Stretchable conductive articles including a polymeric substrate with a pattern of slits and methods of making same

Abstract

The present disclosure provides a stretchable conductive article. The stretchable conductive article includes a substrate configured to have a planar unstretched state and a non-planar deformed stretched state. When the substrate is in the planar unstretched state the substrate includes a sheet comprising a first major surface, a second major surface opposite the first major surface, and a plurality of slits that each extend from the first major surface to the second major surface. The plurality of slits is arranged in a Kirigami pattern, which includes at least one feature that is smaller than 500 micrometers. The article is electrically conductive. Additionally, a method is provided, including forming a plurality of slits in a substrate using a microstructured cutting tool.

Description

PA102608W002STRETCHABLE CONDUCTIVE ARTICLES INCLUDING A POLYMERIC SUBSTRATE WITH A PATTERN OF SLITS AND METHODS OF MAKING SAMEField

[0001] The present disclosure relates generally to tension-activated, expanding conductive articles.Summary

[0002] In a first aspect, a stretchable conductive article is provided. The stretchable conductive article comprises a substrate configured to have a planar unstretched state and a non-planar deformed stretched state. When the substrate is in the planar unstretched state the substrate comprises a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface. The plurality of slits is arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers. The article is electrically conductive.

[0003] In a second aspect, a method of making a stretchable conductive article is provided. The method comprises forming a plurality of slits in a substrate using a microstructured cutting tool, thereby forming a substrate configured to have a planar unstretched state and a non-planar deformed stretched state. When the substrate is in the planar unstretched state the substrate comprises a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface. The plurality of slits is arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers. The article is electrically conductive.Brief Description of Drawings

[0004] FIG. 1 A is a top view schematic drawing of an exemplary double slit pattern.

[0005] FIG. IB is a top view schematic drawing of the primary tension lines of the double slit pattern shown in FIG. 1 A when exposed to tension.

[0006] FIG. 1C is a top view schematic drawing of another exemplary double slit pattern.

[0007] FIG. ID is an image of a modeled exemplary stretchable conductive article having a double slit pattern, in the process of being stretched into a non-planar deformed stretched state.

[0008] FIG. IE is a scanning electron microscopy (SEM) image of a portion of the exemplary stretchable conductive article of Example 1, having a double slit pattern, in a planar unstretched state.

[0009] FIG. IF is an SEM image of a portion of the exemplary stretchable conductive article of Example 1, having a double slit pattern, in a non-planar deformed stretched state.

[0010] FIG. 2A is a top view schematic drawing of an exemplary double slit triple beam pattern.

[0011] FIG. 2B is a nearly side view drawing from a photograph of a material into which the slit pattern of FIG. 2B has been formed after it has been stretched into a non-planar deformed stretched state.

[0012] FIG. 2C is a top view schematic drawing of another exemplary double slit triple beam pattern.

[0013] FIG. 2D is a close-up top view schematic drawing of four adjacent slits in the pattern of FIG. 2C.

[0014] FIG. 2E is an image of a modeled exemplary stretchable conductive article having a double slit triple beam pattern, in the process of being stretched into a non-planar deformed stretched state.

[0015] FIG. 2F is an SEM image of a portion of the exemplary stretchable conductive article of Example 3, having a double slit triple beam pattern, in a planar unstretched state.

[0016] FIG. 2G is an SEM of a portion of the exemplary stretchable conductive article of Example 3, having a double slit triple beam pattern, in a partially non-planar deformed stretched state.

[0017] FIG. 2H is an SEM of a portion of the exemplary stretchable conductive article of Example 3, having a double slit triple beam pattern, in a non-planar deformed stretched state.

[0018] FIG. 3 A is a top view schematic drawing of an exemplary double slit double beam pattern.

[0019] FIG. 3B is a close-up top view schematic drawing of three adjacent slits in the pattern of FIG.3A.

[0020] FIG. 3 C is an image of a modeled exemplary stretchable conductive article having a double slit double beam pattern, in the process of being stretched into a non-planar deformed stretched state.

[0021] FIG. 3D is an SEM image of a portion of the exemplary stretchable conductive article of Example 2, having a double slit double beam pattern, in a planar unstretched state.

[0022] FIG. 3E is an SEM image of a portion of the exemplary stretchable conductive article of Example 2, having a double slit double beam pattern, in a non-planar deformed stretched state.

[0023] FIG. 4 is a top view schematic drawing of an exemplary single slit pattern.

[0024] FIG. 5A is a generalized schematic side view of a cut polymeric substrate in a planar unstretched state, for use in making an exemplary stretchable conductive article.

[0025] FIG. 5B is a generalized schematic side view of the cut polymeric substrate of FIG. 5 A having a first metal coating deposited thereon, in a planar unstretched state, and also a generalized schematic side view of the coated substrate in a non-planar deformed stretched state.

[0026] FIG. 5C is a generalized schematic side view of the coated substrate of FIG. 5B in a planar unstretched state having a second metal coating deposited on the first metal coating, and also a generalized schematic side view of the twice-coated substrate in a non-planar deformed stretched state.

[0027] FIG. 5D is an SEM image of a portion of the exemplary stretchable conductive article of Example 7, having two metal coatings on a polymeric substrate.

[0028] FIG. 5E is a photograph of a portion of the exemplary stretchable conductive article of Example 6, having a double slit double beam pattern and a first copper coating deposited on a polymeric substrate, in a planar unstretched state.

[0029] FIG. 5F is a photograph of a portion of the exemplary stretchable conductive article of Example 6, in a non-planar deformed stretched state.

[0030] FIG. 5 G is an SEM image of a portion of the exemplary stretchable conductive article of Example 6, in a non-planar deformed stretched state.

[0031] FIG. 5H is a photograph of a portion of the exemplary stretchable conductive article of Example 8, having a single slit pattern and a first copper coating deposited on a polymeric substrate, in a planar unstretched state.

[0032] FIG. 51 is a photograph of a portion of the exemplary stretchable conductive article of Example 8, in a non-planar deformed stretched state.

[0033] FIG. 5 J is an SEM image of a portion of the exemplary stretchable conductive article of Example 8, in a non-planar deformed stretched state.

[0034] FIG. 6A is an SEM image of a portion of an exemplary stretchable conductive article including a metal substrate having a double slit double beam pattern and an adhesive disposed on a major surface of the metal substrate, in a planar unstretched state.

[0035] FIG. 6B is an SEM image of a portion of the exemplary stretchable conductive article of FIG. 6 A, in a partially non-planar deformed stretched state.

[0036] FIG. 6C is an SEM image of a portion of the exemplary stretchable conductive article of FIG. 6B at a lower magnification.

[0037] FIG. 6D is a photograph of a portion of the exemplary stretchable conductive article of FIG. 6 A, including a metal substrate and an adhesive disposed on a major surface of the metal substrate, in a non-planar deformed stretched state.

[0038] FIG. 7A is a photograph of a portion of the exemplary stretchable conductive article of Example 9, including a metal substrate having a double slit triple beam pattern disposed between two layers, in a planar unstretched state.

[0039] FIG. 7B is a photograph of a portion of the exemplary stretchable conductive article of FIG. 7 A, in a partially non-planar deformed stretched state.

[0040] FIG. 7C is a generalized schematic cross-sectional view of an exemplary stretchable conductive article including a cut metal substrate disposed between two layers.

[0041] FIG. 8A is a photograph of the proof of concept stretchable conductive article of Example 4, including a metal substrate embedded in an adhesive, in a non-planar deformed stretched state.

[0042] FIG. 8B is a photograph of the exemplary stretchable conductive article of Example 5, including a metal substrate embedded in an adhesive, in a non-planar deformed stretched state.

[0043] FIG. 9 is a generalized schematic side view of an apparatus for use in making an exemplary stretchable conductive article.

[0044] FIG. 10 is a generalized schematic side view of another apparatus for use in making an exemplary stretchable conductive article.

[0045] FIG. 11 is a generalized schematic side view of an additional apparatus for use in making an exemplary stretchable conductive article.

[0046] FIG. 12 is a generalized schematic side view of a further apparatus for use in making an exemplary stretchable conductive article.

[0047] FIG. 13A is a photograph of a roll of the exemplary stretchable conductive article of Example 10 including a polymeric substrate with a metal coating on a first major surface of the polymeric substrate, having a single slit double beam pattern, in an unstretched state.

[0048] FIG. 13B is an SEM image of a portion of the exemplary stretchable conductive article of FIG.13 A, in an unrolled and non-planar deformed stretched state.

[0049] Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.Detailed Description

[0050] The terms “a”, “an”, “the”, “at least one”, and “one or more” are used interchangeably.

[0051] The term “and / or” means one or both such as in the expression A and / or B refers to A alone, B alone, or to both A and B.

[0052] The term “essentially” means 95% or more.

[0053] The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as same, equal, uniform, constant, strictly, and the like, are understood to be within the usual tolerances or measuring error applicable to the specific circumstance rather than requiring absolute precision or a perfect match. Each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0054] As used herein, “adjacent” means next to or adjoining.

[0055] The term “electrically conductive” means a material that allows an electric current to travel through it.

[0056] As used herein, “polymeric” refers to a material prepared from at least one monomer (such as a homopolymer) or to material prepared from two or more monomers (such as a copolymer, a terpolymer, or the like).

[0057] The terms “sheet” and “film” generally refer to a material with a very high ratio of length or width to thickness. A sheet or film has two major surfaces defined by a length and a width.

[0058] The term “layer” generally refers to a thickness of material that has a relatively consistent chemical composition.

[0059] The term “substrate” encompasses sheets, films, layers, and articles.

[0060] As used herein, “thickness” refers to the smallest dimension of a substrate or an article, e.g., in a z-axis while a major surface of the substrate or the article is in the x- and y-axes. Thickness may be determined using a micrometer gauge or doing a microscopic analysis of a cross-sectional sample of a substrate or an article.

[0061] The term “planar” with respect to a substrate or article refers to a substrate or article that defines a plane, a longitudinal axis extending along a length of the substrate or article, a transverse axis disposed in the plane and extending perpendicular to the longitudinal axis, and a thickness normal to the plane.

[0062] The term “Kirigami pattern” refers to a pattern of a plurality of slits cut through the thickness of a substrate.

[0063] The term “stretchable” means a substrate or article whose length may be expanded under tension without tearing of the substrate or an article. The presence of a Kirigami pattern of slits may enable an otherwise non-stretchable substrate or article to become stretchable.

[0064] As used herein, “slit” means a cut through a thickness of a substrate or an article.

[0065] The term “resin” refers to a particulate or viscous liquid polymeric material.

[0066] The term “pressure-sensitive adhesive” or “PSA” is used in its conventional manner according to the Pressure-Sensitive Tape Council, which states that pressure-sensitive adhesives are known to possess properties including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be removed cleanly from the adherend. Materials that have been found to function well as PSAs include polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power. PSAs are characterized by being normally tacky at room temperature (e.g., 20°C). Central to all PSAs is a desired balance of adhesion and cohesion that is often achieved by optimizing the physical properties of the elastomer, such as glass transition temperature and modulus. For example, if the glass transition temperature (Tg) or modulus of the elastomer is too high and above the Dahlquist criterion for tack (storage modulus of 3 x 106dynes / cm2at room temperature and oscillation frequency of 1 Hz), the material will not be tacky and is not useful by itself as a PSA material.

[0067] Stretchable Conductive Articles

[0068] In a first aspect, a stretchable conductive article is provided. The stretchable conductive article comprises:

[0069] a substrate configured to have a planar unstretched state and a non-planar deformed stretched state, wherein when the substrate is in the planar unstretched state the substrate comprises:

[0070] a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface, the plurality of slits being arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers, and

[0071] wherein the article is electrically conductive.

[0072] It has been discovered that it is possible to provide advanced materials and / or devices with unique properties by creating intricate patterns of cuts in a substrate at a microscopic scale (e.g., micro-kirigami pattern). For instance, electrically conductive adhesives, flexible electronics or interconnects, etc., can be made with stretchable conductive articles according to at least certain embodiments of the present disclosure. Optionally, the stretchable conductive article has a form of a roll, which allows sections to be cut from an article having indefinite length.

[0073] In some embodiments, suitable Kirigami patterns include single unidirectional patterns or multislit unidirectional patterns.

[0074] A “slit” is defined herein as a narrow cut through the article forming at least one line, which may be straight or curved, having at least two terminal ends. Slits described herein are discrete, meaning that individuals slits do not intersect other slits. A slit is generally not a cut-out, where a “cut-out” is defined as a surface area of the sheet that is removed from the sheet when a slit intersects itself. However, in practice, many forming techniques result in the removal of some surface area of the sheet that is not considered a “cut-out” for the purposes of the present application. In particular, many cutting technologies produce a “kerf”, or a cut having some physical width.

[0075] As used herein, the term “single slit pattern” refers to a pattern of individual slits that form individual rows each extending across the sheet transversely, where the rows form a repeating pattern of individual rows along the axial length of the sheet, and the pattern of slits in each row is different than the pattern of slits in the directly adjacent rows. For example, the slits in one row may be axially offset or out of phase with the slits in the directly adjacent rows.

[0076] The term “multi-slit pattern” is defined herein as a pattern of individual slits that form a first set of adjacent rows across the transverse direction y of the sheet, where the individual slits within the first set of adjacent rows are aligned in the transverse direction y . In a multi-slit pattern, the first set of adjacent rows form a repeating pattern with at least a second row along the axial length of the sheet, where the slits in the first set of adjacent identical rows are offset from the slits in the next row in the transverse direction y. The term "multi-slit pattern" includes double slit patterns, triple slit patterns, quadruple slit patterns, etc.

[0077] As used herein, the term “double slit pattern” refers to a pattern of a plurality of individual slits. The pattern includes a plurality of rows of slits and the individual slits in a first row are substantially aligned with the individual slits in a directly adjacent, second row. A double slit is comprised of a slit in a first row that is substantially aligned with a slit in a second row. A double slit pattern includes at least two sets of double slit rows that are offset from each other in the transverse axis.

[0078] As used herein, the term “triple slit pattern” refers to refers to a pattern of a plurality of individual slits. The pattern includes a plurality of rows of slits and the individual slits in a first row are substantially aligned with the individual slits in a directly adjacent, second row. The slits in the second row are substantially aligned with the individual slits in a directly adjacent, third row. A triple slit is comprised of a slit in a first row that is substantially aligned with a slit in a second row, both of which are substantially aligned with a slit in a third row. Together, these three substantially aligned slits form a triple slit. A triple slit pattern includes at least two sets of triple slit rows that are offset from each other in the transverse axis.

[0079] As used herein, the term “quadruple slit pattern” refers to refers to a pattern of a plurality of individual slits. The pattern includes a plurality of rows of slits and the individual slits in a first row are substantially aligned with the individual slits in a directly adjacent, second row. The slits in the second row are substantially aligned with the individual slits in a directly adjacent, third row. The slits in the third row are substantially aligned with the individual slits in a directly adjacent, fourth row. A quadruple slit is comprised of a slit in a first row that is substantially aligned with a slit in a second row, both ofwhich are substantially aligned with a slit in a third row, all three of which are substantially aligned with a slit in a fourth row. Together, these four substantially aligned slits form a quadruple slit. A quadruple slit pattern includes at least two sets of quadruple slit rows that are offset from each other in the transverse axis.

[0080] The term “multi-slit pattern” includes double slit patterns, triple slit patterns, quadruple slit patterns, etc. Further, the term “multi-slit pattern” is meant to include any slit pattern wherein two or more slits that are each in different, directly adjacent rows substantially align with one another such that their terminal ends substantially align. Substantial alignment of the terminal ends of aligned multi-slits means that if you draw an imaginary line between two aligned terminal ends in two adjacent slits of the multi-slit, the angle of that imaginary line relative to the alignment axis (the axis that is perpendicular to the row(s)) is no greater than + / - 20 degrees. In some embodiments, the length of each slit that forms a multi-slit differs by no more than + / -20% of the total length of the longest or shortest slit. In some embodiments, where the slits are linear, they are substantially parallel to one another. In some embodiments where the slits are not linear, the aligned multi-slits are all substantially aligned parallel to the tension axis within + / - 20 degrees.

[0081] The midpoint 132 of a section of transverse beam 130 can be referred to as the geometric center of that section of the transverse beam (as shown in FIG. 1 A). In some embodiments, the individual slits in a row are substantially aligned with the individual slits in more than one and less than a million directly adjacent rows. In some embodiments, the slits are substantially perpendicular to the tension axis (T).

[0082] Double, triple, quadruple, or multi-slit patterns create significantly more out of plane undulation than single slit patterns when exposed to tension along a tension axis. This out of plane undulation of the material has great value for many applications.

[0083] When used herein with respect to single slit patterns and multi-slit patterns (defined above), the term “multibeam slits” is defined as one or more simple slits (in addition to the slits forming the single slit or multi-slit pattern) formed between two adjacent slits, where the two adjacent slits are either in the same row or adjacent rows. For instance, “single beam”, “double beam” or “triple beam” variations of the double slit pattern.

[0084] In FIG. 1, a schematic drawing is provided of an exemplary double slit pattern. The pattern 100 includes a plurality of slits 110 in rows of slits 112. Each slit 110 includes a midpoint 118 between a first terminal end 114 and a second terminal end 116. A first row 112a of slits 110 and a second row 112b of slits 110 each include a plurality of slits 110 that are spaced from one another. The axial space between directly adjacent slits 110 in a row 112 in combination with the adjacent portions of the transverse beam 130 can form an axial beam 120 between adjacent slits 110 in a row 112. In the exemplary embodiment of FIG. 1A, a straight, imaginary line extends between and connects terminal ends 114, 116. In this exemplary embodiment, the straight, imaginary line extending between and connecting the terminal ends of a first slit is substantially colinear with the straight, imaginary line extending between and connecting the terminal ends of a directly adjacent second slit in the same row. In this exemplary embodiment, all ofthe straight, imaginary lines extending between and connecting the slit terminal ends in a single row are approximately colinear.

[0085] Together, rows 112a, 112b of slits 110 form a transverse beam 130. Transverse beam 130 is bound in the axial direction by slits 110. An overlap beam 136 is directly adjacent to and, in this embodiment, on both sides of each transverse beam 130. Overlap beam 136 is bound in the axial direction by non-aligned slits. The slits in each directly adjacent row 112a, 112b that forms an edge or side of transverse beam 130 are substantially aligned with one another such that they are substantially parallel and their terminal ends 114, 116 are substantially aligned perpendicular to the axis of the row and equidistant to one another. In some embodiments, the slits that are aligned have substantially the same slit length and pitch (pitch being relative to the tension axis).

[0086] Each section of transverse beam 130 bordered by two parallel and substantially aligned slits 110 includes a midpoint 132 that is (1) at the midpoint (transversely) between first terminal end 114 and a second terminal end 116 of the slits 110 that form the sides of transverse beam 130 and (2) at the midpoint (axially) between the two slits 110 that form the sides of transverse beam 130. A midpoint 132a of a first section of transverse beam 130a is out of phase with a midpoint 132b of the directly adjacent section of the directly adjacent transverse beam 130b. In the embodiment of FIG. 1A, the midpoint 132a of a first section of transverse beam 130a substantially aligns axially with midpoint 132c of a first section of transverse beam 130c, which is the second directly adjacent transverse beam from transverse beam 130a.

[0087] FIG. 1 A also shows the tension axis (T) which is substantially parallel to the axial direction and substantially perpendicular to the transverse direction, and the direction of the rows of slits, in the embodiment of FIG. 1A. The tension axis (T) is an axis along which tension can be provided to deploy the material into which the pattern 100 has been formed, which creates the upward and downward movement of transverse beams 130 and rotation of overlap beams 136.

[0088] FIG. IB shows the primary tension lines 140 (e.g., the lines approximating the highest tensile stress path) formed when an article including the slit pattern of FIG. 1 A is deployed with tension along the tension axis T. FIG. IB shows in dashed lines the primary tension lines 140, which are where the greatest tensile stress will occur. Tension lines are imaginary paths through the material that carry the greatest load when tension is applied to the material along the tension axis. When tension is applied along tension axis (T), the primary tension lines 140 move more closely into alignment with the applied tension axis, causing the sheet to distort. When multi-slit patterns are deployed, the activation of tension along the primary tension lines 140 causes substantially all regions of the pattern to experience some tension or compression (tensile stress or compressing stress) and then many of the regions buckle and bend out of the plane of the original two-dimensional film.

[0089] When tension is applied to a material, sheet, or film including a double slit pattern, the portions of the transverse beam 130 between pairs of aligned slits 110 experience primarily compressive stress, which causes the beam 130 to buckle out of the original plane of the sheet forming an undulation or a loop shape, while staying nominally parallel to the tension axis. Overlap beams 136 buckle and bend outof the plane of the original material or sheet as they experience these tensile forces. In the transverse beams 130 only the region between the pairs of slits, called the axial beam 120, experiences the tension (and tensile stress) and transmits it to the next row 112 of slits 110. The axial beam 120 between directly adjacent slits 110 in a single row 112 in combination with the adjacent portions of the transverse beam 130 is marked with dashed lines on the edges where the greatest stress occurs. These tension bearing regions remain relatively flat and parallel to the pretensioned plane of the material or sheet when tension is applied. These tension bearing regions do not to rotate because the tension lines through them are substantially parallel to the primary tension axis (T).

[0090] Referring to FIG. 1C, a schematic drawing is provided of another exemplary double slit pattern 100c. The main difference between the double slit pattern of FIG. 1C and the double slit pattern of FIG.1 A is that there is less overlap between the ends of adjacent pairs of slits 110, which results in longer transverse beams 130 and wider axial beams 120 than in the double slit pattern of FIG. 1A. FIG. 1C also shows the tension axis (T) which is substantially parallel to the axial direction and substantially perpendicular to the transverse direction, and the direction of the rows of slits, in the embodiment of FIG.1C.

[0091] FIG. ID provides an image of a modeled exemplary stretchable conductive article lOOd having a double slit pattern, in the process of being stretched into a non-planar deformed stretched state.

[0092] Referring to FIG. IE, a scanning electron microscopy (SEM) image is provided of a portion of an exemplary stretchable conductive article lOOe having a double slit pattern as shown in FIG. 1C, in a planar unstretched state in a non-planar deformed stretched state. This stretchable conductive article lOOe was made according to Example 1 described in detail below. Four adjacent slits 110 are indicated in the SEM image.

[0093] FIG. IF provides an SEM image of a portion of an exemplary stretchable conductive article lOOf having a double slit pattern, in a non-planar deformed stretched state. This stretchable conductive article lOOf is also of Example 1 described below. Each of an axial beam 120, a transverse beam 130, and an overlap beam 136 are indicated in the SEM image.

[0094] FIG. 2A is a top view schematic drawing of an exemplary double slit triple beam pattern. The beam region, and more specifically the direct path between the closest terminal ends of two adjacent slits in adjacent rows such as ends 216a and 214a of FIG. 2A, experiences the highest concentration of forces when tension is applied to a single slit patterned material. As such, these beam regions experience the greatest stress concentration during deployment (or tension application or activation) of the material. This high stress concentration can result in tearing of the material during deployment. Additional slits added in this region that cross through the direct path between closest terminal ends in adjacent rows can create one or more additional force-carrying paths, or additional beams, which have additional stress concentrating terminal ends that can increase the maximum force bearing capacity of the material.Materials or articles that include multibeam slit patterns have a greater maximum tension force as compared to a material or article with the same pattern of beams but without multibeams. As used herein, the term “maximum tension force” refers to the maximum tensile force that can be applied to a sample ofslit-patterned material before it tears. Generally, the maximum tension force occurs just before a slit-patterned material tears. A test method for measuring the maximum tension force is described in U. S. Patent Application No. 62 / 953042, assigned to the present assignee, the entirety of which is incorporated by reference herein. The Maximum Tension Force (e.g., tear force), is the maximum force measured by the load frame as the sample is stretched. This is typically just before the material begins to tear. In some embodiments, materials or articles that include a multibeam slit pattern are capable of withstanding larger tension forces without tearing as compared to a material or article with the same pattern except without multibeams.

[0095] In some embodiments, materials or articles with multibeam slit patterns have the same or lower deployment force. As used herein, the term “deployment force” refers to the force required to substantially deploy the patterned sheet.

[0096] In some embodiments, it is advantageous to have the maximum tension force (the tension force required to tear the slit patterned material during deployment or tensioning along tension axis T) be greater than the deploy force (the force required to deploy the sample). The Max-Deploy Ratio is the ratio of the maximum tension force divided by the deploy force. In some embodiments, it is advantageous for that ratio to be as large as possible such that the force applied to deploy a patterned sheet is much lower than the maximum force that the sheet can sustain. This prevents users of the sheet from accidentally tearing the material when deploying it.

[0097] Multibeam slits 280 are formed in overlap beam 236. These multibeam slits 280 will enable the formation of multibeams 282 when material 200 is exposed to tension along the tension axis. The multibeam slits 280, and the resulting multibeams 282, of FIGS. 2A and 2B are substantially linear.

[0098] Those of skill in the art will appreciate that many changes may be made to the pattern while still falling within the scope of the present disclosure. In some embodiments, multi-slit pattern will be a triple slit, quadruple slit, or other multi-slit instead of a double slit pattern. Alternatively, the slit length, slit size, slit thickness, slit shape, row size or shape, transverse beam size or shape, and / or overlap beam size or shape can vary. Further, the degrees of offset or phase offset can vary from what is shown. The slit, row, or beam pitch can vary. The angle between the tension axis and slits can vary. The number, shape, size, etc. of the multibeam slits and / or multibeams can vary. Alternatively, the row size or shape and beam size or shape can vary. Further, the degrees of offset or phase offset can vary from what is shown. Many of these changes could change the deployment pattern.

[0099] FIG. 2B is a drawing created from a photograph of a material including the slit pattern of FIG.2A when exposed to tension along tension axis T. When material 200 is tension activated or deployed along tension axis T, portions of material 200 experience tension and / or compression that causes material 200 to move out of the original plane of material 200 in its non-tensioned format. Portions of transverse beams 230 undulate out of the original plane of the material 200 in its pretensioned state (FIG. 2A) forming loops, while staying nominally parallel to the tension axis. The axial beam 220 between adjacent slits 210 in a row 212 and adjacent portion of transverse beam 230 stays substantially parallel to the original plane of material 200 in its pretensioned state (FIG. 2A). Overlap beams 236 buckle and rotateout of the plane of the original material or sheet. Because of the addition of two multibeam slits 280, each overlap beam 236 is cut into three distinct multibeams 282 that each carry tension and stay nominally parallel to each other and move or rotate as a group. The motion of the overlap beams 236 in combination with the undulation of the transverse beams 230 creates open portions 222.

[0100] When the tension-activated material 200 is wrapped around an article or placed directly adjacent to itself, the loops and undulations interlock with one another and / or opening portions 222, to create an interlocking structure. Additional multi-slit patterns are shown in, for example, U.S. Patent Application No. 62 / 952806, assigned to the present assignee, the entirety of which is incorporated herein.

[0101] Referring to FIG. 2C, a schematic drawing is provided of another exemplary double slit triple beam pattern 200c. The main difference between the double slit triple beam pattern of FIG. 2C and the double slit triple beam pattern of FIG. 2 A is that there are more axial beams 120 than in the pattern of FIG. 2A. FIG. 2C also shows the tension axis (T) which is substantially parallel to the axial direction and substantially perpendicular to the transverse direction, and the direction of the rows of slits, in the embodiment of FIG. 2C. FIG. 2D is a close-up top view schematic drawing of four adjacent slits (two slits 210 and two multi-beam sins 280) in the pattern of FIG. 2C.

[0102] FIG. 2E provides an image of a modeled exemplary stretchable conductive article 200e having a double slit triple beam pattern, in the process of being stretched into a non-planar deformed stretched state.

[0103] Referring to FIG. 2F, an SEM image is provided of a portion of an exemplary stretchable conductive article 200f having a double slit triple beam pattern as shown in FIG. 2C, in a planar unstretched state. This stretchable conductive article 200f was made according to Example 3 described in detail below. Four slits (two slits 210 and two multi-beam slits 280) are indicated in the SEM image.

[0104] FIG. 2G provides an SEM image is provided of a portion of an exemplary stretchable conductive article 200g having a double slit triple beam pattern as shown in FIG. 2C, in a partially non-planar deformed stretched state. This stretchable conductive article 200g is also of Example 3 described below. Each of a transverse beam 230, an axial beam 220, and a few multibeams 282 are indicated in the SEM image.

[0105] FIG. 2H is an SEM image of another exemplary stretchable conductive article 200h having a double slit triple beam pattern, in a non-planar deformed stretched state, with each of a transverse beam 230, an axial beam 220, and a few multibeams 282 indicated in the SEM image. This stretchable conductive article 200h is also of Example 3 described below.

[0106] In some embodiments, a stretchable conductive article has a double slit double beam pattern. FIG. 3 A is a top view schematic drawing of an exemplary double slit double beam pattern 300a. The double slit double beam pattern 300a differs from the double slit triple beam patterns described in detail above in having three adjacent slits (two slits 10 and one multi-beam slit 380) instead of four adjacent slits (e.g., two slits 210 and two multi-beam slits 280 in FIGS. 2A, 2C, and 2D). A transverse beam 330 and an axial beam 320 are each indicated in the drawing of the double slit double beam pattern 300a. FIG. 3B is a close-up top view schematic drawing of three adjacent slits 380 in the pattern of FIG. 3 A.

[0107] FIG. 3C is an image of a modeled exemplary stretchable conductive article 300c having a double slit double beam pattern, in the process of being stretched into a non-planar deformed stretched state.

[0108] FIG. 3D is an SEM image of a portion of an exemplary stretchable conductive article 300d having a double slit double beam pattern as shown in FIG. 3C, in a planar unstretched state. This stretchable conductive article 300d was made according to Example 2 described in detail below. Three slits (two slits 10 and one multi-beam sin 280) are indicated in the SEM image.

[0109] Referring to FIG. 3E, an SEM image is provided of a portion of an exemplary stretchable conductive article 300e having a double slit double beam pattern as shown in FIG. 3C, in a non-planar deformed stretched state. This stretchable conductive article 300e is also of Example 2 described below. Each of a transverse beam 330, an axial beam 320, and a couple multibeams 382 are indicated in the SEM image.

[0110] Referring to FIG. 4, a top view schematic drawing is provided of an exemplary single slit pattern. On the left, the single slit pattern is shown in a planar unstretched state. On the right the single slit pattern is shown in a slightly non-planar deformed stretched state. The single slit pattern includes a plurality of substantially parallel rows 412 of multiple individual linear slits 410. Each of the individual linear slits 410 in a given row 412 is out of phase with each of the individual linear slits 410 in the directly adjacent and substantially parallel row 412. In the specific construction of FIG. 4, the adjacent rows 412 are out of phase by approximately one half of the horizonal spacing. The pattern forms an array of slits 410 and rows 412, and the array has a regular, repeating pattern across the array. Between directly adjacent rows of slits are formed beams 430 of material and between linear slits are formed axial beams 420.

[0111] In some embodiments, the substrate in the planar non-stretched shape has an average thickness of 0.5 micrometers or greater, 1 micrometer, 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 11 micrometers, or 12 micrometers or greater; and 20 micrometers or less, 19 micrometers, 18 micrometers, 17 micrometers, 16 micrometers, 15 micrometers, 14 micrometers, 13 micrometers, 12 micrometers, 11 micrometers, 10 micrometers, 9 micrometers, 8 micrometers, 7 micrometers, 6 micrometers, or 5 micrometers or less. In some cases, the substrate in the planar non-stretched shape has an average thickness between 0.5 micrometers and 20 micrometers.

[0112] Providing a substrate having a thickness in the above range enables production of a stretched article such that when the substrate is in the non-planar deformed stretched shape the article has an average thickness of 5 micrometers or greater, 10 micrometers, 15 micrometers, 25 micrometers, 50 micrometers, 75 micrometers, 100 micrometers, 125 micrometers, 150 micrometers, 175 micrometers, 200 micrometers, 225 micrometers, 250 micrometers, 275 micrometers, 300 micrometers, 325 micrometers, 350 micrometers, 375 micrometers, 400 micrometers, 425 micrometers, 450 micrometers, 475 micrometers, or 500 micrometers or greater; and 800 micrometers or less, 775 micrometers, 750 micrometers, 725 micrometers, 700 micrometers, 675 micrometers, 650 micrometers, 625 micrometers, 600 micrometers, 575 micrometers, 550 micrometers, 525 micrometers, 500 micrometers, 475micrometers, 450 micrometers, 425 micrometers, 400 micrometers, 375 micrometers, 350 micrometers, 325 micrometers, 300 micrometers, 275 micrometers, 250 micrometers, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, or 50 micrometers or less. In some cases, when the substrate is in the non-planar deformed stretched shape the article has an average thickness between 5 micrometers and 800 micrometers.

[0113] There are various features of a Kirigami pattern that may have a size smaller than 500 micrometers. In some embodiments, the at least one feature that is smaller than 500 micrometers comprises one or more of a slit length, an axial beam length, a transverse beam length, a multibeam length, or a distance between two adjacent slits. In certain cases, the feature(s) include a slit length. In certain cases, the feature(s) include an axial beam length. In certain cases, the feature(s) include a transverse beam length. In certain cases, the feature(s) include a multibeam length. In certain cases, the feature(s) include a distance between two adjacent slits.

[0114] In some embodiments of a stretchable conductive article having any of the Kirigami patterns disclosed herein, a portion of the substrate between two adjacent slits has a width of 10 micrometers or greater, 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, 15 micrometers, 15 micrometers, 16 micrometers, 17 micrometers, 18 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 22 micrometers, 23 micrometers, 24 micrometers, or 25 micrometers or greater; and 30 micrometers or less, 29 micrometers, 28 micrometers, 27 micrometers, 26 micrometers, 25 micrometers, 24 micrometers, 23 micrometers, 22 micrometers, 21 micrometers, 20 micrometers, 19 micrometers, 18 micrometers, 17 micrometers, 16 micrometers, or 15 micrometers or less. In certain cases of a stretchable conductive article, a portion of the substrate between two adjacent slits has a width between 10 micrometers and 30 micrometers.

[0115] In some embodiments, each of the plurality of slits independently has a certain average width and a portion of the substrate between two adjacent slits has a certain width. For instance, each of the plurality of slits independently may have an average width of 10 micrometers or greater, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, or 100 micrometers or greater; and 150 micrometers or less, 140 micrometers, 130 micrometers, 120 micrometers, 110 micrometers, 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, 60 micrometers, or 50 micrometers or less. Simultaneously, a portion of the substrate between two adjacent slits has a width of 10 micrometers or greater, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, or 100 micrometers or greater; and 150 micrometers or less, 140 micrometers, 130 micrometers, 120 micrometers, 110 micrometers, 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, 60 micrometers, or 50 micrometers or less. In some cases, each of the plurality of slits independently has an average width between 10 micrometers and 150 micrometers and wherein a portion of the substrate between two adjacent slits has a width between 10 micrometers and 150 micrometers.

[0116] A stretchable conductive article may be formed using various combinations of materials. In some embodiments, the substrate comprises a polymeric film and the article further comprises a metal coatingdeposited on at least a portion of the first major surface of the substrate. For instance, FIG. 5A depicts a generalized schematic side view of a cut polymeric substrate 555 (e.g, polyethylene terephthalate (PET)) in a planar unstretched state, for use in making an exemplary stretchable conductive article. Four sections of polymeric substrate 555 are shown, with a slit 510 inbetween adjacent cut sections 555. FIG. 5B is a generalized schematic side view of the cut polymeric substrate 555 of FIG. 5 A having a first metal coating 540 (e.g., copper) deposited thereon, in a planar unstretched state, and also a generalized schematic side view of the coated substrate in a non-planar deformed stretched state. In the deformed state, instead of seeing slits (510), the article defines large spaces 570 between adjacent sections of coated (540) polymeric substrate 555.

[0117] In certain embodiments, the metal coating is a first metal coating and the article further comprises a second metal coating deposited on at least a portion of the first metal coating opposite the substrate. For examples, FIG. 5C depicts a generalized schematic side view of the coated substrate (e.g., sections of polymeric substrate 555) of FIG. 5B in a planar unstretched state having a second metal coating 545 deposited on the first metal coating 540, and also a generalized schematic side view of the twice-coated substrate in a non-planar deformed stretched state. Again, in the deformed state, instead of seeing slits (510), the article defines large spaces 570 between adjacent sections of coated (540 and 545) polymeric substrate 555. FIG. 5D is a SEM image of a portion of an exemplary stretchable conductive article 500d having two metal coatings (the top coating 545 is indicated in the SEM image) on a polymeric substrate 555. Additionally, an axial beam 520, a transverse beam 530, and two multibeams 582 are indicated in the SEM image.

[0118] FIG. 5E is a photograph of a portion of the exemplary stretchable conductive article 500e of Example 6, having a double slit double beam pattern and a first copper coating deposited on a polymeric substrate, in a planar unstretched state. Next, FIG. 5F is a photograph of a portion of the exemplary stretchable conductive article 500f of Example 6, in a non-planar deformed stretched state. Similarly, FIG. 5G is an SEM image of a portion of the exemplary stretchable conductive article 500g of Example 6, in a non-planar deformed stretched state. An axial beam 520, a transverse beam 530, and two multibeams 582 are indicated in the SEM image.

[0119] FIG. 5H is a photograph of a portion of the exemplary stretchable conductive article 500h of Example 8, having a single slit pattern and a first copper coating deposited on a polymeric substrate, in a planar unstretched state. Next, FIG. 51 is a photograph of a portion of the exemplary stretchable conductive article 500i of Example 8, in a non-planar deformed stretched state. Similarly, FIG. 5 J is an SEM image of a portion of the exemplary stretchable conductive article 500j of Example 8, in a non-planar deformed stretched state. An axial beam 520 and a transverse beam 530 are indicated in the SEM image.

[0120] Exemplary suitable metals for use as a first coating and / or as a second coating to provide electrical conductivity include for instance and without limitation, copper, nickel, tin, gold, and aluminum. In certain cases, each of the first metal coating and the second metal coating independently comprises copper, nickel, tin, gold, or aluminum.

[0121] In some cases, a first metal coating has an average thickness of 50 nanometers (nm) or greater, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 275 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 micrometer, 2 micrometers, 5 micrometers, 10 micrometers, 25 micrometers, 50 micrometers, 75 micrometers, 100 micrometers, 125 micrometers, 150 micrometers, 175 micrometers, 200 micrometers, 225 micrometers, or 250 micrometers or greater; and 500 micrometers or less, 475 micrometers, 450 micrometers, 425 micrometers, 400 micrometers, 375 micrometers, 350 micrometers, 325 micrometers, 300 micrometers, 275 micrometers, 250 micrometers, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, 75 micrometers, 50 micrometers, 25 micrometers, 10 micrometers, 5 micrometers, 2 micrometers, 1 micrometer, 750 nm, 500 nm, 250 nm, or 100 nm or less.

[0122] In some cases, a second metal coating has an average thickness of 50 nanometers (nm) or greater, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 275 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 micrometer, 2 micrometers, 5 micrometers, 10 micrometers, 25 micrometers, 50 micrometers, 75 micrometers, 100 micrometers, 125 micrometers, 150 micrometers, 175 micrometers, 200 micrometers, 225 micrometers, or 250 micrometers or greater; and 500 micrometers or less, 475 micrometers, 450 micrometers, 425 micrometers, 400 micrometers, 375 micrometers, 350 micrometers, 325 micrometers, 300 micrometers, 275 micrometers, 250 micrometers, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, 75 micrometers, 50 micrometers, 25 micrometers, 10 micrometers, 5 micrometers, 2 micrometers, 1 micrometer, 750 nm, 500 nm, 250 nm, or 100 nm or less.

[0123] In select embodiments, each of the first metal coating and the second metal coating independently has an average thickness of between 50 nm and 500 micrometers.

[0124] Exemplary suitable polymeric substrates may be selected from the group consisting of a polypropylene, a polyester, a polyethylene, a polystyrene, a polymethylmethacrylate, a polyamide, a polycarbonate, a polymethyleneoxide, a polybutyleneterephthalate, a styrene acrylonitrile copolymer, a styrene (meth)acrylate copolymer, a styrene maleic anhydride copolymer, a nucleated semi-crystalline polyester, a copolymer of polyethylenenaphthalate, a polyimide copolymer, a polyetherimide, a polyethylene oxides, a copolymer of acrylonitrile, butadiene, and styrene, and blends thereof. In some embodiments, polyethylene terephthalate (PET) is a suitable polyester for use as the polymeric substrate.

[0125] In some embodiments, the substrate comprises a metal fdm to provide electrical conductivity. For instance, a suitable metal film may comprise a metal selected from the group consisting of copper, nickel, aluminum, tin, and gold.

[0126] In some cases in which the substrate includes a metal film, the article further comprises a pressure-sensitive adhesive disposed on at least a portion of the first major surface of the substrate. For instance, FIG. 6A is an SEM image of a portion of an exemplary stretchable conductive article 600a including a metal substrate 655 having a double slit double beam pattern and an adhesive 642 disposed on a major surface of the metal substrate, in a planar unstretched state. In the SEM image, one slit 610 is indicated, as well as an axial beam 620, a transverse beam 630, and two multibeams 682. Thisstretchable conductive article 600a was made according to Example 6 described in detail below. FIG. 6B is an SEM image of a portion of the exemplary stretchable conductive article 600b of FIG. 6A, in a partially non-planar deformed stretched state. An axial beam 620, two multibeams 682, and an adhesive 642 are indicated in the SEM image of FIG. 6B. FIG. 6C is an SEM image of a portion of the exemplary stretchable conductive article 600c of FIG. 6B at a lower magnification. Due to the lower magnification, more of the structure of the partially stretched conductive article 600c is visible. Each of an axial beam 620, a transverse beam 630, three multibeams 682, and two areas of adhesive 642 are indicated in the SEM image of FIG. 6C.

[0127] FIG. 6D is a photograph of a portion of the exemplary stretchable conductive article 600d of Example 6, including a metal substrate and an adhesive disposed on a major surface of the metal substrate, in a non-planar deformed stretched state. Each of an axial beam 620, a transverse beam 630, and two multibeams 682 are indicated in the photograph.

[0128] In some cases in which the substrate includes a metal film, the article further comprises a first layer and a second layer, wherein the substrate is disposed between the first layer and the second layer. For instance, FIG. 7A is a photograph of a portion of the exemplary stretchable conductive article 700a of Example 9, including a metal substrate 755 having a double slit triple beam pattern disposed between two layers, in a planar unstretched state. FIG. 7B is a photograph of a portion of the exemplary stretchable conductive article 700b of FIG. 7A, in a partially non-planar deformed stretched state. In the photograph of FIGS. 7A and 7B, only a first layer 790 is visible. Also indicated are each of an axial beam 720, a transverse beam 730, and three multibeams 782.

[0129] FIG. 7C is a generalized schematic cross-sectional view of an exemplary stretchable conductive article 700c including a cut metal substrate 755 disposed between a first layer 790 and a second layer 792. One slit 710 is also indicated between cut portions of the metal substrate 755 in FIG. 7C.

[0130] In some embodiments including a first layer and a second layer, the first layer comprises an elastomeric polymer film or an adhesive. In some embodiments including a first layer and a second layer, the second layer comprises an elastomeric polymer film or an adhesive. In certain embodiments in which the first layer and the second layer comprise an adhesive, in effect the metal substrate may be embedded in an adhesive (e.g., the first and second layers may be indistinguishable as separate layers).

[0131] Exemplary elastomeric polymer films include for instance and without limitation, a polyurethane, a polyamide, a polyvinyl alcohol, a polyvinyl pyrrolidone, an acrylic, a silicone, a nitrile rubber, a butyl rubber, an ethylene propylene rubber, a chlorosulfonated polyethylene, a polysulfide rubber, an ethylene vinyl acetate (EVA), a co-polyester, a polyether block polyamide copolymer, a polyisobutylene, a polyethylene-propylene rubber, a polyethylene-propylene diene -modified rubber, a polyisoprene, a styrene-isoprene-styrene, a styrene-butadiene-styrene, a styrene-ethylene-propylene-styrene, and a styrene-ethylene-butylene-styrene.

[0132] Exemplary suitable adhesives include for instance and without limitation, pressure-sensitive adhesives and / or hot melt adhesives, e.g., polyurethane adhesives, (methjacrylic adhesives, silicone-basedadhesives, epoxy adhesives, phenolic adhesives, polyvinyl acetate adhesives, polyvinyl alcohol adhesives, polyimide adhesives, and rubber-based adhesives.

[0133] Referring to FIG. 8A, a photograph is provided of a portion of a proof of concept stretchable conductive article 800a including a metal substrate 855 embedded in an adhesive 842, in a non-planar deformed stretched state. The metal substrate 855 is copper having a thickness of 10-50 micrometers and acrylic adhesive 842 was used to form a stretchable conductive article having a total thickness of 600 micrometers. This stretchable conductive article 800a was made according to Example 4 described in detail below.

[0134] FIG. 8B is a photograph of an exemplary stretchable conductive article 800b including a metal substrate 855 embedded in an adhesive 842, in a non-planar deformed stretched state. In this case, the metal substrate 855 is copper having a thickness of 6 micrometers and acrylic adhesive 842 was used to form a stretchable conductive article having a total thickness of 50 micrometers. This stretchable conductive article 800b was made according to Example 5 described in detail below. As such, a metal substrate embedded in an adhesive may be present in either the planar unstretched state or the non-planar deformed stretched state. The non-planar deformed stretched state also encompasses a partially stretched state.

[0135] Methods of Making a Stretchable Conductive Article

[0136] In a second aspect, a method of making a stretchable conductive article is provided. The method comprises:

[0137] forming a plurality of slits in a substrate using a microstructured cutting tool, thereby forming a substrate configured to have a planar unstretched state and a non-planar deformed stretched state, wherein when the substrate is in the planar unstretched state the substrate comprises:

[0138] a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface, the plurality of slits being arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers, and wherein the article is electrically conductive.

[0139] A microstructured cutting tool is a tool including a plurality of microstructures, where each microstructure includes at least one cutting edge. The tool is used to form in the substrate a pattern of cut edges faithfully corresponding to the pattern of the cutting edges of the tool, including cuts that define slits in the substrate having at least one dimension in a plane of the polymeric substrate in a range of about 0.1 micrometers to about 2000 micrometers. Such tools can be made using conventional micromachining processes. Cutting tools for micromachining and methods of making such cutting tools are described in U.S. Pat. Nos.7, 140,812 (Bryan et al.) and 8,443,704 (Burke et al.), for example. Microcutting generally produces sharp cut edges that have a width (e.g., corresponding to the tip width Wt schematically illustrated in FIG.19 of PCT Application Publication No. WO 2022 / 243772 (Johnston et al.)) substantially less (e.g., at least a factor of 2, or at least a factor of 4, or at least a factor of 8 less) than a smallest lateral dimension (e.g., the width W1 schematically illustrated inFIG.19 of WO 2022 / 243772(Johnston et al.)) of the elements formed by micro-cutting. Advantageously, by using a microstructured cutting tool, the edges of the formed slits do not get chemically modified, unlike the edges of slits in substrates that are cut using lasers or ion beams. In certain embodiments, the microstructured cutting tool is a microstructured rotary cutting tool. In some embodiments, the stretchable conductive article is formed using roll-to-roll processing. Two suitable apparatuses for roll-to-roll processing are depicted in FIGS. 9 and 10.

[0140] FIG. 9 is a generalized schematic side view of an apparatus 9000 for use in making an exemplary stretchable conductive article. The apparatus 9000 includes at least a nip roll 9100 having an exterior surface 9110, a patterned roll 9200 including an exterior surface 9210 on which are formed cutting blades 9215 that will cut a Kirigami pattern into a polymeric substrate, and a strip off roll 9300 having an exterior surface 9310. The patterned roll 9200 with cutting blades 9215 may be referred to as a microstructured cutting tool or more specifically as a microstructured rotary cutting tool. This apparatus 9000 further includes a die 9400 configured to coextrude a polymeric substrate material 9500 and a backing material 9600. After coextrusion, the polymeric substrate material 9500 and a backing material 9600 get fed through the exterior surface 9110 of the nip roll 9000 and exterior surface 9210 of the patterned roll 9200, where rotation of the patterned roll 9200 cuts slits having a Kirigami pattern into polymeric substrate material 9500. The polymeric substrate material 9500 and a backing material 9600 solidify before and / or during the cutting step. The resulting cut polymeric substrate 9550 on a backing layer 9650 is then passed over the exterior surface 9310 of the strip off roll 9300 and the polymeric substrate 9550 having a Kirigami pattern 9555 is optionally separated from the backing layer 9650 at that time, forming a cut polymeric substrate 9550.

[0141] FIG. 10 is a generalized schematic side view of another apparatus 10000 for use in making an exemplary stretchable conductive article. The apparatus 10000 includes at least a nip roll 10100 having an exterior surface 10110 and a patterned roll 10200 including an exterior surface 10210 on which are formed cutting blades 10215 that will cut a Kirigami pattern into a polymeric or metal substrate. The patterned roll 10200 with cutting blades 10215 may be referred to as a microstructured cutting tool or more specifically as a microstructured rotary cutting tool. Instead of a die, one of a polymeric or metal substrate 10520 and a backing layer 10620 get fed through the exterior surface 10110 of the nip roll 10100 and exterior surface 10210 of the patterned roll 10200, where rotation of the patterned roll 10200 cuts slits having a Kirigami pattern into the substrate 10520. The resulting cut substrate 10550 having a Kirigami pattern 10555, on the backing layer 10620, is then passed over the exterior surface 10310 of the strip off roll 10300 and the polymeric substrate 10550 is optionally separated from the backing layer 10650 at that time, forming a cut substrate 10550. Further optionally, the stretchable conductive article may be wound into an article roll 10557 for storage and / or transportation prior to use.

[0142] As exemplified in the two general apparatuses of FIGS. 9 and 10, in some cases of roll-to-roll processing, a layer is disposed adjacent to the substrate opposite the microstructured cutting tool during the forming of the plurality of slits, e.g., between a nip roll and the substrate. In some cases, such a layer is an extruded backing and optionally a polymeric substrate is formed by coextruding a polymericresin with the backing and forming the plurality of slits in the polymeric substrate while the polymeric substrate is on the backing. Often, the backing is removed from the cut substrate, although the stretchable conductive article may be stored / transported before final use while still attached to another layer (e.g., a backing layer). The layer is not restricted to the example of a backing layer, but optionally the layer is selected from the group consisting of a backing, a carrier, and a liner. Some suitable backings, carriers, and liner are described below.

[0143] Backings

[0144] Suitable backing layers may broadly include an organic polymeric film, a metal coated film, a metallic foil, a paper, a foam, or a (e.g., woven or non-woven) fibrous web. In some embodiments, the substrate is a woven (including knitted) or (e.g., spunbond or melt blown) nonwoven fibrous web. In certain embodiments, the backing layer comprises a cyclic olefin polymer, a polycarbonate, a polyethylene terephthalate, or a polyethylene terephthalate coated with an acrylic layer.

[0145] Carriers

[0146] Exemplary materials useful as the carrier include, but are not limited to, polyolefins such as polyethylene, polypropylene (including isotactic polypropylene and high impact polypropylene), polystyrene, polyester, including polyethylene terephthalate), polyvinyl chloride, poly(butylene terephthalate), poly(caprolactam), polyvinyl alcohol, polyurethane, poly(vinylidene fluoride), cellulose and cellulose derivatives, such as cellulose acetate and cellophane, and wovens and nonwovens.Commercially available carrier film include kraft paper (available from Monadnock Paper, Inc.); spun-bond poly(ethylene) and poly(propylene), such as those available under the trade designations “TYVEK” and “TYPAR” (available from The Chemours Co.); and porous films obtained from poly(ethylene) and poly(propylene), such as those available under the trade designations “TESLIN” (available from PPG Industries, Inc.), and “CELLGUARD” (available from Hoechst-Celanese).

[0147] Liners

[0148] Suitable (e.g., release) liners may comprise flexible paper and polymeric films having sufficient dimensional stability to hold layers formed thereon in position without excessive stretching. Suitable paper liners include, but are not limited to, densified Kraft paper (commercially available from, for example, Loparex North America, Willowbrook, IL), poly -coated paper such as polyethylene coated Kraft paper, and the like. Suitable polymeric film / liners include, but are not limited to, thermoplastic polymer films including polyalkylenes, e.g., polyethylene and polypropylene; polybutadiene, polyisoprene; polyalkylene oxides, e.g., polyethylene oxide; polyesters, e.g., PET andPBT; polyamides; polycarbonates, polystyrenes, block copolymers of any of the proceeding polymers, and combinations thereof. Other suitable polymeric materials include polyimide, polysilicone, polytetrafluoroethylene, polyethylenephthalate, polyvinylchloride, or combinations thereof. Polymer blends of any of the above may also be employed, and nonwoven or woven liners may also be used.

[0149] In some embodiments, any or all of the major surfaces of a release liner may include a release coating, which may be the same or different, to tune or otherwise modify their release values. In various embodiments, which are not intended to be limiting, the release coatings applied to the major surfaces ofthe release liners may be selected from a fluorine-containing material, a silicone-containing material, a fluoropolymer, a silicone polymer, or a poly(meth)acrylate ester derived from a monomer including an alkyl (meth)acrylate having an alkyl group with 12 to 30 carbon atoms. In one embodiment, the alkyl group on the alkyl (meth)acrylate can be branched. Illustrative examples of useful fluoropolymers and silicone polymers can be found in U.S. Patent No. 4,472,480 (Olson), U.S. Patent No. 4,567,073 and U.S. Patent No. 4,614,667 (both Larson et al), incorporated herein by reference in their entireties. Illustrative examples of useful poly(meth)acrylate esters can be found in U.S. Patent Appl. Publ. No. 2005 / 0118352 (Suwa), incorporated herein by reference in its entirety.

[0150] Referring now to FIG. 11, a generalized schematic side view is provided of an additional apparatus 11000 for use in making an exemplary stretchable conductive article. Such an apparatus 11000 may be used when the substrate comprises a metal film. For instance, a method that forms slits in a Kirigami pattern in a metal film may further include stretching the substrate into the non-planar deformed stretched state and depositing a pressure-sensitive adhesive on the substrate. As depicted in FIG. 11, a stretched substrate 11550 is placed on a layer 11900 and a polymerizable composition (e.g., a pressuresensitive adhesive prepolymer) 11841 is deposited on the stretched substrate 11550. In this case, a second layer 11902 is brought into contact with the adhesive-coated stretched substrate 11550 and the full construction is passed between a first nip roller 11100 and a second nip roller 11101 to press the polymerizable composition 11841 into the stretched substrate 11550. Next, the construction is exposed to actinic radiation and / or heat to polymerize the polymerizable composition 11841. Optionally, a first source 11700 and a second source 11701 of actinic radiation and / or heat are provided on opposing sides of the construction. In some cases, UV radiation is a suitable form of actinic radiation, particularly when the polymerizable composition includes a UV photoinitiator. With the polymerization, a stretchable conductive article 1100 is formed.

[0151] In some methods in which the substrate is a metal film, the method further includes disposing the substrate between a first layer and a second layer. Suitable materials for the first and second layers, e.g., one or more elastomeric polymer film(s) or adhesive(s), are described in detail above with respect to the first aspect. In select embodiments, the method includes embedding the metal substrate in an adhesive, for instance as done in preparing the articles shown in FIGS. 8A-8B. In some cases, a laminate may be formed by placing the metal substrate on the first layer and then placing the second layer on the substrate opposite the first layer. Various means for positioning a metal substrate between two layers may be used to form such a stretchable conductive article.

[0152] FIG. 12 provides a generalized schematic side view of a further apparatus 12000 for use in making an exemplary stretchable conductive article. In this apparatus 12000, the substrate 12520 comprises a polymeric film that unwinds from a substrate roller 12521. Optionally, the apparatus includes a liner 12900 on which the substrate 12520 travels throughout the process of forming a stretchable conducting article, for instance a liner 12900 that unwinds from a liner roller 12300. The substrate 12520 has a Kirigami pattern of slits cut through the substrate 12520 using a microstructured cutting tool 12200 that has a plurality of cutting blades 12215 formed on an exterior surface 12210 of themicrostructured cutting tool 12200, thereby forming a cut substrate 12550. The method further includes depositing a metal coating 12540 on at least a portion of the first major surface 12523 of the substrate. Any well-known vacuum deposition method can be employed, such as, for example, a sputter deposition method, an evaporation method, an ion plating method, a physical vapor deposition method, or a chemical vapor deposition method. As shown in FIG. 12, in some cases, the metal coating 12540 is deposited when the (e.g., cut) substrate 12550 is in the planar unstretched state. In alternate embodiments, however, the metal coating 12540 may instead be deposited when the (e.g., cut) substrate 12550 is in the non-planar deformed stretched state.

[0153] Optionally, the metal coating 12540 is a first metal coating and the method further comprises electroplating a second metal coating 12545 on at least a portion of the first metal coating 12540 opposite the substrate 12550. Exemplary suitable electroplating equipment may be obtained from Technic, for instance a MP200CS roll-to-roll wet processing system. U.S. Patent No. 6,991,717 (King et al.) also describes a suitable horizontal processing equipment that may be used in an electrodeposition process. It was discovered that while the deposition of too much metal via vacuum deposition can undesirably weld the slits in the substrate together, surprisingly, instead of welding slits together electroplating growth continued underneath the cut substrate towards the substrate’s underside, which is advantageous for Z-axis conductivity. For instance, referring back to FIG. 5C, a few areas 547 of the second metal coating 545 are depicted as being located on the underside of the cut substrate 555.

[0154] In the embodiment of FIG. 12, the liner 12900 is optionally rewound onto a second liner roll 12301, which separates the stretchable conductive article 1200 from the liner 12900. As shown in FIG.12, the stretchable conductive article 1200 gets stretched from a planar unstretched state to a non-planar deformed stretched state after separation from the liner 12900. Also as depicted in FIG. 12, optionally, the stretchable conductive article 1200 may be passed between a first nip roller 12100 and a second nip roller 12101 to compress the stretchable conductive article 1200 to a desired thickness. Further optionally, the stretchable conductive article 1200 may be wound into an article roll 12557 for storage and / or transportation prior to use.

[0155] It is expressly contemplated that the resulting stretchable conductive article made according to such methods of the second aspect may be according to any embodiment of the first aspect described in detail above.

[0156] Select Embodiments of the Disclosure

[0157] In a first embodiment, the present disclosure provides a stretchable conductive article. The stretchable conductive article comprises a substrate configured to have a planar unstretched state and a non-planar deformed stretched state. When the substrate is in the planar unstretched state the substrate comprises a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface. The plurality of slits is arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers. The article is electrically conductive.

[0158] In a second embodiment, the present disclosure provides a stretchable conductive article according to the first embodiment, wherein the substrate comprises a polymeric film and the article further comprises a metal coating deposited on at least a portion of the first major surface of the substrate.

[0159] In a third embodiment, the present disclosure provides a stretchable conductive article according to the second embodiment, wherein the metal coating is a first metal coating and the article further comprises a second metal coating deposited on at least a portion of the first metal coating opposite the substrate.

[0160] In a fourth embodiment, the present disclosure provides a stretchable conductive article according to the second embodiment or the third embodiment, wherein each of the first metal coating and the second metal coating independently has an average thickness of between 50 nanometers (nm) and 500 micrometers.

[0161] In a fifth embodiment, the present disclosure provides a stretchable conductive article according to any of the second through fourth embodiments, wherein each of the first metal coating and the second metal coating independently comprises copper, nickel, tin, gold, or aluminum.

[0162] In a sixth embodiment, the present disclosure provides a stretchable conductive article according to any of the second through fifth embodiments, wherein the polymeric film is selected from the group consisting of a polypropylene, a polyester, a polyethylene, a polystyrene, a polymethylmethacrylate, a polyamide, a polycarbonate, a polymethyleneoxide, a polybutyleneterephthalate, a styrene acrylonitrile copolymer, a styrene (methjacrylate copolymer, a styrene maleic anhydride copolymer, a nucleated semicrystalline polyester, a copolymer of polyethylenenaphthalate, a polyimide copolymer, a polyetherimide, a polyethylene oxides, a copolymer of acrylonitrile, butadiene, and styrene, and blends thereof.

[0163] In a seventh embodiment, the present disclosure provides a stretchable conductive article according to the sixth embodiment, wherein the substrate comprises a metal film.

[0164] In an eighth embodiment, the present disclosure provides a stretchable conductive article according to the first embodiment, wherein the article further comprises a pressure-sensitive adhesive disposed on at least a portion of the first major surface of the substrate.

[0165] In a ninth embodiment, the present disclosure provides a stretchable conductive article according to the seventh embodiment, wherein the article further comprises a first layer and a second layer, wherein the substrate is disposed between the first layer and the second layer.

[0166] In a tenth embodiment, the present disclosure provides a stretchable conductive article according to the ninth embodiment, wherein the first layer comprises an elastomeric polymer film or an adhesive.

[0167] In an eleventh embodiment, the present disclosure provides a stretchable conductive article according to the ninth embodiment or the tenth embodiment, wherein the second layer comprises an elastomeric polymer film or an adhesive.

[0168] In a twelfth embodiment, the present disclosure provides a stretchable conductive article according to the seventh embodiment, wherein the substrate is embedded in an adhesive, wherein the substrate is in either the planar unstretched state or the non-planar deformed stretched state.

[0169] In a thirteenth embodiment, the present disclosure provides a stretchable conductive article according to any of the seventh through twelfth embodiments, wherein the metal fdm comprises a metal selected from the group consisting of copper, nickel, aluminum, tin, and gold.

[0170] In a fourteenth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through thirteenth embodiments, wherein the substrate in the planar nonstretched shape has an average thickness between 0.8 micrometer and 20 micrometers.

[0171] In a fifteenth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through fourteenth embodiments, wherein when the substrate is in the non-planar deformed stretched shape the article has an average thickness between 20 micrometers and 800 micrometers.

[0172] In a sixteenth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through fifteenth embodiments, wherein the at least one feature that is smaller than 500 micrometers comprises one or more of a slit length, an axial beam length, a transverse beam length, a multibeam length, or a distance between two adjacent slits.

[0173] In a seventeenth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through sixteenth embodiments, wherein each of the plurality of slits independently has an average width between 10 micrometers and 150 micrometers and wherein a portion of the substrate between two adjacent slits has a width between 10 micrometers and 150 micrometers.

[0174] In an eighteenth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through seventeenth embodiments, wherein the Kirigami pattern is selected from the group consisting of single unidirectional patterns and multi-slit unidirectional patterns.

[0175] In a nineteenth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through eighteenth embodiments, comprising a portion of the substrate between two adjacent slits having a width between 10 micrometers and 30 micrometers.

[0176] In a twentieth embodiment, the present disclosure provides a stretchable conductive article according to any of the first through nineteenth embodiments, having a form of a roll.

[0177] In a twenty -first embodiment, the present disclosure provides a method of making a stretchable conductive article. The method comprises forming a plurality of slits in a substrate using a microstructured cutting tool, thereby forming a substrate configured to have a planar unstretched state and a non-planar deformed stretched state. When the substrate is in the planar unstretched state the substrate comprises a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface. The plurality of slits is arranged in a Kirigami pattern, which comprises at least one feature that is smaller than500 micrometers. The article is electrically conductive.

[0178] In a twenty-second embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty -first embodiment, wherein the substrate comprises a polymeric film and the method further comprises depositing a metal coating on at least a portion of the first major surface of the substrate.

[0179] In a twenty -third embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty-second embodiment, wherein the depositing comprises vacuum deposition.

[0180] In a twenty -fourth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty-second embodiment or the twenty -third embodiment, wherein the depositing is performed when the substrate is in the planar unstretched state.

[0181] In a twenty -fifth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty-second embodiment or the twenty -third embodiment, wherein the depositing is performed when the substrate is in the non-planar deformed stretched state.

[0182] In a twenty-sixth embodiment, the present disclosure provides a method of making a stretchable conductive article according to any of the twenty -second through twenty -fifth embodiments, wherein the metal coating is a first metal coating and the method further comprises electroplating a second metal coating on at least a portion of the first metal coating opposite the substrate.

[0183] In a twenty-seventh embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty -first embodiment, wherein the substrate comprises a metal film.

[0184] In a twenty-eighth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty-seventh embodiment, further comprising stretching the substrate into the non-planar deformed stretched state and depositing a pressure-sensitive adhesive on the substrate.

[0185] In a twenty -ninth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty-seventh embodiment, further comprising disposing the substrate between a first layer and a second layer.

[0186] In a thirtieth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty -ninth embodiment, wherein each of the first layer and the second layer independently comprises an elastomeric polymer film or an adhesive.

[0187] In a thirty -first embodiment, the present disclosure provides a method of making a stretchable conductive article according to the twenty-seventh embodiment, further comprising embedding the substrate in an adhesive.

[0188] In a thirty-second embodiment, the present disclosure provides a method of making a stretchable conductive article according to any of the twenty -first through thirty -first embodiments, wherein the stretchable conductive article is formed using roll-to-roll processing.

[0189] In a thirty -third embodiment, the present disclosure provides a method of making a stretchable conductive article according to the thirty-second embodiment, wherein a layer is disposed adjacent to the substrate opposite the microstructured cutting tool during the forming of the plurality of slits, wherein the layer is selected from the group consisting of a backing, a carrier, and a liner.

[0190] In a thirty -fourth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the thirty -third embodiment, wherein the layer comprises a cyclic olefinpolymer, a polycarbonate, a polyethylene terephthalate, or a polyethylene terephthalate coated with an acrylic layer.

[0191] In a thirty -fifth embodiment, the present disclosure provides a method of making a stretchable conductive article according to the thirty -third embodiment or the thirty-fourth embodiment, wherein the layer is an extmded backing.

[0192] In a thirty-sixth embodiment, the present disclosure provides a method of making a stretchable conductive article according to any of the twentieth through thirty -fifth embodiments, wherein the microstructured cutting tool is a microstructured rotary cutting tool.

[0193] In a thirty-seventh embodiment, the present disclosure provides a method of making a stretchable conductive article according to any of the twenty -first through thirty-sixth embodiments, wherein the stretchable conductive article is according to any of the first through twentieth embodiments.EXAMPLES

[0194] Unless otherwise noted or readily apparent from the context, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. Table 1 (below) lists materials used in the examples and their sources. In the Tables, "NA" means not applicable. In the examples:TABLE 1. Materials List

[0195] Example 1 - 3 Different Double Slit micro-Kirigami patterns were cut in a 6 micrometers thick and 75 or 150 millimeters wide Copper foil using micro structured rotary cutting tools. The uncut Copper with a 75 micrometers thick COP liner at the back was fed into the tool against a backing roll and force up to 4000 lb was applied to cut the Copper foil. COP was also successfully used as a backing liner for cutting Copper foils. The microstructured rotary tool blades were oriented in the machine direction.1. Double Slit Single Beam (FIGS. IE and IF). The microstructured rotary cutting tool was manufactured to cut a pattern as illustrated in FIG. 1C and designed to cut slits that are 1400 micrometers long, spaced 150 micrometers apart in the transverse direction and 700 micrometers apart in the longitudinal direction. The 150 micrometer spacing of adjacent slits is a feature of the Kirigami pattern that is smaller than 500 micrometers.2. Double Slit Double Beam (FIGS. 3D and 3E). The microstructured rotary cutting tool was manufactured to cut a pattern as illustrated in FIG. 3 A and designed to cut slits that are 1400 micrometers long, spaced 150 micrometers apart in the transverse direction, and 700 micrometers apart in the longitudinal direction. The smaller slit that creates the double beam feature between the bigger slits was 500 micrometers in length and spaced equally at 75 micrometers from the bigger slits. The 150 micrometer spacing of adjacent slits and the 75 micrometer spacing between adjacent multibeam slits are both features of the Kirigami pattern that are smaller than 500 micrometers.3. Double Slit Triple Beam (FIGS. 2F, 2G, and 2H). The microstructured rotary cutting tool was manufactured to cut a pattern as illustrated in FIG. 2C and designed to cut slits that are 1400 micrometers long, and spaced 150 micrometers apart in the transverse direction, and 700 micrometers apart in the longitudinal direction. The two smaller slits that create the triple beam feature between the bigger slits were 500 micrometers in length and spaced equally 50 micrometers apart and from the bigger slits. The 150 micrometer spacing of adjacent slits and the 50 micrometer spacing between adjacent multibeam slits are both features of the Kirigami pattern that are smaller than 500 micrometers.

[0196] Example 4 - An adhesive embedded micro-kirigami copper foil was made as follows: A Kirigami pattern was cut in a 10 to 50 micrometers thick Copper Foil. A prepolymerized syrup was prepared by adding 0.04 pph of photoinitiator (Irgacure 651) into 100 parts by weight of acrylate (IO A) and conducting low intensity radiation polymerization until the temperature was raised by 3~ 10 °C. Acrylic prepolymer syrup was prepared by mixing prepolymerized syrup: IOA (92 pph), AA (8 pph), Irgacure 651 (0.2 pph), and HDDA (0.2 pph). Acrylic prepolymer syrup was coated between 50 micrometer thick polyethylene terephthalate support films release treated with fluoro silicate by using dual rollers and a stretched micro-kirigami copper foil was embedded into the acrylic syrup. Total energy density was controlled between 1000 mJ / cm2and 3000 mJ / cm2. The spacing between rollers was adjusted to achieve the 600 micrometers thickness. (FIG. 8A)

[0197] Example 5 - An adhesive embedded micro-kirigami copper foil was made as follows: Double Slit Double beam micro-Kirigami pattern was cut in a 6 micrometers thick and 75 millimeters wide Copper Foil as described in the Example 2 above. A prepolymerized syrup was prepared by adding 0.04 pph of photoinitiator (Irgacure 651) into 100 parts by weight of acrylate (IO A) and conducting low intensity radiation polymerization until the temperature was raised by 3~ 10 °C. Acrylic prepolymer symp was prepared by mixing prepolymerized syrup: IOA (92 pph), AA (8 pph), Irgacure 651 (0.2 pph), and HDDA (0.2 pph). Acrylic prepolymer syrup was coated between 50 micrometer thick polyethylene terephthalate support films release treated with fluorosilicate by using dual rollers and stretched micro-kirigami copper foil was embedded into the acrylic syrup. Total energy density was controlled between 1000 mJ / cm2and 3000 mJ / cm2. The spacing between rollers was adjusted to achieve the 50 micrometers thickness. (FIG. 8B)

[0198] Example 6 - Double Slit Double Beam micro-Kirigami pattern was cut in a 4.5 micrometer thick and 200 mm wide PET film using the microstructured rotary cutting tool. The uncut PET film, with a 75 micrometers thick NSNF polymeric liner at the back, was fed into the tool against a backing roll and force up to 4000 lb was applied to cut the PET film. The rotary tool blades were oriented in the machine direction. The pattern dimensions were the same as described above in Example 2. The cut fdm was metallized on one side using vacuum sputtering from a copper target to create a 200 nanometer thick seed Copper layer followed by electroplating to create a 1-2 micrometer thick Copper layer.

[0199] Procedure for electroplating of metal layers: Substrates containing the kirigami vacuum coated conductor lines were trimmed such that they fit into the copper plating bath. A stripe of silver conductive paint (~ !4 cm) was applied along the outer perimeter of the trimmed substrate such that the paint physically contacted the conductor lines and provided electrical contact between the conductors and the power supply. The conductive paint was allowed to dry according to manufacturer’s instructions. Strips of 3M 1280 circuit plating tape were applied along the edges of each substrate sample to seal the ends of the exposed conductors, as well as to cover the silver paint. A comer of each painted sample was left uncovered by the plating tape such that an alligator clip could be used to make electrical contact between the substrate and a DC power supply. A standard acid-based copper plating bath was used to deposit copper onto the conductive lines. A current density of 18A / ft2was used to plate copper onto the conductive lines, and the duration of the plating was adjusted accordingly to meet specific copper deposit thickness. A consumable copper anode was used for electroplating. After electroplating, each sample was rinsed with DI water, and dried with compressed air.

[0200] Example 7- Double Slit Double Beam micro-Kirigami pattern was cut in a 4.5 micrometer thick and 200 mm wide PET film using the microstructured rotary cutting tool. The uncut PET film, with a 75 micrometers thick NSNF polymeric liner at the back, was fed into the tool against a backing roll and force up to 4000 lb was applied to cut the PET film. The rotary tool blades were oriented in the machinedirection. The pattern dimensions were the same as described above in Example 2. The cut film is metallized on one side using vacuum sputtering to create a 200 nanometer thick Copper layer. This was followed by electroplating (detailed above) a second layer of Nickel a few microns in thickness atop the first Copper layer. (FIG. 5D)

[0201] Example 8 - A Single Slit micro-Kirigami pattern was cut in 4.5 micrometers thick and 150 mm wide PET film using the microstmctured rotary cutting tool. The uncut PET film with a 75 micrometers thick NSNF polymeric liner at the back was fed into the tool against a backing roll and force up to 4000 lb was applied to cut the PET film. The microstructured rotary tool blades were oriented in the machine direction. The microstructured rotary cutting tool was manufactured to cut a pattern with slits that are ~250 micrometers long and spaced 50 micrometers apart in the longitudinal (along the slits) direction with a spacing of 38 micrometers between adjacent rows. The slit length of 250 micrometers, distance between adjacent slits of 50 micrometers, and distance between adjacent rows of 38 micrometers are all features of the Kirigami pattern that are smaller than 500 micrometers. The cut film was metallized on one side using vacuum sputtering to create a 200 nanometer thick Copper layer followed by electroplating (detailed above) to add an additional 200 nanometer thick Copper layer.

[0202] Example 9 - A Double Slit Double beam micro-Kirigami pattern was cut in a 6 micrometers thick and 75 millimeters wide Copper Foil as described in the Example 2 above. The unstretched planar kirigami foil was disposed between two layers of 3M™ Tegaderm™ transparent film dressing to create the stretchable conductor. (FIGS. 7A and 7B)

[0203] Example 10 - A Single Slit micro-Kirigami pattern was cut in 25 micrometers thick and 125 millimeters wide TORAYFAN PMX2 Aluminum coated polypropylene film using the microstructured rotary cutting tool. The uncut film, with a 75 micrometers thick PET liner at the back, was fed into the tool against a backing roll and force up to 4000 lb was applied to cut the film. The micro structured rotary tool blades were oriented in the machine direction. The microstructured rotary cutting tool was manufactured to cut a pattern with slits that are ~575 micrometers long and spaced 125 micrometers apart in the longitudinal (e.g., along the slits) direction with a spacing of 125 micrometers between adjacent rows. The 125 micrometer longitudinal spacing of adjacent slits and the 125 micrometer spacing between adjacent slits are both features of the Kirigami pattern that are smaller than 500 micrometers. FIG. 13 A is a photograph of a roll of the stretchable conductive article 1300a in an unstretched state. As can be seen in the figure, a portion 1303 of the aluminum coated polypropylene film 1310 includes the Kirigami pattern whereas two portions 1301 and 1305 of the aluminum coated polypropylene film 1310 located on either side of the portion 1303 remain uncut. FIG. 13B provides a close up view of a portion of the stretchable conductive article 1300b of Example 10, unrolled, and in a non-planar deformed stretched state.

[0204] Other modifications and variations to the present disclosure may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present disclosure, which is more particularly set forth in the appended claims. It is understood that aspects of the various embodiments may be interchanged in whole or part or combined with other aspects of the various embodiments. All cited references, patents, or patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

What is claimed is:

1. A stretchable conductive article comprising a substrate configured to have a planar unstretched state and a non-planar deformed stretched state, wherein when the substrate is in the planar unstretched state the substrate comprises:a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the second major surface, the plurality of slits being arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers, andwherein the article is electrically conductive.

2. The stretchable conductive article of claim 1, wherein the substrate comprises a polymeric film and the article further comprises a metal coating deposited on at least a portion of the first major surface of the substrate.

3. The stretchable conductive article of claim 2, wherein the metal coating is a first metal coating and the article further comprises a second metal coating deposited on at least a portion of the first metal coating opposite the substrate.

4. The stretchable conductive article of claim 2 or claim 3, wherein each of the first metal coating and the second metal coating independently has an average thickness of between 50 nanometers (nm) and 500 micrometers.

5. The stretchable conductive article of any of claims 2 to 4, wherein each of the first metal coating and the second metal coating independently comprises copper, nickel, tin, gold, or aluminum.

6. The stretchable conductive article of any of claims 2 to 5, wherein the polymeric film is selected from the group consisting of a polypropylene, a polyester, a polyethylene, a polystyrene, a polymethylmethacrylate, a polyamide, a polycarbonate, a polymethyleneoxide, a polybutyleneterephthalate, a styrene acrylonitrile copolymer, a styrene (meth)acrylate copolymer, a styrene maleic anhydride copolymer, a nucleated semi-crystalline polyester, a copolymer of polyethylenenaphthalate, a polyimide copolymer, a polyetherimide, a polyethylene oxides, a copolymer of acrylonitrile, butadiene, and styrene, and blends thereof.

7. The stretchable conductive article of claim 1, wherein the substrate comprises a metal film.

8. The stretchable conductive article of claim 7, wherein the article further comprises a pressuresensitive adhesive disposed on at least a portion of the first major surface of the substrate.

9. The stretchable conductive article of claim 7, wherein the article further comprises a first layer and a second layer, wherein the substrate is disposed between the first layer and the second layer.

10. The stretchable conductive article of claim 9, wherein the first layer comprises an elastomeric polymer film or an adhesive.

11. The stretchable conductive article of claim 9 or claim 10, wherein the second layer comprises an elastomeric polymer film or an adhesive.

12. The stretchable conductive article of claim 7, wherein the substrate is embedded in an adhesive, wherein the substrate is in either the planar unstretched state or the non-planar deformed stretched state.

13. The stretchable conductive article of any of claims 7 to 12, wherein the metal film comprises a metal selected from the group consisting of copper, nickel, aluminum, tin, and gold.

14. The stretchable conductive article of any of claims 1 to 13, wherein the substrate in the planar non-stretched shape has an average thickness between 0.8 micrometer and 20 micrometers.

15. The stretchable conductive article of any of claims 1 to 14, wherein when the substrate is in the non-planar deformed stretched shape the article has an average thickness between 20 micrometers and 800 micrometers.

16. The stretchable conductive article of any of claims 1 to 15, wherein the at least one feature that is smaller than 500 micrometers comprises one or more of a slit length, an axial beam length, a transverse beam length, a multibeam length, or a distance between two adjacent slits.

17. The stretchable conductive article of any of claims 1 to 16, wherein each of the plurality of slits independently has an average width between 10 micrometers and 150 micrometers and wherein a portion of the substrate between two adjacent slits has a width between 10 micrometers and 150 micrometers.

18. The stretchable conductive article of any of claims 1 to 17, wherein the Kirigami pattern is selected from the group consisting of single unidirectional patterns and multi-slit unidirectional patterns.

19. The stretchable conductive article of any of claims 1 to 18, comprising a portion of the substrate between two adjacent slits having a width between 10 micrometers and 30 micrometers.

20. The stretchable conductive article of any of claims 1 to 19, having a form of a roll.

21. A method of making a stretchable conductive article, the method comprising:forming a plurality of slits in a substrate using a microstructured cutting tool, thereby forming a substrate configured to have a planar unstretched state and a non-planar deformed stretched state, wherein when the substrate is in the planar unstretched state the substrate comprises:a sheet comprising a first major surface; a second major surface opposite the first major surface; and a plurality of slits that each extend from the first major surface to the secondmajor surface, the plurality of slits being arranged in a Kirigami pattern, which comprises at least one feature that is smaller than 500 micrometers, andwherein the article is electrically conductive.

22. The method of claim 21, wherein the substrate comprises a polymeric film and the method further comprises depositing a metal coating on at least a portion of the first major surface of the substrate.

23. The method of claim 22, wherein the depositing comprises vacuum deposition.

24. The method of claim 22 or claim 23, wherein the depositing is performed when the substrate is in the planar unstretched state.

25. The method of claim 22 or claim 23, wherein the depositing is performed when the substrate is in the non-planar deformed stretched state.

26. The method of any of claims 22 to 25, wherein the metal coating is a first metal coating and the method further comprises electroplating a second metal coating on at least a portion of the first metal coating opposite the substrate.

27. The method of claim 21, wherein the substrate comprises a metal film.

28. The method of claim 27, further comprising stretching the substrate into the non-planar deformed stretched state and depositing a pressure-sensitive adhesive on the substrate.

29. The method of claim 27, further comprising disposing the substrate between a first layer and a second layer.

30. The method of claim 29, wherein each of the first layer and the second layer independently comprises an elastomeric polymer film or an adhesive.

31. The method of claim 27, further comprising embedding the substrate in an adhesive.

32. The method of any of claims 21 to 31, wherein the stretchable conductive article is formed using roll-to-roll processing.

33. The method of claim 32, wherein a layer is disposed adjacent to the substrate opposite the microstructured cutting tool during the forming of the plurality of slits, wherein the layer is selected from the group consisting of a backing, a carrier, and a liner.

34. The method of claim 33, wherein the layer comprises a cyclic olefin polymer, a polycarbonate, a polyethylene terephthalate, or a polyethylene terephthalate coated with an acrylic layer.

35. The method of claim 33 or claim 34, wherein the layer is an extruded backing.

36. The method of any of claims 21 to 35, wherein the microstructured cutting tool is a microstructured rotary cutting tool.

37. The method of any of claims 21 to 36, wherein the stretchable conductive article is of any of claims 1 to 20.

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