Selective densification of drawn polyethylene.

Abstract

To provide a material that can reliably provide highly accurate and precise features on a microscopic scale. [Solution] A method for densifying an expanded polyethylene (ePE) substrate, the method comprising the steps of: providing an ePE substrate having a first density and a first size; selectively densifying a portion of the ePE substrate to form a densified portion of the ePE substrate, wherein the densified portion of the ePE substrate has a second density greater than the first density, and the densified portion of the ePE is a densified pattern; and shrinking the ePE substrate to a second size, thereby reducing the densified pattern to a fine densified pattern, wherein the second size is smaller than the first size, and the fine densified pattern is smaller than the densified pattern.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Provisional Application No. 63 / 433,123, filed December 16, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to apparatus, systems, and methods for densifying expanded polyethylene (ePE), and more particularly, to apparatus, systems, and methods for densifying expanded polyethylene (ePE) that can be used in medical devices. [Background technology]

[0003] The method used to process a material can impart certain qualities to the processed material. These certain qualities may be necessary for the processed material to function toward its intended purpose, or may enable the processed material to be used in new ways. The choice of processing method is important in various industries, including but not limited to the medical device industry, and more specifically for implantable medical devices. However, processed materials may be used in a variety of industries, and properties desired in one industry may be important in others as well. Summary of the Invention [Problem to be solved by the invention]

[0004] Medical devices often require small features to aid in treatment or to interact with small molecules in the body. For example, a medical treatment may require the medical device to interact with cells to make the treatment effective. In some instances, the small features may be required to be located within the lumen of the medical device. However, providing small-scale features with high precision and accuracy is difficult. There is a need for materials that can reliably provide small-scale features with high precision and accuracy. [Means for solving the problem]

[0005] The present disclosure relates to methods for densifying ePE substrates, and articles and devices produced thereby, where densification can include fine or micro-scale embossing. For example, articles and devices produced thereby can include densifying selective portions of an ePE substrate to generate a densified pattern, and then reducing the size of the ePE substrate to form a micropattern that can exhibit a desired set of features. Such desirable features of the micropattern can include promoting tissue penetration, antithrombogenicity, migration resistance, and controlling laminar flow direction.

[0006] According to one example ("Example 1"), a method for densifying an expanded polyethylene (ePE) substrate optionally includes the steps of providing an ePE substrate having a first density and a first size; selectively densifying a portion of the ePE substrate to form a densified portion of the ePE substrate, wherein the ePE substrate has the first density and the first size, and the densified portion of the ePE substrate has a second density greater than the first density, the densified portion of the ePE being a densified pattern; and shrinking the ePE substrate to a second size, thereby reducing the densified pattern to a fine densified pattern, wherein the second size is smaller than the first size and the fine densified pattern is smaller than the densified pattern.

[0007] According to yet another example ("Example 2") to Example 1, selective densification of portions of the ePE substrate is accomplished by embossing.

[0008] According to yet another example ("Example 3") of Example 1, selectively densifying portions of the ePE substrate further includes applying heat and pressure to the ePE substrate.

[0009] According to yet another example ("Example 4") of Example 3, applying heat and pressure to the ePE substrate includes contacting the ePE substrate with a member at about 110°C to about 180°C.

[0010] According to yet another example ("Example 5") to Example 1, the method further includes forming the ePE substrate into an ePE article.

[0011] According to yet another example ("Example 6") to Example 5, an ePE substrate is formed into a medical device.

[0012] According to yet another example ("Example 7") to Example 6, the medical device includes an implantable medical device.

[0013] According to yet another example ("Example 8") of Example 1, shrinking the ePE substrate to a second size further comprises applying heat to the ePE substrate.

[0014] According to yet another example ("Example 9") in contrast to Example 1, the shape of the fine densification pattern is the same as the shape of the densification pattern.

[0015] According to yet another example ("Example 10") to Example 1, the micro-densification pattern is configured to promote tissue infiltration.

[0016] In yet another example ("Example 11") in contrast to Example 1, the fine densified pattern is configured for anti-thrombogenicity.

[0017] According to yet another example ("Example 12") to Example 1, the fine densification pattern is configured to direct laminar flow across the surface of the fine densification pattern.

[0018] According to one example ("Example 13"), a method for generating a pattern on an expanded polyethylene (ePE) substrate optionally includes the steps of providing an ePE substrate having a first density and a first size; applying heat and pressure to the ePE substrate using a patterned member, wherein the ePE substrate has the first density and the first size, and selectively densifying a first portion of the ePE substrate to a second density with the patterned member, such that the ePE substrate has a first densification pattern in the first portion of the ePE substrate; and shrinking the ePE substrate to a second size, such that the first densification pattern is reduced to a second densification pattern having a series of features, wherein the second densification pattern is smaller than the first densification pattern.

[0019] According to yet another example ("Example 14") to Example 13, the patterned member used to apply heat and pressure is a mandrel.

[0020] According to yet another example ("Example 15") to Example 14, the mandrel has a textured pattern and the first densification pattern is a corresponding textured pattern.

[0021] According to yet another example ("Example 16") of Example 13, applying heat and pressure to the ePE substrate includes contacting the ePE substrate with a patterned feature at about 110°C to about 180°C.

[0022] According to yet another example ("Example 17") relative to Example 13, the first densification pattern includes a first depth ratio and the second densification pattern includes a second depth ratio, and the first depth ratio and the second depth ratio are substantially the same.

[0023] According to one example ("Example 18"), an expanded polyethylene (ePE) article comprises an ePE substrate molded into an ePE article, the ePE article comprising a micropattern, the micropattern being formed by a selective densification patterning and shrinkage process.

[0024] In yet another example ("Example 19") to Example 18, the micropattern is textured for antithrombogenic purposes.

[0025] According to yet another example ("Example 20") to Example 18, the micropattern is configured to promote tissue infiltration.

[0026] According to yet another example ("Example 21") to Example 18, the micropattern is configured to direct laminar flow across the surface of the ePE article.

[0027] According to yet another example ("Example 22") to Example 18, the micropattern is configured to promote tearing of the ePE article along the propagation path.

[0028] According to yet another example ("Example 23") in contrast to Example 18, the micropattern is configured to promote migration resistance.

[0029] According to yet another example ("Example 24") in contrast to Example 18, the micropattern includes one repeating shape.

[0030] In yet another example ("Example 25") in contrast to Example 18, the fine pattern is a random pattern.

[0031] The foregoing examples are merely examples and should not be construed as limiting or otherwise narrowing the scope of any of the inventive concepts provided by the present disclosure. While multiple examples are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. [Brief explanation of the drawings]

[0032] The accompanying drawings are included to provide a further understanding of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description serve to explain the principles of the present disclosure.

[0033] [Figure 1] FIG. 1 is a block diagram of a method 100 for densifying an expanded polyethylene (ePE) substrate, the method including providing, selectively densifying, and shrinking steps, according to some embodiments.

[0034] [Figure 2A] FIG. 1 is a front view of one embodiment in which an ePE substrate is provided in a first size, selectively densified, and shrunk to a second size according to some embodiments.

[0035] [Figure 2B] FIG. 2B is an illustrative bottom view of FIG. 2A, according to some embodiments.

[0036] [Figure 3] FIG. 2 is a block diagram of a method for densifying the expanded polyethylene (ePE) substrate of FIG. 1, the method further comprising a molding step, according to some embodiments.

[0037] [Figure 4] 1 is a diagrammatic representation of one embodiment of forming an ePE substrate into a tubular ePE article, according to some embodiments.

[0038] [Figure 5] FIG. 1 is a block diagram of a method for producing a pattern on an expanded polyethylene (ePE) substrate, the method including providing, applying heat and pressure, and shrinking, according to some embodiments.

[0039] [Figure 6]FIG. 6 is a side view of producing a pattern on an expanded polyethylene (ePE) substrate according to the method of FIG. 5, according to some embodiments.

[0040] [Figure 7] FIG. 6 is a block diagram of a method for producing a pattern on the ePE substrate of FIG. 5, the method further comprising a molding step, according to some embodiments.

[0041] [Figure 8A] 1 is a diagrammatic representation of an ePE substrate having a densified pattern, according to some embodiments. [Figure 8B] 1 is a diagrammatic representation of an ePE substrate having a densified pattern, according to some embodiments.

[0042] Detailed Description Definitions and Terminology The present disclosure is not intended to be construed in a limiting sense, for example, the terms used in this application should be interpreted broadly in the context of the meaning that one skilled in the art would give to those terms.

[0043] With respect to terms involving imprecision, the terms "about" and "approximately" may be used interchangeably to refer to measurements that include the stated measurement as well as measurements that are reasonably close to the stated measurement. A measurement that is reasonably close to the stated measurement deviates reasonably slightly from the stated measurement to an extent that is understood and easily identified by one of ordinary skill in the art. Such deviations may result from, for example, measurement error, differences in calibration of measuring and / or manufacturing equipment, human error in reading and / or setting measurements, minor adjustments made to optimize performance and / or structural parameters to account for differences in measurements associated with other components, specific implementation scenarios, imprecise adjustment and / or manipulation of objects by humans or machines, etc. If it is determined that a person of ordinary skill in the art would not be able to easily identify such a reasonably small difference, the terms "about" and "approximately" may be understood to mean ±10% of the stated value.

[0044] As used herein, the term "laminate" refers to multiple layers of films, composites, or other materials, such as, but not limited to, polymers, such as, but not limited to, elastomers, elastomeric or non-elastomeric materials, and combinations thereof.

[0045] As used herein, the term "film" generally refers to one or more of a membrane, a composite, or a laminate.

[0046] As used herein, the term "biocompatible material" generally refers to any material that has biocompatible properties, including synthetic materials, such as, but not limited to, biocompatible polymers, or biological materials, such as, but not limited to, bovine pericardium. The biocompatible material can include a first film and a second film, as described herein for various embodiments.

[0047] As used herein, the term "polyethylene" (PE) includes all types of polyethylene, including but not limited to oriented polyethylene (ePE).

[0048] As used herein, the term "selective densification" generally refers to densification at predetermined locations on a substrate and includes various degrees of densification, including partial densification, where the substrate maintains a porous and open microstructure after densification, and full densification, where the substrate has a closed microstructure. Selective densification can include, but is not limited to, densification along the thickness of the substrate or the length of the substrate.

[0049] As used herein, the term "shrink" generally refers to a reduction in size such that the substrate or pattern is smaller in size than it was before shrinking.

[0050] As used herein, the term "shrink" generally refers to reducing the size of a substrate or pattern such that the substrate or pattern is smaller in size than it was before shrinking. Description of Various Embodiments

[0051] Those skilled in the art will readily appreciate that the various aspects of the present disclosure may be implemented by any number of methods and apparatus configured to perform the intended functions. It should also be noted that the accompanying drawings referred to herein are not necessarily drawn to scale and may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawings should not be construed as limiting.

[0052] The present disclosure relates to methods for densifying ePE substrates, and articles and devices produced thereby, where densification of the ePE substrate can include fine or micro-scale embossing. For example, articles and devices produced by the methods can include densifying selective portions of the ePE substrate to generate a densified pattern on the ePE substrate, and then reducing the size of the ePE substrate to form a micropattern that can exhibit a desired set of features. Such desirable features of the micropattern can include promoting tissue penetration, antithrombogenicity, and controlling laminar flow direction.

[0053] The method illustrated in FIG. 1 is provided as an example of various features of the present invention, and although combinations of the illustrated features are clearly within the scope of the present invention, the example and its illustration do not imply that the inventive concepts provided herein are limited to one or more features illustrated in FIG. 1 and do not include fewer, additional, or alternative features.

[0054] FIG. 1 is a block diagram of a method 100 for densifying an expanded polyethylene (ePE) substrate, the method including providing, selectively densifying, and shrinking steps according to some embodiments. Method 100 can be implemented in a variety of contexts, including, but not limited to, medical devices, which may include implantable medical devices. Various forms of ePE can be implemented in the method, including, but not limited to, membranes, films, tapes, tubes, and the like. It is further understood that ePE can have a variety of properties, including thickness, fibril and node structure, porosity, density, and the like. Accordingly, the embodiments discussed herein are not limited to any particular initial condition or morphology, but are understood to broadly encompass any ePE starting material suitable for the described method.

[0055] In some embodiments, as shown in FIG. 1, a method 100 for densifying an ePE substrate optionally includes step 110 of providing the ePE substrate in a first size, step 120 of selectively densifying a portion of the ePE substrate, and step 130 of shrinking the ePE substrate to a second size.

[0056] Further to Figure 1, the ePE substrate also has a first density. The ePE substrate also has a first porosity. The first size can be defined by one or both of a longitudinal dimension or a lateral dimension. The ePE substrate can be provided as a square, rectangular, or other shape and, therefore, can include various other dimensions for determining the size of the substrate (e.g., radius, length, width, etc.).

[0057] With further reference to FIG. 1 , a densified portion of the ePE substrate can be formed by selectively densifying a portion of the ePE substrate (step 120). Selective densification refers to increasing the density of the selectively densified substrate by densifying a portion of the ePE substrate. In some embodiments, selective densification involves increasing the density of the selectively densified portion of the substrate while maintaining the porosity of the substrate (e.g., not fully densifying so that an open microstructure is maintained). In some embodiments, selective densification involves increasing the density without preserving porosity (e.g., fully densifying so that an open microstructure is absent). The portion of the substrate that is not selectively densified is a porous portion, which defines a non-densified portion. Selective densification can be performed throughout the entire thickness of the ePE substrate or along the length of the ePE substrate. The densified portion of the ePE is not necessarily densified throughout the entire thickness of the ePE substrate, in which case at least some porosity will be maintained within the thickness of the ePE substrate. In some embodiments, non-densified portions of the ePE substrate can be selectively masked, leaving the non-densified portions undensified and porous.

[0058] The densified portion of the ePE substrate can have a second density greater than the first density. In some embodiments, the densified portion of the ePE substrate can have a second porosity less than the first porosity. The second porosity can retain porosity but reduce pore size due to shrinkage. The locations of shrinkage and porosity can be controlled to specific locations or portions of the ePE substrate. The densified portion of the ePE substrate can be provided in a densification pattern. Step 120 of selectively densifying a portion of the ePE substrate can be performed on a single portion of the ePE substrate or on two or more portions of the ePE substrate. The densified portion can be generated on the ePE substrate at any location on the ePE substrate, including, but not limited to, the center, left, or right portions of the ePE substrate. In other embodiments, step 120 of selectively densifying a portion of the ePE substrate can be performed on multiple portions of the ePE substrate. In some embodiments, the densified portion covers substantially all of the surface of the ePE substrate. In other embodiments, step 120 of selectively densifying portions of the ePE substrate is performed in one or more of a longitudinal direction, a transverse direction, or a diagonal direction relative to the axis of the ePE substrate. In some examples, the densified portions are produced in a shape and depth such that the densification pattern has a certain shape and depth. It is understood that any shape or pattern of densification is contemplated herein and is not limited to those provided herein, which are provided as some examples of possible shapes and patterns.

[0059] In some embodiments, step 120 of selectively densifying a portion of the ePE substrate can be performed by embossing. Embossing a portion of the ePE substrate can produce a densification pattern having portions of raised features and portions of recessed features. In other embodiments, step 120 of selectively densifying a portion of the ePE substrate includes applying heat and / or pressure to the ePE substrate. Applying heat and / or pressure to the ePE substrate can include contacting the ePE substrate with a member. The member can be heated to a temperature near the glass transition temperature or melting temperature of the ePE substrate, which can be from about 110°C to about 180°C. For example, the member can be heated to a temperature of from about 110°C to about 120°C, from about 120°C to about 130°C, from about 130°C to about 140°C, from about 140°C to about 150°C, from about 150°C to about 160°C, from about 160°C to about 170°C, or from about 170°C to about 180°C. The member can be provided at any temperature suitable for producing a densified pattern. The member can be applied at a pressure greater than about 2 PSI. The applied pressure should be sufficient to avoid spreading or breaking the ePE substrate. The member can be contacted with the ePE substrate at any pressure suitable for producing a densified pattern. In some embodiments, heat and / or pressure can be applied to the ePE substrate at a constant value. In other embodiments, heat and / or pressure can be applied to the ePE substrate at a variable value. The selected temperature and / or pressure can affect the shape and depth of the densified pattern.

[0060] In some embodiments, embossing can be performed by manual embossing or automated embossing. Embossing can be performed by an external device (e.g., a soldering iron, a heated stamp, etc., not shown). Embossing can be performed by an internal device (e.g., a heated mandrel, etc., not shown). Embossing by an external device can selectively densify an outer surface portion of the ePE substrate. Embossing by an internal device can selectively densify an inner surface portion of the ePE substrate (e.g., the inner lumen of the tubular structure ePE article 430 in FIG. 4).

[0061] Still referring to FIG. 1 , in some embodiments, step 120 of selectively densifying a portion of the ePE substrate, such as central portion 227 of the ePE substrate (see FIG. 2A ), is followed by step 130 of shrinking the ePE substrate from a first size to a second size, where the second size is smaller than the first size. In some embodiments, step 130 of shrinking the ePE substrate to a second size is performed to reduce or shrink the size of the densification pattern to form a fine densification pattern. The fine densification pattern can be smaller in size than the initial densification pattern. In some embodiments, the ability to retain porosity in the ePE substrate after selective densification facilitates shrinkage of the ePE substrate, including the densified and non-densified portions of the ePE substrate. In these embodiments, the densified and non-densified portions of the ePE substrate shrink at different rates. For example, the non-densified portions can shrink proportionally more than the selectively densified portions. For example, proportional shrinkage can occur by providing an ePE substrate with fibrils oriented in a certain direction (e.g., substantially aligned in a particular direction), such that the ePE substrate tends to shrink proportionally more in a direction perpendicular to the fibrils. In some embodiments, selectively densifying portions of the ePE substrate can cause the ePE substrate to selectively shrink in non-densified portions. Shrinkage can occur in non-densified portions of the ePE substrate, where porosity is retained after selective densification. Shrinkage can also occur throughout the thickness of the densified portion of the ePE substrate, such that porosity is retained across a portion of the thickness. In some embodiments, the ePE substrate is fully densified upon shrinkage. In other embodiments, the ePE substrate can retain porosity upon shrinkage.

[0062] In some embodiments, the fine densification pattern has the same or substantially similar shape as the densification pattern. For example, if the shape of the densification pattern is a vertically elongated rectangle, the fine densification pattern retains its shape as a vertically elongated rectangle (see, e.g., Figures 2A-2B). In this regard, the fine densification pattern can retain its dimensional accuracy of shape upon size reduction. In other embodiments, the fine densification pattern has a different shape than the densification pattern. In still other embodiments, the first fine densification pattern can have a shape that is deformed from the shape of the densification pattern. In some embodiments, the fine densification pattern includes a depth. In some embodiments, the depth of the fine densification pattern can be the same as the depth of the densification pattern. In other embodiments, the ratio of the depth of the densification pattern to the longitudinal axis of the ePE substrate is the same as the ratio of the depth of the fine densification pattern to the longitudinal axis of the smaller densified ePE substrate. In this regard, the fine densification pattern can also retain its dimensional accuracy of depth upon size reduction. In yet other embodiments, the relative surface area coverage of the densified pattern on the densified ePE substrate can be the same as the relative surface area coverage of the fine densified pattern on the smaller densified ePE substrate. In some embodiments, the densified pattern is shrunk into the fine densified pattern upon shrinkage of the ePE substrate, such that the densified pattern shrinks proportionally with the ePE substrate.

[0063] In some embodiments, the micro-densification pattern imparts a series of features onto the ePE substrate. In some embodiments, the micro-densification pattern is configured to promote tissue penetration. In some embodiments, the micro-densification pattern is configured for anti-thrombogenicity. In some embodiments, the micro-densification pattern is configured to direct laminar flow across the surface of the micro-densification pattern. Further examples of series of features are shown in Figures 8A-8B.

[0064] In some embodiments, step 130 of shrinking the densified ePE substrate to a second size further includes applying heat to the densified ePE substrate. The densified ePE substrate can be heated to a temperature near the glass transition temperature or melting temperature of the densified ePE substrate, which may be about 110°C to about 180°C. For example, the densified ePE substrate can be heated to a temperature of about 110°C to about 120°C, about 120°C to about 130°C, about 130°C to about 140°C, about 140°C to about 150°C, about 150°C to about 160°C, about 160°C to about 170°C, or about 170°C to about 180°C. In some embodiments, the ePE substrate has heat applied via a heated environment (e.g., an oven). In some embodiments, applying heat to the ePE substrate selectively densifies the ePE substrate. In some embodiments, applying heat can cause the ePE substrate to naturally shrink or contract. The degree of contraction or retraction can correspond to the degree of stretching of the ePE substrate. In some embodiments, step 130 of shrinking the densified ePE substrate to a second size is performed when the densified ePE substrate is unconstrained. In other embodiments, step 130 of shrinking the densified ePE substrate to a second size can be performed when the densified ePE substrate is constrained in at least one dimension (e.g., longitudinally, laterally, etc.). For example, the ePE substrate can be constrained in the z-direction (e.g., thickness direction) to allow the ePE substrate to flow longitudinally and laterally when heat is applied. Constraining in the z-direction can include placing the ePE substrate between two plates (e.g., weighted plates) while placing a shim of the same thickness as the ePE substrate between the two plates to constrain the ePE substrate in the z-direction.

[0065] In some embodiments, the densified ePE substrate is cooled after being exposed to heat. The densified ePE substrate can be cooled at room temperature, placed in an environment that is colder than room temperature (e.g., a freezer), or slowly cooled in an environment that is warmer than room temperature. In some embodiments, the environment in which the densified ePE substrate is cooled can be a stable temperature or a variable temperature. In some embodiments, the variable temperature of the environment allows the densified ePE substrate to cool at a controlled rate. The cooling rate of the densified ePE substrate can be constant or variable.

[0066] 2A is a front view of one embodiment in which, according to some embodiments, an ePE substrate 210 is provided in a first size L1, selectively densified, and then shrunk to a second size L2. In some embodiments, the example in FIG. 2A follows the method 100 of FIG. 1 described above.

[0067] In Figure 2A, ePE substrate 210 has a first size L1. In some embodiments, this can follow method step 110 of providing an ePE substrate in a first size in Figure 1. In this embodiment, first size L1 is defined horizontally (e.g., width), but the first size can also be defined longitudinally (e.g., height), thicknesswise (e.g., thickness), or any combination of the lateral, longitudinal, and thicknesswise directions. In this embodiment, ePE substrate 210 is shown as a square, but other shapes of ePE substrate 210 are contemplated.

[0068] Further to FIG. 2A , portions of ePE substrate 210 can be selectively densified to form ePE substrate 220 having densified portions. In some embodiments, forming ePE substrate 220 having densified portions can be substantially similar to method step 120 for selectively densifying portions of an ePE substrate described in FIG. 1 . ePE substrate 220 having densified portions includes densification pattern 225, which has a shape. In this embodiment, densification pattern 225 has a vertically elongated rectangular shape. Other shapes for densification pattern 225 include, but are not limited to, rounded shapes, squares, or triangles. The shape can also extend laterally, diagonally, or in any other direction. In this embodiment, densification pattern 225 is defined by a central portion 227 of ePE substrate 220 having densified portions. In other embodiments, the densification pattern 225 can be formed on the left portion 221 of the densified ePE substrate 220, on the right portion 223 of the densified ePE substrate 220, or anywhere between the left portion 221 and the right portion 223. While one portion of the densified ePE substrate 220 has one densification pattern 225 in this embodiment, in other embodiments, multiple densification patterns can be created within the surface of the densified ePE substrate 220. In this embodiment, the densified ePE substrate 220 can be shrunk to an intermediate size LI. The intermediate size LI can be smaller than the first size L1. This size change can occur due to a local change in the depth of the densified ePE substrate 220 from the creation of the densification pattern 225, as shown in FIG. 2B . In other embodiments, the intermediate size LI can be the same as the first size L1.

[0069] Further to FIG. 2A , ePE substrate 220 having densified portions can be reduced to a retracted ePE substrate 230. Retracted ePE substrate 230 has a second size L2. In some embodiments, this can follow method step 130 of shrinking an ePE substrate to a second size in FIG. 1 . In this embodiment, second size L2 is smaller than first size L1. In this embodiment, second size L2 is also smaller than intermediate size L1. Retracted ePE substrate 230 includes a fine densification pattern 235. In some embodiments, fine densification pattern 235 is reduced in size from densification pattern 225. In this embodiment, densification pattern 235 is generated from densification pattern 225, and fine densification pattern 235 results from the step of shrinking ePE substrate 220 having densified portions. In this embodiment, fine densification pattern 235 retains the shape of densification pattern 225. In this embodiment, the fine densification pattern 235 also retains the same relative surface area coverage as the densification pattern 225 relative to the non-densified regions of the ePE substrate 220. In other embodiments, it is contemplated that the fine densification pattern 225 has a slightly different shape or slightly different surface area coverage than the densification pattern 225. In some embodiments, it is contemplated that the fine densification pattern 235 is modified from the densification pattern 225. For example, the densification pattern 225 can be substantially square in shape, and the fine densification pattern 235 can be substantially rectangular in shape. Other shapes, such as a substantially circular densification pattern 225 to a substantially oval densification pattern 235, are also contemplated. The change in shape can occur by implementing a restrained shrinkage in a certain direction, but can also occur by providing an ePE substrate with directionally oriented fibrils (e.g., substantially aligned in a particular direction), such that the ePE substrate tends to shrink proportionally more in a direction perpendicular to the fibrils.

[0070] FIG. 2B is an illustrative bottom view of FIG. 2A , according to some embodiments. ePE substrate 210 is shown with a first thickness T1. Densified ePE substrate 220 is shown with an intermediate thickness T1 and densified pattern 225. In some embodiments, densified pattern 225 can have a recess depth D1 that protrudes downward relative to the non-densified portions (e.g., left portion 221 and right portion 223). This can be such that at densified pattern 225, intermediate thickness T1 is less than first thickness T1. In some embodiments, recess depth D1 is less than the thickness of densified ePE substrate 220, resulting in a portion of the thickness remaining porous. In this embodiment, if densified pattern 225 has a recess depth, fine densified pattern 235 can have a recess depth D2. In some embodiments, recess depth D2 can be the same as recess depth D1. In other embodiments, recession depth D2 may be recessed further downward such that recession depth D2 is greater than recession depth D1. In a further embodiment, recession depth D2 can be recessed such that recession depth D2 is less than recession depth D1. In this further embodiment, the non-densified portions (e.g., left portion 221 and right portion 223) can function to recess more significantly than the densified portions (e.g., center portion 227) due to the higher porosity in the non-densified portions. The higher porosity of the non-densified portions can function to at least partially shrink during contraction.

[0071] In other embodiments, the densification pattern 225 can protrude or overhang outward relative to the non-densified portions (e.g., left portion 221 and right portion 223). This can be achieved by forming the densification pattern 225 as described above and then masking the densification pattern 225 in the densified portion 220 of the ePE substrate 210. This can be used, for example, in angioplasty balloons, where the balloon has a protruding densification pattern 225 to grip the blood vessel during deployment.

[0072] Figure 3 is a block diagram of a method 300 for densifying the expanded polyethylene (ePE) substrate of Figure 1, further comprising a molding step, according to some embodiments. Method 300 can be implemented in a variety of contexts, including, but not limited to, medical devices, including implantable medical devices. Method 300 includes multiple method steps, including step 310 of optionally providing an ePE substrate in a first size, step 320 of selectively densifying a portion of the ePE substrate, step 330 of shrinking the ePE substrate to a second size, and step 340 of molding the ePE substrate into an ePE article.

[0073] Optionally, method step 310 of providing an ePE substrate in a first size may be substantially similar to step 110 of providing an ePE substrate in a first size described above with respect to Figure 1. Method step 320 of selectively densifying a portion of an ePE substrate may be substantially similar to step 120 of selectively densifying a portion of an ePE substrate described above with respect to Figure 1. Method step 330 of shrinking an ePE substrate to a second size may be substantially similar to step 130 of shrinking an ePE substrate to a second size described above with respect to Figure 1.

[0074] In step 340, the ePE substrate is shaped into an ePE article, including, but not limited to, a tubular structure or a flattened structure. The ePE article can be shaped into or provided as a medical device or component of a medical device. The medical device can include an implantable medical device. The medical device can be used for long-term or short-term (e.g., temporary) implantation. The tubular structure can be implemented as, for example, a graft. The flattened structure can be implemented as, for example, a hernia patch, a cardiovascular patch, a nerve membrane, etc. The medical device can include a balloon (e.g., an angioplasty balloon, a urinary balloon, a stent deployment balloon) having a micro-densified pattern formed thereon, where the micro-densified pattern facilitates anchoring of the balloon to the patient's tissue, holding the balloon substantially in place and preventing device migration. In some embodiments, step 340 of forming the ePE substrate into an ePE article can be performed before step 320 of selectively densifying a portion of the ePE substrate, resulting in a selectively densified ePE article. In some embodiments, step 340 of forming the ePE substrate into an ePE article can be performed after the selective densification step but before step 330 of shrinking the ePE substrate to a second size, resulting in the ePE article being shrinked to the second size. In other embodiments, step 340 of forming the ePE substrate into an ePE article can be performed after step 330 of shrinking the ePE substrate to a second size, resulting in the ePE article being formed in the second size.

[0075] FIG. 4 is a diagram of an embodiment of forming a contracted ePE substrate 230 into a tubular ePE article 330 according to some embodiments. This diagram adds to the embodiment of FIGS. 2A and 2B . Forming the contracted ePE substrate 230 into a tubular ePE article 430 can further include wrapping the contracted ePE substrate 230 around a mandrel 410. The mandrel 410 can have a diameter D1. During wrapping around the mandrel 410, the contracted ePE substrates 230 can be joined or connected together by one of melt bonding, adhesive bonding, or mechanical fastening (i.e., using sutures) to form the tubular ePE article 430. In this embodiment, the smaller densified ePE substrate 235 is wrapped around the mandrel 410 with the micro-densification pattern oriented vertically. In other embodiments, the smaller densified ePE substrate 235 is wrapped around the mandrel 410 with the fine densified pattern 235 oriented transversely. The ePE article 430, which is a tubular structure, can be a medical device, including, but not limited to, an implantable graft.

[0076] 5 is a block diagram of a method 500 for generating a pattern on an expanded polyethylene (ePE) substrate, the method including providing, applying heat and pressure, and shrinking, according to some embodiments. Method 500 can be implemented in a variety of contexts, including, but not limited to, medical devices, which may include implantable medical devices.

[0077] In some embodiments, as shown in FIG. 5, a method 500 for generating a pattern on an ePE substrate optionally includes step 510 of providing an ePE substrate in a first size, step 520 of applying heat and pressure to the ePE substrate using a patterned member, and step 530 of shrinking the ePE substrate to a second size.

[0078] 5, optionally, in step 510, providing the ePE substrate in a first size, the ePE substrate also has a first density. The ePE substrate also has a first porosity. The first size can be defined by one or both of the longitudinal and lateral dimensions. The ePE substrate can be provided as a square, rectangular, or other shape.

[0079] With further reference to FIG. 5 , applying heat and pressure to the ePE substrate with a patterned member 520 can cause the patterned member to selectively densify the ePE substrate. Selective densification can be defined substantially similarly as described with respect to FIG. 1 . The heat and pressure can affect the extent to which the ePE substrate is densified (e.g., throughout the thickness of the ePE substrate), and the pattern of the patterned member can include points of densification (e.g., across the length of the ePE substrate). The patterned member can selectively densify a first portion of the ePE substrate to a second density, resulting in the ePE substrate having a first densification pattern in the first portion of the ePE substrate. In some embodiments, the second density can be greater than the first density. In some embodiments, the patterned member used to apply the heat and pressure is a mandrel. In some embodiments in which the patterned member is a mandrel, the mandrel can have a textured pattern (e.g., as shown in FIG. 6 ), and the first densification pattern is a corresponding textured pattern.

[0080] In some embodiments, applying heat and pressure to the ePE substrate with the patterned element 520 further includes contacting the ePE substrate with the patterned element at a temperature near the glass transition temperature or melting temperature of the densified ePE substrate, which may be from about 110°C to about 180°C. For example, the densified ePE substrate can be heated to a temperature of from about 110°C to about 120°C, from about 120°C to about 130°C, from about 130°C to about 140°C, from about 140°C to about 150°C, from about 150°C to about 160°C, from about 160°C to about 170°C, or from about 170°C to about 180°C. The element can be provided at any temperature suitable for producing the first densified pattern. The patterned element can be applied with a pressure greater than about 2 PSI. The applied pressure should be sufficient to avoid spreading or breaking the ePE substrate. The patterned feature can be applied at any pressure suitable for producing the first densified pattern. In some embodiments, the heat and pressure can be applied to the ePE substrate at a constant value. In other embodiments, the heat and pressure can be applied to the ePE substrate at a variable value to produce the first densified pattern.

[0081] The microstructure of the ePE substrate can be altered during step 520 of applying heat and pressure to the ePE substrate with the patterned member. For example, the microstructure of the ePE substrate can include a node and fibril structure, which can define a porous (e.g., microporous) structure. In some embodiments, the porosity of the microstructure can be reduced during step 520 of applying heat and pressure to the ePE substrate with the patterned member, while retaining some porosity and the node and fibril microstructure. In some embodiments, the density of the microstructure can remain substantially unchanged during step 520 of applying heat and pressure to the ePE substrate with the patterned member. In some embodiments, the application of heat and pressure can result in an at least partially densified microstructure, such that at least a portion of the node and fibril microstructure is densified and no longer defines a porous microstructure. In other embodiments, the ePE substrate can be fully densified, resulting in a fully densified microstructure.

[0082] Still referring to FIG. 5 , in some embodiments, step 530 of shrinking the ePE substrate to a second size is performed after step 520 of applying heat and pressure to the ePE substrate with the patterned member. In some embodiments, step 530 of shrinking the ePE substrate to a second size is performed such that the first densification pattern is reduced or shrunk in size to a second densification pattern having a series of features. In some embodiments, step 530 of shrinking the ePE substrate to a second size reduces the number of open spaces in the ePE substrate's microstructure. In some embodiments, the second densification pattern has the same shape as the first densification pattern. In this regard, the second densification pattern substantially retains the dimensional accuracy of the shape upon shrinking in size. In other embodiments, the second densification pattern has a slightly different shape than the first densification pattern. In still other embodiments, the second densification pattern may have a shape that is modified from the shape of the first densification pattern. In some embodiments, the first densification pattern includes a depth. This depth may be a recess depth (e.g., a depth protruding inward from the axis of the ePE substrate). The second densification pattern may retain the same depth as the first densification pattern upon shrinkage. However, the degree of depth of the first densification pattern may differ from the degree of depth of the second densification pattern. Alternatively, the depth of the second densification pattern may retain a ratio of the second depth to the axis of the ePE substrate, where the ratio of the second depth is substantially the same as the ratio of the first depth of the first densification pattern to the axis of the ePE substrate. In this regard, the second densification pattern retains its dimensional accuracy of depth upon size shrinkage. Furthermore, the first densification pattern covers a first surface area of ​​the ePE substrate. The second densification pattern may retain the same surface area coverage as the first densification pattern. In other words, the surface area ratio between the series of densified portions of the ePE substrate and the series of non-densified portions of the ePE substrate can be the same in the second densification pattern as in the first densification pattern.

[0083] Figure 6 is a side view of producing a pattern on an ePE substrate 610 according to the method of Figure 5, according to some embodiments. In Figure 6, an ePE substrate 610 is provided in alignment with a patterned feature 620. The patterned feature 620 includes a pattern 625. In this embodiment, the pattern is a triangular pattern 625 having raised regions 621 and recessed regions 623. However, other shapes for the pattern 625 are contemplated, including, but not limited to, rounded patterns, square patterns, rectangular patterns, etc.

[0084] Further to FIG. 6 , in this embodiment, ePE substrate 610 is shown in contact with patterned member 620. Applying heat and pressure 615 to patterned member 620 so that it contacts ePE substrate 610 compresses ePE substrate 610. In some embodiments, ePE substrate 610 becomes densified ePE substrate 630. In some embodiments, ePE substrate 610 is compliant such that densified ePE substrate 630 retains first densification pattern 635 when heat and pressure 615 is removed. In this regard, patterned member 620 can function to generate first densification pattern 635. In some embodiments, first densification pattern 635 can correspond to pattern 625 of patterned member 620. In some embodiments, first densification pattern 635 is a mirror image of pattern 625 of patterned member 620. In this embodiment, the first densification pattern 635 has first raised regions 631 and first recessed regions 633 that correspond to the raised regions 621 and recessed regions 623 of the pattern 625 .

[0085] Further to FIG. 6 , in some embodiments, after producing densified ePE substrate 630 having first densification pattern 635, densified ePE substrate 630 is shrunk in size to smaller densified ePE substrate 650. In some embodiments, smaller densified ePE substrate 650 includes second densification pattern 655. In some embodiments, the dimensions of first densification pattern 635 are reduced to second densification pattern 655. Second densification pattern 655 can retain the same shape or features as first densification pattern 635. In this embodiment, second densification pattern 655 includes second convex regions 651 and second concave regions 653. These regions correspond to first convex regions 631 and first concave regions 633, but are smaller in size. Furthermore, second densification pattern 655 has substantially the same depth ratio as first densification pattern 635. The second densified pattern 655 also maintains the same relative surface area coverage as the first densified pattern 635. In this regard, the second densified pattern 655 maintains its dimensional accuracy in both depth and shape upon shrinkage of the densified ePE substrate.

[0086] Figure 7 is a block diagram of a method 700 for generating a pattern on the ePE substrate of Figure 5, the method further including a molding step, according to some embodiments. Method 700 can be implemented in a variety of contexts, including but not limited to, medical devices, including implantable medical devices.

[0087] Method 700 optionally includes step 710 of providing an ePE substrate in a first size, step 720 of applying heat and pressure to the ePE substrate using a patterned member, step 730 of shrinking the ePE substrate to a second size, and step 740 of shaping the ePE substrate into an ePE article.

[0088] In some embodiments, method step 710 of optionally providing an ePE substrate in a first size may be substantially similar to step 510 of optionally providing an ePE substrate in a first size described above with respect to Figure 5. In some embodiments, method step 720 of applying heat and pressure to an ePE substrate with a patterned member may be substantially similar to step 520 of applying heat and pressure to an ePE substrate with a patterned member described above with respect to Figure 5. In some embodiments, method step 730 of shrinking an ePE substrate to a second size may be substantially similar to step 530 of shrinking an ePE substrate to a second size described above with respect to Figure 5.

[0089] Further to FIG. 7 , in step 740, the ePE substrate is shaped into an ePE article, which may include, but is not limited to, a tubular structure or a flattened structure. The ePE article may be shaped into or provided as a medical device or component of a medical device. The medical device or component of a medical device may be used for long-term or short-term implantation. The medical device may include an implantable medical device. The tubular structure may be implemented, for example, as a graft. The flattened structure may be implemented, for example, as a hernia patch, cardiovascular patch, nerve membrane, etc. The medical device may include a balloon (e.g., angioplasty balloon, urinary balloon, stent deployment balloon) having a micro-densified pattern formed thereon, where the micro-densified pattern facilitates anchoring of the balloon to the patient's tissue and holds the balloon substantially in place. In some embodiments, step 740 of forming the ePE substrate into an ePE article can be performed before step 720 of applying heat and pressure to the ePE substrate with a patterned member, resulting in a densification of a portion of the ePE article. In some embodiments, step 740 of forming the ePE substrate into an ePE article can be performed after the step of applying heat and pressure but before step 730 of shrinking the ePE substrate to a second size, resulting in the ePE article being shrunk to the second size. In other embodiments, step 740 of forming the ePE substrate into an ePE article can be performed after step 730 of shrinking the ePE substrate to a second size, resulting in the ePE article being formed at the second size. In some embodiments, step 740 of forming the ePE substrate into an ePE article is substantially similar to step 340 of forming the ePE substrate into an ePE article in FIG. 3 . In some embodiments, a mandrel can be used to form a tubular article from the densified ePE substrate, as shown in FIG. 4 .

[0090] 8A and 8B are illustrations of ePE articles 810, 820 having a densification pattern 815, according to some embodiments. FIG. 8A shows an ePE tubular article 810, and FIG. 8B shows an ePE flat article 820. Both the ePE tubular article 810 and the ePE flat article 820 include a micropattern 815. The pattern 815 may function substantially similarly to the microdensification pattern 235 of FIGS. 2A, 2B, and 4 and / or substantially similarly to the second densification pattern 655 of FIGS. 6 and 8. In this embodiment, the micropattern 815 is a densification pattern that has been shrunk to a reduced size.

[0091] In some embodiments, ePE tubular article 810 and ePE flat article 820 are made using a starting ePE substrate, which may be similar to ePE substrate 210 (FIGS. 2A and 2B) or ePE substrate 610 (FIG. 610). The starting ePE material is shaped into ePE articles. The ePE articles can include ePE tubular article 810 and ePE flat article 820. The ePE articles include a micropattern 815. The micropattern 815 can be formed by a selective densification patterning and shrinkage process, which can be substantially similar to one of the methods described in FIGS. 1, 3, 5, and / or 7.

[0092] In this embodiment, the micropattern 815 is a rounded pattern or a pattern of repeating rounded shapes. In other embodiments, the micropattern 815 can have different shapes, including, but not limited to, squares, triangles, or rectangles. In some embodiments, the micropattern 815 is a repeating pattern. In some embodiments, the micropattern 815 is a textured pattern. The textured pattern can include depth variations, where the depth variations include localized raised areas and localized depressed areas.

[0093] The micropattern 815 can impart a series of features to the ePE tubular article 810 and / or the ePE flat article 820. In some embodiments, the micropattern 815 is textured for anti-thrombogenic purposes. In some embodiments, the outer portions of the ePE articles 810, 820 are textured. In some embodiments, the inner portions of the ePE articles 810, 820 are textured. In some embodiments, if the ePE article is an ePE tubular article 810, the inner surface of the lumen of the ePE tubular article 810 can be textured for anti-thrombogenic purposes. In some embodiments, the texture of the micropattern 815 can attract cells for invasion. In some embodiments, the texture of the micropattern 815 can inhibit growth or invasion (e.g., thrombus growth) on the ePE articles 810, 820.

[0094] In some embodiments, the micropattern 815 is a textured surface configured to reduce friction and surface tension for better bonding. In some embodiments, the combination of a textured surface and retained porosity results in improved adhesion to another surface or device.

[0095] In some embodiments, the micropattern 815 is configured to promote tissue penetration. In some embodiments, this can be achieved by creating an increased surface area on the surface of the ePE article 810, 820. In some embodiments, the increased surface area is promoted by a textured surface or the micropattern 815.

[0096] In some embodiments, the micropattern 815 is configured to improve strength along the z-axis (e.g., along the thickness) of the ePE articles 810, 820. This can be achieved by selectively densifying the ePE articles 810, 820 and shrinking the ePE articles 810, 820 to create the micropattern 815. This can be improved by constraining the z-axis during processing. Improved strength in the z-axis also allows two or more ePE articles (e.g., articles 810, 820) to be joined together by at least one of collapsing and bonding.

[0097] In some embodiments, the micropattern 815 is configured to resist creep of the ePE articles 810,820.

[0098] In some embodiments, the micropattern 815 is configured to direct laminar flow across the surface of the ePE articles 810, 820. Directing laminar flow can include directing cells, fluids, or other materials within the body. In some embodiments, this includes promoting flow for antithrombogenic purposes, which can also result in improved scratch and abrasion resistance. Directing laminar flow can also configure the ePE articles 810, 820 to be antimicrobial. Directing laminar flow can be in any direction across the surface of the ePE articles 810, 820. Directing laminar flow can also be through the ePE articles 810, 820, for example, through the lumen of the ePE tubular article 910.

[0099] In some embodiments, the micropattern 815 is configured to promote tearing of the ePE articles 810, 820 along a propagation path. In some embodiments, the portion of the ePE article having the micropattern 815 may be tear-resistant. The portion of the ePE article without the micropattern 815 may not be tear-resistant, such that when a force is applied, the portion of the ePE article without the micropattern 815 will tear. The portion of the ePE article without the micropattern 815 can be selected to provide a propagation path for a tear to propagate through or across the ePE article. By providing a tear-resistant micropattern 815, the ePE articles 810, 820 can be selectively torn along a propagation path, which may have a predetermined shape. This feature allows for more precise control over the location of the tear in the ePE articles 810, 820. Tear promotion can also be used in devices with holes. For example, the micropattern 815 can be used to selectively tear the ePE article upon introduction of a suture. The portion of the ePE article surrounding the suture location may be tear-resistant, so that the suture is held in place and any holes created by the suture cannot propagate (e.g., act as an integral grommet).

[0100] In some embodiments, the ePE articles 810, 820 can expand horizontally, laterally, or radially. The ability to expand can come from contracting the ePE substrate to form an accumulated length. The ability to expand also allows for horizontal, lateral, or radial changes without adding additional mass or material to the ePE articles 810, 820.

[0101] In some embodiments, the micropattern 815 is a regular pattern. A regular pattern may be a single repeating shape or a series of repeating shapes. In other embodiments, the micropattern 815 is an irregular pattern. An irregular pattern may not have repeating shapes and may be a random pattern.

[0102] In some embodiments, the micropattern 815 can provide a unique feel or texture. In some embodiments, the micropattern 815 can improve moisture wicking. In some embodiments, the micropattern 815 can provide an antimicrobial surface. These features can be found in textile-related embodiments.

[0103] In some embodiments, the micropattern 815 is useful for preventing device migration. In long-term implants (e.g., stent grafts), the texture from the micropattern 815 can increase the force required to displace the long-term implant while also providing a surface for enhanced tissue adhesion. In temporary implants (e.g., angioplasty or urinary balloons), the texture from the micro-densified pattern 815 can also be useful for stabilizing the temporary implant while reducing tissue adhesion to facilitate eventual device removal.

[0104] While specific embodiments are provided herein, it is understood that different configurations and material properties can be selected and processed within the spirit of this disclosure. Additionally, specific embodiments provide for temperatures, processes, and properties that can be varied while still falling within the spirit of this disclosure.

[0105] The disclosure of this application has been described above both generically and with reference to specific embodiments. It will be apparent to those skilled in the art that various modifications and changes may be made to the embodiments without departing from the scope of the present disclosure. Accordingly, it is intended that the embodiments encompass modifications and variations of the present disclosure and their equivalents, provided they fall within the scope of the appended claims.

Claims

1. 1. A method for densifying an expanded polyethylene (ePE) substrate, the method comprising: selectively densifying a portion of an ePE substrate to form a densified portion of the ePE substrate, the ePE substrate having a first density and a first size, the densified portion of the ePE substrate having a second density greater than the first density, and the densified portion of the ePE substrate having a densified pattern; reducing the densified pattern to a fine densified pattern by shrinking the ePE substrate to a second size, the second size being smaller than the first size and the fine densified pattern being smaller than the densified pattern; A method comprising:

2. The method of claim 1 , wherein the step of selectively densifying portions of the ePE substrate is performed by embossing.

3. The method of claim 1 , wherein selectively densifying a portion of the ePE substrate further comprises applying heat and pressure to the ePE substrate.

4. The method of claim 3, wherein the step of applying heat and pressure to the ePE substrate comprises contacting the ePE substrate with a member at about 110°C to about 180°C.

5. The method of claim 1 further comprising forming the ePE substrate into an ePE article.

6. The method of claim 5 , wherein the ePE substrate is formed into a medical device.

7. The method of claim 6 , wherein the medical device comprises an implantable medical device.

8. The method of claim 1 , wherein shrinking the ePE substrate to a second size further comprises applying heat to the ePE substrate.

9. The method of claim 1 , wherein the shape of the fine densification pattern is the same as the shape of the densification pattern.

10. The method of claim 1 , wherein the micro-densified pattern is configured to promote tissue infiltration.

11. The method of claim 1 , wherein the micro-densified pattern is configured for anti-thrombogenicity.

12. The method of claim 1 , wherein the fine densification pattern is configured to direct laminar flow across a surface of the fine densification pattern.

13. 1. A method for producing a pattern on an oriented polyethylene (ePE) substrate, the method comprising: applying heat and pressure to an ePE substrate using a patterned member, the ePE substrate having a first density and a first size, and selectively densifying a first portion of the ePE substrate to a second density with the patterned member, such that the ePE substrate has a first densification pattern in the first portion of the ePE substrate; shrinking the ePE substrate to a second size, thereby reducing the first densification pattern to a second densification pattern having a series of features, the second densification pattern being smaller than the first densification pattern; A method comprising:

14. The method of claim 13 , wherein the patterned member used to apply heat and pressure is a mandrel.

15. The method of claim 14 , wherein the mandrel has a textured pattern and the first densification pattern is a corresponding textured pattern.

16. The method of claim 13, wherein applying heat and pressure to the ePE substrate comprises contacting the ePE substrate with the patterned feature at about 110°C to about 180°C.

17. 14. The method of claim 13, wherein the first densification pattern comprises a first depth ratio and the second densification pattern comprises a second depth ratio, and the first depth ratio and the second depth ratio are substantially the same.

18. An article of expanded polyethylene (ePE), said article comprising: An article comprising an ePE substrate formed into an ePE article, said ePE article comprising a micropattern, said micropattern being formed by a selective densification patterning and shrinkage process.

19. 20. The article of claim 18, wherein the micropattern is textured for anti-thrombogenic purposes.

20. 20. The article of claim 18, wherein the micropattern is configured to promote tissue infiltration.

21. 20. The article of claim 18, wherein the micropattern is configured to direct laminar flow across the surface of the ePE article.

22. 20. The article of claim 18, wherein the micropattern is configured to promote tearing of the ePE article along a propagation path.

23. 20. The article of claim 18, wherein the micropattern is configured to promote migration resistance.

24. 20. The article of claim 18, wherein the micropattern comprises one repeating shape.

25. 20. The article of claim 18, wherein the micropattern is a random pattern.

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