contaminants. However, after contamination with engine oil on the unpatterned ePTFE membrane, the permeability does not recover. After contamination with engine oil, the patterned ePTFE has a higher permeability recovery than the unpatterned ePTFE. This is because the patterned ePTFE membrane has a higher ability to wick away liquids. For liquids with a surface tension lower than 29 mN / m, P is calculated as in Equation 3. wet For example, a surface tension of 24 mN / m would require a maximum spacing between features of 1 μm.

[0189] [Table 5]

[0190] Example 5 Polyethersulfone (PES:M w 72,000, dispersion index: 3.4), polyvinylpyrrolidone (PVP:M w Dope solutions of the polymers were prepared using PES (360,000; Sigma Aldrich) and N-methyl-2-pyrrolidinone (NMP; Sigma Aldrich). The composition for all dope solutions used in Examples 5-7 was 20 wt% PES, 10 wt% PVP, and 70 wt% NMP. The dope solutions were cast onto silicon wafers that had been patterned via photolithography using SU-8 photoresist.

[0191] The patterned silicon wafer used in this example contained an array of squares with s=100 μm and a pattern substance fraction (φ) of 0.25. The dope solution was cast onto the patterned silicon wafer using a casting knife to a casting thickness of 100 μm. The cast polymer film was first subjected to vapor-induced phase separation (VIPS) using fan-circulated humid air (RH; 99%) for 30 seconds, and then non-solvent-induced phase separation (NIPS) by immersing the film cast onto the wafer in water heated to 60° C. for 1 minute. The film was then rinsed in a bath of deionized water at room temperature for at least 5 minutes. Figure 22A shows a film cast using this process. Air bubbles are clearly visible adjacent to each structure.

[0192] Another film was cast and then placed in a vacuum chamber before undergoing the VIPS process, which eliminated the air bubble defects, as seen in Figure 22B.

[0193] Example 6 In Example 6, the same dope solution as that used in Example 5 was used. The dope solution was cast onto a patterned silicon wafer containing 10 μm lines and having a pattern substance fraction (φ) of 0.75. The cast film was placed in a vacuum chamber to eliminate air bubble defects. The film was then subjected to VIPS for 45 seconds at 99% RH with fan circulating moist air. The film was then immersed in a 60° C. water bath for 1 minute (NIPS). The film was then rinsed in a deionized water bath before being peeled off from the silicon wafer.

[0194] Figure 23A shows a laser confocal image of the PES membrane so obtained. Schematic diagrams of the membrane are shown in Figures 23B and 23C. The horizontal stripes T, which represent smaller pores, are at the top of the pattern. The alternative stripes B, which represent larger pores, are at the bottom of the pattern. It is clear that there is a difference in pore size between the top and bottom of the pattern, which is due to the shrinkage of the membrane during the casting process.

[0195] The following hypothesis is made: the Cassie liquid in this pattern is in contact only with the top of the pattern, leaving the bottom of the pattern open to air flow.

[0196] Example 7 In Example 7, the same dope solution was used as in Example 5. The dope solution was cast onto a patterned silicon wafer consisting of 50 μm lines with a pattern substance fraction (φ) of 0.5. The cast film was placed in a vacuum chamber to eliminate air bubble defects. The film was then subjected to VIPS for 5 minutes at 99% RH with fan circulating moist air. The film was then immersed in a water bath at 55° C. for 1 minute (NIPS). The film was then rinsed in a deionized water bath before being peeled off from the silicon wafer.

[0197] FIG. 24 shows an SEM image of the resulting PES membrane. The square cross-section of the pattern is evident, with sharp corners at the top of the pattern. It was observed that phase inversion micromolding, compared to other methods (e.g., imprinting), results in more defined features, as seen in FIG. 24. It is hypothesized that this is because phase inversion micromolding relies on the penetration of a liquid polymer solution into a patterned substrate. For example, imprinting relies on a solid polymer softening and deforming at high temperatures, which typically results in less defined features (especially if transparency is to be maintained). For comparison, an image of the imprinted structure is shown in FIG. 25.

[0198] Example 8 Cellulose acetate (CA:M n A polymer dope solution was prepared using CA (CA; 30,000, Sigma Aldrich) and N-methyl-2-pyrrolidinone (NMP; Sigma Aldrich). The composition of the dope solution was 8 wt% CA, 19 wt% DI(H2O), and 73 wt% NMP. The dope solution was cast onto "Medium 1" with a casting knife at a thickness of 100 μm. The cast membrane was subjected to VIPS for 4 minutes at 99% RH with fan-circulated moist air. The membrane was then immersed in a 53°C water bath for 1 minute (NIPS) and then rinsed in a bath of deionized water for at least 5 minutes.

[0199] Figure 26 shows a cross section of the composite membrane formed. The cellulose acetate (CA) forms a brittle membrane that can be supported by a support structure. The ePTFE membrane provides this function and also acts as an efficiency layer. For example, an ePTFE membrane with high water inlet pressure can be used. The composite membrane has a dual function with an efficient ePTFE layer and a repellent cellulose acetate layer. The cellulose acetate layer is hierarchical and, if patterned, will provide the benefits of liquid contaminant rejection and permeability recovery as previously described.

[0200] Example 9 Patterned and non-patterned cellulose acetate ("CA") membranes were exposed to E-Fluids oil (manufactured by Shell) (SL2808 Shell E-Fluids E6 iX, Shell, Beijing, China), used in electric vehicles. The permeability of the membranes was measured before and after exposure to the oil using the same test method described in Example 3. The membranes were compared to a commercially available ePTFE membrane [thickness; approximately 1.9 mil, Frazier permeability; approximately 0.23 cfm / ft at 0.5" water column]. 2 (0.12 cm at 125 Pa 3 / s / cm 2 )]. The results are shown in Figure 27. Enhanced permeability recovery was observed for the patterned cellulose acetate membrane.

[0201] Unless otherwise indicated, all numbers expressing sizes, amounts, and physical properties of shapes used in the specification and claims are to be understood in all instances as being modified by the term "about". Thus, unless otherwise indicated, the parameters recited in the foregoing specification and appended claims are approximations and may be varied depending on the desired properties desired to be obtained by one of ordinary skill in the art using the teachings disclosed herein. When numerical ranges are used by indicating endpoints, they include all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and all ranges within that range.

[0202] The above description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Furthermore, it is not intended to limit the embodiments to water-based inks or inks containing water. Many modifications and variations are possible in light of the above teachings. Any or all of the disclosed embodiments may be applied alone or in various combinations, but are not meant to be limiting, but are purely illustrative. It is intended that the scope of the invention not be limited to this detailed description, but rather be determined by the appended claims.

Claims

1. A filtration medium comprising a layer of porous material having a patterned outer surface including a plurality of raised structures, each raised structure in the plurality of configurations having a height in the range of 1 μm to 40 μm, and a center-to-center spacing between the raised structures in pairs in the plurality of configurations in the range of 1 μm to 100 μm. filtration media.

2. the plurality of raised structures having a pattern entity fraction ranging from 0.1 to 0.8, 0.2 to 0.75, or 0.25 to 0.75; 2. The filtration medium of claim 1.

3. the porous material is a membrane, the membrane comprising one of polypropylene, polyethylene, polyester, polyethersulfone, polysulfone, expanded polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyacrylonitrile, polycarbonate, and cellulose acetate; 2. The filtration medium of claim 1.

4. the layer of porous material further comprises a coating that increases the oleophobicity of the layer, optionally the coating is a fluoropolymer, optionally the coating comprises a perfluoropolyether (PFPE) bottle brush polymer; 2. The filtration medium of claim 1.

5. The porous material has a pore size of at least 0.05 μm and a pore size of at least 0.025 cm at 125 Pa, measured according to ASTM D737-18, prior to the porous material being patterned. ３ / s / cm ２ having a Frazier permeability of 2. The filtration medium of claim 1.

6. The patterned layer of porous material has a microporous surface area of ​​0.051 cm at 125 Pa, measured according to ASTM D737-18. ３ / s / cm ２ ~1.52 cm at 125 Pa ３ / s / cm ２ , 0.15 cm at 125 Pa ３ / s / cm2 ~ 1.52 cm at 125 Pa ３ / s / cm2, or 0.25 cm at 125 Pa ３ / s / cm ２ ~1.52 cm at 125 Pa ３ / s / cm2 Frazier permeability, 2. The filtration medium of claim 1.

7. the layer of porous material comprises a hierarchical structure comprising at least micro-scale features and macro-scale features, the macro-scale features being formed by pores of the porous material, or the plurality of raised structures, or both, and optionally the porous material comprises a phase inversion material; 2. The filtration medium of claim 1.

8. 1. A degassing device comprising: an opening configured to vent gas from the enclosure; and a venting element secured within said venting apparatus and forming a liquid-tight, gas-permeable seal of said opening; and the venting element comprises the porous material of claim 1. Gas venting device.

9. A method for producing a layer having a patterned surface, comprising the steps of: applying a stamp to a first side of a layer of porous material at a predetermined temperature and pressure to form a pattern of raised structures on a surface of the layer, the stamp including a patterned surface corresponding to a negative of the pattern of raised structures, each raised structure having a height in the range of 1 μm to 40 μm, and a center-to-center spacing between the raised structures in a plurality of paired configurations in the range of 1 μm to 100 μm; method.

10. the stamp comprises a roll or a plate, and applying the stamp to the layer of porous material comprises a roll-to-roll process or a roll-to-plate process; 10. The method of claim 9.

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