Material and method of manufacture

Abstract

A shape memory alloy (SMA) wire 102 is knitting (or sewn, stitched) through a substrate 101 to create a smart material whose shape or stiffness can be controlled by heating the SMA wires e.g. electrically. The substrate may comprise holes formed by tubes 104. The tubes 104 may be arranged in rows, and the direction of tubes in adjacent rows may be offset from each other. Also claimed is a method and kit of parts for creating the material.

Description

Technical Field The present disclosure relates to a material and method of manufacture, and particularly, but not exclusively, a composite smart material and method of manufacture. Background Smart materials are materials that are able to change their properties, such as shape or elasticity, due to an external stimulus, such as heat, light, pressure or electricity. Such smart materials can be used as actuators which are helpful in soft robotics and flexible mechanical systems. Such materials have been proposed for use in medical devices taking advantage of stress-induced transformation for self-expanding implantable devices, such as endovascular stents and vena cava filters. Further development of new smart materials appropriate for other settings will bring further benefits to many areas of technology. Summary There is provided a method of manufacture of a material, the method comprising: providing a substrate, providing a shape memory alloy wire (SMA wire), and knitting the shape memory alloy wire through the substrate. In this application, knitting the SMA wire into a substrate comprises passing the wire through the substrate in a pattern. Once knitted in the substrate, the SMA wire is embedded in the substrate such that the SMA wire passes through the substrate in the pattern. The use of the substrate allows the resulting material to be much stronger than a material made only of one or more shape memory alloy wires. The material is a smart material due to the embedded SMA wire. Optionally, the substrate has holes therethrough and knitting the SMA wire through the substrate comprises passing the SMA wire through a subset of the holes, and, optionally, all of the holes. Optionally, the holes are formed by tubes through the substrate and / or the holes / tubes are arranged in rows, the SMA wire being passable through the holes / tubes. The tubes may be arranged so that the direction though tubes in adjacent rows are offset from one another. For example, directions of tubes in adjacent rows may be offset by 45 to 90 degrees. Tubes in every second row may have a common direction and tubes in the intervening rows may have a common direction to each other. The directions of the tubes may be diagonal to a face of the substrate. The tubes may have a round cross-section, such as a circular cross section. Optionally, the tubes have a diameter, or width, of between 0.2 and 1cm and / or a wall thickness of between 0.05 and 0.3cm and / or a distance between tube centres of between 0.3 and 1.5cm. Further reinforcement of the connections between tubes may be given by rods of diameter between 0.05 and 0.3cm attached between the tubes. Alternatively, the process of knitting the SMA wire into the substrate can form the holes in the substrate, for example, using a needle or the SMA wire to pierce a hole into the substrate, through which the SMA wire can pass. Optionally, the method further comprises forming the substrate, for example, using 3D printing. Optionally, forming the substrate comprises 3D printing the substrate in a soluble PVA negative mould. Optionally, the substrate is formed by injecting liquid silicone rubber into the mould, optionally with a shore of A30, A20 and / or A12. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a row, wherein a back and forth pattern comprises the shape memory alloy wire being passed through a first tube in a row, then through an adjacent tube in the row in the opposite direction, and repeating this pattern. The pattern may be repeated throughout a subset, and optionally all of, the rows in the substrate. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction and then in a back and forth pattern along a second row in a second direction, opposite the first direction. Optionally, this pattern may be repeated through all rows of the substrate. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction from a first edge of the substrate to a mid-point of the substrate and then in a back and forth pattern along a second row in a second direction, opposite the first direction from the mid-point of the substrate to the first edge, and a second shape memory alloy wire is knitted in a back and forth pattern along the first row in the second direction from a second edge, opposite the first edge of the substrate, to the mid-point of the substrate and then in a back and forth pattern along the second row in the first direction, from the mid-point of the substrate to the second edge. Optionally, the second row is adjacent the first row. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction from a mid-point of the substrate to a first edge of the substrate, and a second shape memory alloy wire is knitted in a back and forth pattern along a second row in a second direction, opposite the first direction from the mid-point to a second edge opposite the first edge of the substrate. Optionally, the second row is adjacent the first row. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction from a first edge of the substrate to a mid-point of the substrate and then in a back and forth pattern along a second row in the first direction, from the midpoint of the substrate to a second edge, opposite the first edge, and a second shape memory alloy wire is knitted in a back and forth pattern along the first row in a second direction, opposite the first direction from the second edge to the mid-point of the substrate and then in a back and forth pattern along the first row in the second direction, from the mid-point of the substrate to the first edge. Optionally, the second row is adjacent the first row. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction from a mid-point of the substrate to a second edge and then in a back and forth pattern along a second row in a second direction, opposite the first direction from the second edge of the substrate to the mid-point, and the same shape memory alloy wire is knitted in a back and forth pattern along the second row in the second direction from the mid-point of the substrate, the first edge of the substrate and then in a back and forth pattern along the first row in the first direction, from the first edge of the substrate to the mid-point. Optionally, the second row is adjacent the first row. Optionally, the substrate is compressible. Optionally, the substrate is elastic. Optionally, the substrate is a silicone substrate. Optionally, the shape memory alloy wire is nickel-titanium shape memory alloy wire, for example, a Flexinol® shape memory alloy wire. Optionally, the shape memory alloy wire is temperature actuated, for example, the shape memory alloy wire may have an actuation temperature of 90C, 50C or 40C at which, the SMA wire changes shape. Optionally, the substrate has a melting temperature higher than an activation temperature of the SMA wire. This is advantageous as the SMA wire may be actuated without damaging the substrate. Optionally, the actuation temperature of the shape memory alloy wire is less than 50C or 40C. An actuation temperature of less than 40C may allow body temperature to be used to actuate the SMA wire. Optionally, the actuation temperature of the shape memory alloy wire is more than 30C. Optionally, the shape memory alloy wire is voltage actuated. Optionally, the SMA wire may be indirectly voltage actuated, for example, the application of voltage to the SMA wire may increase the temperature of the SMA wire to reach the SMA wire actuation temperature. For example, a voltage of 3V or 5V may be applied to the SMA wire to heat the SMA wire and thereby actuate the SMA wire. Optionally, the method may further comprise connecting a chip to the SMA wire, the chip configured to control voltage applied to the wire. In this way, the chip can determine when to activate the SMA wire and provide and / or adjust the required voltage accordingly. The chip may change the voltage dependent on time, measured pressure, temperature or other sensed parameters. There is further provided a method of manufacture of a composite material, wherein the composite material has a plurality of zones and in each zone a method according to the method described above is performed, wherein in each zone, the shape memory alloy wire is knitted in a different pattern and / or the substrate is formed of a different material and / or a different shape memory alloy wire is used. The formation of a composite material can enable a network of compression to be formed in the substrate. Use of modelling can enable the design of a bespoke compression pattern across the composite material for use in the required application. There is further provided a material, the material comprising: a substrate, and a shape memory alloy wire, wherein the shape memory alloy wire is knitted through the substrate. Optionally, the substrate has holes therethrough and the SMA wire passes through a subset of the holes. Optionally, the holes are formed by tubes arranged in rows, the wire passing through the tubes. The tubes may be arranged so that the direction though tubes in adjacent rows are offset from one another. For example, directions of tubes in adjacent rows may be offset by 45 to 90 degrees. Tubes in every second row may have a common direction and tubes in the intervening rows may have a common direction to each other. The directions of the tubes may be diagonal to a face of the substrate. Optionally, the tubes have a diameter of between 0.2 and 1cm and a thickness of between 0.05 and 0.3cm and a distance between tube centres of between 0.3 and 1.5cm. Further reinforcement of the connections between tubes may be given by rods of diameter between 0.05 and 0.3cm. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a row, wherein a back and forth pattern comprises the shape memory alloy wire passing through a first tube in a row, then through an adjacent tube in the row in the opposite direction. Optionally, the patterns described may be repeated through all rows of the substrate. Optionally, the shape memory alloy wire is passes in a back and forth pattern along a first row in a first direction and then in a back and forth pattern along a second row in a second direction, opposite the first direction. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction from a first edge of the substrate to a mid-point of the substrate and then in a back and forth pattern along a second row in a second direction, opposite the first direction from the mid-point of the substrate to the first edge, and a second shape memory alloy wire is knitted in a back and forth pattern along the first row in the second direction from a second edge, opposite the first edge of the substrate, to the mid-point of the substrate and then in a back and forth pattern along the second row in the first direction, from the mid-point of the substrate to the second edge. Optionally, the second row is adjacent the first row. Advantageously, this pattern may be utilised with a hard substrate, for example, a substrate with a shore hardness greater than Al2 or equal to or greater than A20. Optionally, the shape memory alloy wire passes in a back and forth pattern along a first row in a first direction from a mid-point of the substrate to a first edge of the substrate, and a second shape memory alloy wire passes in a back and forth pattern along a second row in a second direction, opposite the first direction from the mid-point to a second edge opposite the first edge of the substrate. Optionally, the second row is adjacent the first row. Optionally, the shape memory alloy wire passes in a back and forth pattern along a first row in a first direction from a first edge of the substrate to a mid-point of the substrate and then in a back and forth pattern along a second row in the first direction, from the mid-point of the substrate to a second edge, opposite the first edge, and a second shape memory alloy wire is knitted in a back and forth pattern along the first row in a second direction, opposite the first direction from the second edge to the mid-point of the substrate and then in a back and forth pattern along the first row in the second direction, from the mid-point of the substrate to the first edge. Optionally, the second row is adjacent the first row. Advantageously, this pattern may be utilised with a soft substrate, for example, a substrate with a shore hardness less than A20 or equal to or less than Al 2. Optionally, the shape memory alloy wire is knitted in a back and forth pattern along a first row in a first direction from a mid-point of the substrate to a second edge and then in a back and forth pattern along a second row in a second direction, opposite the first direction from the second edge of the substrate to the mid-point, and the same shape memory alloy wire is knitted in a back and forth pattern along the second row in the second direction from the mid-point of the substrate, the first edge of the substrate and then in a back and forth pattern along the first row in the first direction, from the first edge of the substrate to the mid-point. Optionally, the second row is adjacent the first row. Optionally, the substrate is compressible. Optionally, the substrate is elastic. Optionally, the substrate is a silicone substrate. Optionally, the shape memory alloy wire is nickel-titanium shape memory alloy wire, for example, a Flexinol® shape memory alloy wire. Optionally, the shape memory alloy wire is temperature actuated, for example, the SMA wire may have an actuation temperate of 90C or 40C. Optionally, the substrate has a melting temperature higher than an activation temperature of the SMA wire. Optionally, the actuation temperature of the shape memory alloy wire is less than 40 degrees. Optionally, the shape memory alloy wire is voltage actuated. Optionally, the SMA wire may be indirectly voltage actuated, for example, the application of voltage to the SMA wire may increase the temperature of the SMA wire to reach the SMA wire actuation temperature. For example, a voltage of 3V or 5V may be applied to the SMA wire to heat the SMA wire and thereby actuate the SMA wire. Optionally, the material may further comprise a chip configured to control voltage applied to the wire. There is further provided a composite material, wherein the composite material has a plurality of zones and each zone comprises a material as described above, and in each zone, the shape memory alloy wire is knitted in a different pattern and / or the substrate is formed of a different material and / or a different shape memory alloy wire is used. The composite material can provide network of compression. Use of modelling can enable the design of a bespoke compression pattern across the composite material for use in the required application. Optionally, when a sensed condition, such as pressure and / or temperature indicates a pre-set condition, a corresponding configuration of the material is caused by supplying a corresponding voltage or set of voltages to the SMA wire(s). Different voltages may be supplied to each SMA wire in the material or composite material to adapt the shoe shape as a whole. There is further provided a shoe, the shoe comprising a material as described above. The material may form part of the insole, sole and / or upper of the shoe. The material within the shoe may advantageously adapt its elasticity and / or shape based on temperature and / or voltage. Where temperature actuation is used, the shoe may adapt to the activity of the user, for example changing the properties of the shoe when the user is running or walking. Optionally, pressure sensors are provided in the shoe and measurements from the pressure sensors are utilised by a chip in the shoe to control the voltage provided to the SMA wire(s) in the material to thereby control the shape and / or elasticity of the material. The chip may be configured to selectively activate the SMA wire(s) in the material based on temperature and / or pressure sensed by sensors within the shoe. For example, when the pressure and / or temperature of the shoe indicates a first condition, for example that the user is running, a first configuration of the material is caused by the chip supplying a first voltage to the SMA wire(s). For example, when the pressure and / or temperature of the shoe indicates a second condition, for example, that the user is walking, a second configuration of the material is caused by supplying a second voltage to the SMA wire(s). Different voltages may be supplied to each SMA wire in the material or composite material to adapt the shoe shape as a whole. This adaptation of the material may be used to adapt the shoe to the user’s foot shape and / or to correct the user’s gait. The shoe may be a sports shoe, such as a training shoe, such as a running shoe. There is further provided a robot, such as a soft robot, the robot comprising a material as described above. There is further provided an artificial muscle, the artificial muscle comprising a material as described above. There is further provided a kit of parts for forming a material, comprising: a substrate, and a shape memory alloy wire, and optionally, instructions for embedding the shape memory alloy wire in the substrate by knitting the shape memory alloy wire into the substrate, for example in a pattern as described above. There is further provided a substrate for use in the above-described method wherein the substrate is suitable for receiving a shape memory alloy wire by knitting the shape memory alloy wire into the substrate. There is further provided a computer-readable medium having computer-executable instructions adapted to cause a 3D printer to print a substrate as described above. The methods, materials, kits and computer-readable mediums described above may be combined in any possible combination. The optional features described above are equally applicable to all of the described methods, materials, kits and computer-readable mediums and are not limited to the particular method, material, kit or computer-readable medium with which they are described here. The essential features of any of the methods, materials, kits and computer-readable mediums described may be optional features of any other method, material, kit or computer-readable medium described. Further features and advantages of the above aspects of the present disclosure will become apparent from the claims and the following description. Brief Description of Drawings Embodiments of the present disclosure will now be described by way of example only, with reference to the following diagrams, in which:- Fig. 1 is a photographic perspective view of a material being manufactured by knitting a SMA wire into a substrate; Fig. 2 is a perspective view of a CAD model of the substrate of Fig. 1; Fig. 3 is a photographic perspective view of the substrate of Fig. 1; Fig. 4 is a side view of a substrate; Fig 5A is a side view of the substrate of Fig. 4 along with arrows indicating a pattern for insertion of a SMA wire; Fig 5B is a side view of the substrate of Fig. 4 along with arrows indicating a pattern for insertion of a SMA wire; Fig 5C is a side view of the substrate of Fig. 4 along with arrows indicating a pattern for insertion of a SMA wire; Fig 5D is a side view of the substrate of Fig. 4 along with arrows indicating a pattern for insertion of a SMA wire; Fig 5E is a side view of the substrate of Fig. 4 along with arrows indicating a pattern for insertion of a SMA wire. Detailed Description A number of different embodiments of the disclosure are described subsequently. In order to minimise repetition, similar features of the different embodiments are numbered with a common two-digit reference numeral and are differentiated by a third digit placed before the two common digits. Such features are structured similarly, operate similarly, and / or have similar functions unless otherwise indicated. Fig. 1 shows a substrate 101 into which a shape memory alloy wire 102 (SMA wire) is being embedded by knitting the SMA wire into the substrate 101 using needle 103. As shown in Fig. 1, the SMA wire is passed through the substrate to thereby knit the SMA wire into the substrate. SMA wire 102 is a Flexinol® SMA wire having a 0.51mm diameter, 90°C and 70°C of activation temperature. The activation temperature is therefore lower than the melting temperature of the silicone substrate, meaning that the SMA wire can be activated without melting the substrate. The SMA wire is also voltage actuated as the application of voltage to the SMA wire increases the temperature of the SMA wire to enable the wire to reach the activation temperature. For example, a voltage of 3 V or 5V may be applied to the SMA wire to heat the SMA wire and thereby actuate the SMA wire. Figs. 2 and 3 show the substrate 101 before the SMA wire is knitted into it. The substrate 101 has holes therethrough, the holes are formed by tubes 104 arranged in rows, and the SMA wire is being passed back and forth through the tubes 104 in a pattern. The substrate 101 is formed by 3D printing / injecting liquid silicone rubber into a soluble PVA negative mould, the silicone having a shore of A20 and A12. The PVA negative mould is then dissolved to leave the substrate. The tubes are arranged so that the direction though tubes in adjacent rows are offset from one another. Tubes in every second row share a common direction and tubes in the intervening rows have a direction common to each other. This can be seen more clearly in Figs. 2 and 3, in which tubes 104a in a first row share a common direction and tubes 104b share a common direction. The directions of the tubes are diagonal to a face of the substrate in an arrangement named opposite diagonal tubing. The tubes have a diameter of 0.4cm and thickness of 0.12cm and a distance between tube centres of 0.6cm. Further reinforcement of the connections between tubes is given by 0.14cm diameter rods. Different knitting patterns may be implemented to cause the material to act in a desired manner. Some examples of knitting patterns will be described with reference to Figs. SASE, but are equally applicable to the material of Figs. 1-3. Fig. 4 shows another substrate 201. The material and configuration of tubes 204a, 204b is the same as the substrate shown in Figs. 1 to 3, but only two rows of tubes are present. Further, two measurement attachments 205 are provided at opposing ends of the substrate 201 to allow testing of the properties of the substrate 201. The patterns have been produced and tested by the inventors using the Flexinol® SMA wire described above, but are equally applicable to other SMA wires and substrates. Figs. 5A to 5B show example knitting patterns for SMA wire through substrate 201. Each pattern gives the resulting material a respective set of properties when the SMA wire is activated. The substrate 201 has a 60mm length (shown left to right in Fig. 4), 22.5mm height (into and out of the page in Fig. 4) and (shown top to bottom in Fig. 4}8mm width. The SMA wire is knitted in a back and forth pattern along a row. The SMA wire passes through a first tube in a row, then through an adjacent tube in the row in the opposite direction. The arrows in the patterns of Fig. 5A-5E show the direction of the adjacent tube in the row. In these figures, the right edge of the substrate is the first edge and the left edge of the substrate is the second edge, the first direction is left to right and the second direction is right to left, the first row is the top row and the second row is the bottom row or the row beneath the first row. In the pattern shown in Fig. 5A, the shape memory alloy wire passes in a back and forth pattern along the top row in a direction left to right, and then in a back and forth pattern along the bottom row from right to left. In the pattern shown in Fig. 5B, the shape memory alloy wire passes in a back and forth pattern along the top row in a direction left to right from a mid-point Ml of the substrate to the right edge. The same shape memory alloy wire passes in a back and forth pattern along the bottom row from right to left from the mid-point Ml to the left edge. In the pattern shown in Fig. 5C, the shape memory alloy wire is knitted in a back and forth pattern along the top row in a direction left to right from the left edge, to a mid-point M2 of the substrate and then in a back and forth pattern along the bottom row from right to left from the mid-point M2 of the substrate to the left edge. A second shape memory alloy wire is knitted in a back and forth pattern along the top row from right to left from the right edge, to the mid-point M2 of the substrate and then in a back and forth pattern along the bottom row from in a direction left to right, from the mid-point M2 of the substrate to the first, right edge. In the pattern shown in Fig. 5D, the shape memory alloy wire passes in a back and forth pattern along the top row in a direction left to right from the left edge to a mid-point M3 of the substrate and then in a back and forth pattern along the bottom row in a direction left to right, from the mid-point M3 of the substrate to the right edge. A second shape memory alloy wire is knitted in a back and forth pattern along the top row in a direction right to left, from the right edge to the mid-point M3 of the substrate and then in a back and forth pattern along the bottom row in a direction right to left, from the mid-point M3 of the substrate to the left edge. In the pattern shown in Fig. 5E, the shape memory alloy wire is knitted in a back and forth pattern along a top row, a direction left to right from a mid-point M4 of the substrate to a right edge and then in a back and forth pattern along the bottom row, in a direction right to left from the right edge of the substrate to the mid-point M4. The same shape memory alloy wire is knitted in a back and forth pattern along the bottom row in a direction right to left from the mid-point M4 of the substrate to the left edge of the substrate and then in a back and forth pattern along the top row in a direction left to right, from the left edge of the substrate to the mid-point M4. The inventors have found during testing that each of the above example patterns produce a significant change in elasticity of the material between the actuated and unactuated state of the SMA wire(s). As described, the SMA wire in the material may be activated by temperature and / or voltage. In some embodiments, the material further comprises a chip configured to control voltage applied to the wire. In this way, the chip can determine when to activate the SMA wire and provide and / or adjust the required voltage accordingly. The chip may change the voltage dependent on time, measured pressure, temperature or other sensed parameters. A composite material can be formed with a plurality of zones and in each zone an SMA wire is knitted into a substrate. In each zone, the shape memory alloy wire is knitted in a different pattern and / or the substrate is formed of a different material and / or a different shape memory alloy wire is used. The formation of a composite material can enable a network of compression to be formed across the composite material and modelling can enable the design of a bespoke compression pattern across the composite material for use in the required application. One example of an application for the above-described material is in footwear, for example in a shoe such as a running shoe. In one example, the material forms part of the midsole of the running shoe. Pressure sensors are also provided in the shoe and measurements from the pressure sensors are provided to a chip. The material within the shoe is controlled by the attached chip, the chip configured to selectively activate the SMA wire(s) in the material based on temperature and / or pressure sensed by sensors within the shoe. When the pressure and / or temperature of the shoe indicates that the user is running, a first 'running’ configuration of the material is caused by supplying a first voltage to the SMA wire. When the pressure and / or temperature of the shoe indicates that the user is walking, a second 'walking’ configuration of the material is caused by supplying a second voltage to the SMA wire. The use of this material may enable the shoe to adapt its shape to the user’s foot shape and / or to correct the user’s gait. Although particular embodiments of the disclosure have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims. For example, different SMA wires, substrate materials, arrangement of tubes / holes, sizes of substrate, sizes of SMA wire and / or knitting patterns can be implemented within the scope of the invention. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the scope of the invention as defined by the claims.

Claims

1)    A method of manufacture of a material, the method comprising:providing a substrate,providing a shape memory alloy wire, andknitting the shape memory alloy wire through the substrate.2) A method according to claim 1, wherein the substrate has holes therethrough and knitting the shape memory alloy wire through the substrate comprises passing the shape memory alloy wire through a subset of the holes.3) A method according to claim 2, wherein the holes are formed by tubes arranged in rows, the wire being passable through the tubes.4) A method according to claim 3, wherein the shape memory alloy wire is knitted in a back and forth pattern along a row, wherein a back and forth pattern comprises the shape memory alloy wire being passed through a first tube in a row, then through an adjacent tube in the row in the opposite direction, and repeating this pattern.5) A method according to any preceding claim, wherein the substrate is elastic.6) A method according to any preceding claim, wherein the substrate is a silicone substrate.7) A method according to any preceding claim, wherein the shape memory alloy wire is nickel-titanium shape memory alloy wire.8) A method according to any preceding claim, wherein the shape memory alloy wire is temperature actuated.9) A method according to any preceding claim, wherein the substrate has a melting temperature higher than an activation temperature of the shape memory alloy wire.10] A method according to any preceding claim, wherein the actuation temperature of the shape memory alloy wire is less than 40 degrees.11) A method according to any preceding claim, wherein the shape memory alloy wire is voltage actuated.12) A method of manufacture of a composite material, wherein the composite material has a plurality of zones and in each zone a method according to any one of claims 1 to 11 is performed, wherein in each zone, the shape memory alloy wire is knitted in a different pattern and / or a different substrate is present and / or a different shape memory alloy wire is used.13) A material, the material comprising:a substrate, anda shape memory alloy wire, wherein the shape memory alloy wire is knitted through the substrate.14) A material according to claim 13, wherein the substrate has holes therethrough and the shape memory alloy wire passes through a subset of the holes.15) A material according to claim 14, wherein the holes are formed by tubes arranged in rows, the wire being passable through the tubes.16) A material according to claim 15, wherein the shape memory alloy wire is knitted in a back and forth pattern along a row, wherein a back and forth pattern comprises the shape memory alloy wire being passed through a first tube in a row, then through an adjacent tube in the row in the opposite direction, and repeating this pattern.17) A material according to any one of claims 13 to 16, wherein the substrate is elastic.18) A material according to any one of claims 13 to 17, wherein the substrate is a silicone substrate.19) A material according to any one of claims 13 to 18, wherein the shape memory alloy wire is nickel-titanium shape memory alloy wire.20) A material according to any one of claims 13 to 19, wherein the shape memory alloy wire is temperature actuated.21) A material according to claim 20, wherein the substrate has a melting temperature higher than an activation temperature of the shape memory alloy wire.22) A shoe, the shoe comprising a material according to any of claims 13 to 21.23) A kit of parts for forming a material, comprising: a substrate, and a shape memory alloy wire, and optionally, instructions for embedding the shape memory alloy wire in the substrate by knitting the shape memory alloy wire into the substrate.

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