Electronic unit for a textile

Abstract

An electronic unit for incorporating into a textile to provide the textile with electronic capability, the electronic unit 110 comprising: a non-conductive helical substrate 112; one or more conductiv

Description

FIELD OF INVENTION The present invention relates to an electronic unit for incorporating into a textile to provide the textile with electronic capabilities, and in particular but not exclusively, to a flexible and stretchable electronic unit for incorporating into a textile to provide the textile with electronic capabilities. BACKGROUND Garments and textiles having electronic capabilities are becoming increasingly common. Such garments are often used for such purposes as monitoring of the wearer of the garment, for example using sensors mounted on the garment. In the fields of medicine and professional sport, monitoring of an individual in situ has the potential to provide invaluable information, for example to improve the reliability of a diagnosis or to improve performance. However, garments having electronic capabilities are typically heavier and more restrictive for a wearer than conventional garments. That can be due to one or more of size, weight or location of any sensors, connectors, other electronic components, or circuitry mounted on the garment, or the mechanical properties of any sensors, connectors, other electronic components, or circuitry (for example, stiffness, rigidity). A common issue with electronic components currently available is that they lack flexibility and stretchability. Garments or textiles which are excessively large or heavy, or garments comprising rigid, non-flexible sections, may restrict movement of a wearer or user and may inhibit normal activity or performance of the wearer or user. Further, some garments or textiles may only be flexible in certain directions. For example, the wearer or user may have to exert more effort when wearing the garment in order to achieve his or her normal or typical standard of activity or performance. In turn, the garment or textile may therefore not provide an accurate or reliable indication of the activity or performance of the wearer or user. In addition, such garments or textiles can be uncomfortable for the wearer or user. The present invention has been devised with the foregoing in mind. SUMMARY OF INVENTION According to a first aspect, there is provided an electronic unit for incorporating into a textile to provide the textile with electronic capability. The electronic unit may comprise a non-conductive helical substrate. The electronic unit may comprise one or more conductive tracks disposed on the substrate. A helical substrate provides a “spring-like” effect for the electronic unit. This may improve the flexibility and stretchability of the electronic unit. A helical substrate may significantly increase the stretchability of the electronic unit relative to an electronic unit comprising a conventional planar or non-helical substrate (for example, the electronic unit may be able to stretch to increase its length by over 40%), without requiring the substrate material itself to be stretchable. In addition, a helical substrate may provide the electronic unit with significant flexibility in substantially all directions (for example, both in-plane bending and out-of-plane bending). A helical substrate may enable the electronic unit to achieve a bending radius substantially equal to or smaller than a cross-sectional diameter of the helical substrate, in substantially all bending directions. Those performance improvements may be beneficial for electronic units incorporated into textiles, such as garments, allowing the electronic unit to bend and deform to follow movement of the textile into which it is incorporated. In addition, a helical substrate may have a greater surface area than a conventional planar substrate over a given length. That may enable a greater area of circuitry to be included in an electronic unit having a helical substrate. That may improve a functionality of the electronic unit compared to conventional electronic units of a comparable length, or may enable a similar functionality to be provided in an electronic unit having a substantially shorter length. The non-conductive helical substrate may define a central region extending through the helical substrate. One or more of the conductive tracks may be disposed on a side of the non-conductive helical substrate facing the central region. Each of the one or more conductive tracks may be disposed on the side of the non-conductive helical substrate facing the central region. Disposing conductive tracks on an inner surface of the helical substrate (the side of the substrate facing toward the central region defined by the helix) may protect the conductive tracks from being damaged. The side of the helical substrate facing the central region of the helix may be less exposed to damage from, for example, external forces and contaminants. The conductive tracks may be or comprise flexible conductive tracks. The conductive tracks may be or comprise a conductive ink. Flexible conductive tracks (for example, conductive ink tracks) may prevent the conductive tracks from breaking, snapping, or coming loose from the substrate as the helical substrate deforms by stretching or flexing. The electronic unit may further comprise one or more electronic components mounted on and connected to one or more of the conductive tracks. The electronic components may be or comprise flexible components. The electronic components may be or comprise printed flexible components. The presence of electronic components may enable the electronic unit to provide a desired functionality, for example as a sensor, a battery, a display, an energy harvester, an actuator etc. Flexible electronic components (for example, printed electronic components) may prevent the electronic components from breaking, snapping, or coming loose from the conductive tracks as the helical substrate deforms by stretching or flexing. The electronic components may be or comprise connectors. The connectors may enable the electronic unit to be connected to external circuitry, such as external PCBs and power supplies, and / or to another electronic unit. Further, the connectors may enable the electronic unit to act as an interconnect for connecting one or more external circuits. The electronic unit may further comprise a core. The core may extend through or along at least a portion of the central region of the non-conductive helical substrate. The core may extend through the entire central region of the helical substrate. The core may extend through and beyond the entire central region of the helical substrate, such that the ends of the core are located outside of the central region of the helical substrate. The core may extend through only a portion of the helical substrate, such that one or both ends of the core are located within the central region. At least a portion of the helical substrate may be disposed on, or supported by, the core. The core may abut or contact the inner surface of the helical substrate. The core may abut the inner surface of the helical substrate such that the helical substrate compresses the core, for example in response to mechanical stresses or deformation of the helical substrate. The core may help the helical substrate to retain its shape. For example, the core may prevent the helix from collapsing and losing the central region following bending or stretching. The core may also protect the conductive tracks and / or the electronic components disposed on the inner surface of the helical substrate from damage, for example due to mechanical stresses or contamination. The core may be flexible and / or stretchable. The core may also be compressible. The core may be or comprise foam. The core may be or comprise neoprene foam, EPDM foam, or silicone foam. The core may alternatively be or comprise a stretchable polymer or a textile. A flexible and / or stretchable core may enable the electronic unit to stretch and flex, as the core will deform along with the helical substrate. A flexible and / or stretchable core may prevent the core from snapping and / or breaking. A compressible core may provide additional protection to any conductive tracks and / or electronic components disposed on the inner surface of the helical substrate. The core may be or comprise a substantially cylindrical shape. The core may be or comprise a different shape. The shape of the core may substantially correspond to the shape of the central region of the helical substrate. For example, a cross-section of the core may be ovular or elliptical to substantially correspond to an ovular or elliptical cross-section of the central region of the helical substrate. The core may comprise a thickness or diameter of between substantially 2mm and substantially 10mm, preferably between substantially 2mm and substantially 5mm. A core having such a thickness or diameter may enable the electronic unit to be small enough to be discrete when incorporated into a textile (for example, to avoid inhibiting movement of the textile during use), but large enough to prevent or inhibit delamination of or damage to the conductive tracks (or any electronic components mounted on the conductive tracks) due to a curvature of the helical substrate surface. The non-conductive helical substrate may be formed from or comprise a flexible material. The non-conductive helical substrate may be formed from or comprise a polymeric or plastic material. The polymeric or plastic material may be a polymeric or plastic film material. The non-conductive helical substrate may be made from or comprise polyimide or polyethylene terephthalate. The non-conductive helical substrate may comprise an angled end. The angled end may be angled relative to a longitudinal axis of a planar tape or strip from which the non-conductive helical substrate is formed. The angled end may be configured to be aligned substantially parallel to a longitudinal axis of the non-conductive helical substrate when formed. The angled end may act to guide wrapping or winding of the non-conductive helical substrate at a correct (for example, desired or intended) wrapping or winding angle). The angled end may also enable an external connector to be attached to the electronic unit substantially parallel to a longitudinal axis of the non-conductive helical substrate. The electronic unit may comprise an encapsulation layer. The encapsulation layer may form a protective coating around or over the substrate and the conductive tracks. The encapsulation layer may be made from or comprise a stretchable adhesive, a thermoplastic or a braided yarn. The encapsulation layer may provide a protective coating for the helical substrate, the conductive tracks and / or the electronic components. The encapsulation layer may prevent damage by mechanical forces or contaminants. The electronic unit may comprise two encapsulation layers. The first encapsulation layer may provide a protective coating for the inner surface of the helical substrate and the conductive tracks (and electronic components, if present). The second encapsulation layer may provide a protective coating that surrounds the entire helical substrate together with the core (if present). According to a second aspect, there is provided a textile comprising the electronic unit of the first aspect. According to a third aspect, there is provided a garment comprising the electronic unit of the first aspect or the textile of the second aspect. According to a fourth aspect, there is provided a method of forming an electronic unit for incorporating into a textile to provide the textile with electronic capability. The method may comprise disposing one or more conductive tracks onto a non-conductive substrate. The method may further comprise forming the substrate into a helix. The method of the fourth aspect may be used to produce the electronic unit of the first aspect of the invention. Forming the substrate into a helix may comprise winding the substrate around a core. The method may comprise disposing a core into a central region defined by the helix. Disposing the core into the central region may comprise injection moulding the core into the central region. The method may comprise applying an adhesive between the helical substrate and the core. The adhesive may be applied to the core. The adhesive may be applied to the helical substrate. The adhesive may be applied to the core and the helical substrate. The adhesive between the core and the helical substrate may maintain the contact between the core and the helical substrate. This, in turn, may help to maintain the helical shape of the substrate, and may help to protect the conductive tracks and the electronic components disposed on the helical substrate. The method may comprise applying an encapsulation layer around or over the substrate. Applying the encapsulation layer may comprise vacuum forming, dispensing, dipping, spray coating or braiding yarn. The method may comprise applying first and second encapsulation layers. The first and second encapsulation layers may be applied separately. The first and second encapsulation layers may be applied using any of the encapsulation methods described above. The first encapsulation layer may be applied to the substrate before it is formed into a helix. The first encapsulation layer may only be applied to the side of the substrate which forms the inner surface of the helix. The second encapsulation layer may be applied after the substrate is formed into a helix. The second encapsulation layer may be applied over the entire helical substrate and the core (if present). Optional features of any of the above aspects may be combined with the features of any other aspect, in any combination. For example, features described in connection with the electronic unit of the first aspect may have corresponding features definable with respect to the method of the fourth aspect, and vice versa, and these embodiments are specifically envisaged. Features which are described in the context or separate aspects and embodiments of the invention may be used together and / or be interchangeable wherever possible. Similarly, where features are, for brevity, described in the context of a single embodiment, those features may also be provided separately or in any suitable sub-combination. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example with reference to the accompanying drawings in which: FIGs. 1A-1C show an electronic unit comprising a helical substrate, according to an embodiment of the present invention; FIG. 2 shows an electronic unit comprising a helical substrate and a core extending through a central region of the helical substrate, according to another embodiment of the present invention; FIGs. 3A and 3B show an electronic unit comprising a helical substrate comprising an angled end, according to another embodiment of the present invention; FIGs. 4A and 4B show helical electronic units of the present invention compared with conventional non-helical electronic units; FIGs. 5A-5C show the respective stretchability of the electronic units shown in FIG. 4A; FIGs. 6A-6C show the respective stretchability of the electronic units shown in FIG. 4B; FIGs. 7A-7C show the respective in-plane flexibility of the electronic units shown in FIGs. 4A and 4B; FIGs. 8A-8C show the respective out-of-plane flexibility of the electronic units shown in FIGs. 4A and 4B; and FIG. 9 shows a method for manufacturing an electronic unit comprising a helical substrate, according to an embodiment of the present invention. Like reference numbers and designations in the various drawings may indicate like elements. DETAILED DESCRIPTION For the purposes of this specification, the term “flexibility” refers to the ability of an object or material to accommodate deformation (for example, bend or twist) without breaking or becoming damaged, whilst the term “stretchability” refers to the ability of an object or material to reversibly increase in length and / or width. Figures 1A to IC show an electronic unit 10 for incorporating into a garment to provide the garment with electronic capability, according to an embodiment of the present invention. The electronic unit 10 comprises a non-conductive helical substrate 12. One or more conductive tracks 14 are disposed on the substrate 12. The conductive tracks 14 can be disposed, formed or fabricated on the substrate 12 using additive (e.g.. deposition) or subtractive (e.g., etching) manufacturing methods. The substrate 12 comprises a flexible substrate material and is wound into the shape of a helix. In the embodiment shown, the helical substrate 12 is or comprises polyimide, although that is not essential. Alternatively, the helical substrate 12 may be or comprise a different plastic or polymer material such as polyethylene terephthalate (PET), PVC, polyamide, PMMA etc. Alternatively, the helical substrate 12 may be or comprise a fabric or textile. The fabric or textile may be woven, non-woven, knitted etc., and may optionally be coated. The coating may be a waterproof coating. Additionally or alternatively, the coating may have a different functionality. For example, the coating may be configured to absorb infra-red radiation. The coating may be formed form, or comprise, a material which absorbs infra-red radiation. In the embodiment shown, the helical substrate 12 defines or comprises a central region 11. The central region 11 extends through the helical substrate 12 along a longitudinal axis of the helical substrate 12 (for example, along a length of the electronic unit 10). The helical substrate 12 may be considered as substantially surrounding the central region 11 it defines. The helical substrate 12 comprises an inner surface 13. The inner surface 13 is internal to the helix shape, adjacent or facing towards the central region 11 defined by the helix shape. The helical substrate 12 also comprises an outer surface 15. The outer surface 15 is external to the helix shape, facing away from the central region 11. In the embodiment shown, the helical substrate 12 is formed by a length of substrate material in the form of a tape or strip having a substantially planar construction. Such a tape or strip may have clearly defined opposing surfaces forming the inner surface 13 and outer surface 15 of the helical substrate. Alternatively, the helical substrate 12 may be formed by a length of substrate material in the form of a yarn or thread, which may have a more cylindrical or elliptical cross-section than a substantially planar tape or strip. However, such a helical substrate 12 may still comprise an inner surface 13 substantially facing towards the central region 11 defined by the helix shape, and an outer surface 15 substantially facing away from the central region 11. The central region 11 of the helix has a substantially circular cross-section. This is typical of a standard helix. However, in alternative examples, the central region 11 may not have a circular cross-section. For example, the cross-section could be ovular or elliptical. In the embodiment shown, two conductive tracks 14 are disposed on the inner surface 13 of the helical substrate 12. Alternatively, the electronic unit 10 may comprise a single conductive track 14, or may comprise any number (for example, three, four, five or more) of conductive tracks 14 disposed on the helical substrate 12. The number of conductive tracks 14 may be determined by the function the electronic unit 10 is intended to perform, or the number of electrical connections required to be formed using the conductive tracks 14. One or more conductive tracks 14 may additionally or alternatively be disposed on the outer surface of the helical substrate 12. In embodiments where one or more of the conductive tracks 14 are disposed on the outer surface of the helical substrate 12, those one or more conductive tracks 14 may be used for electromagnetic shielding (EMF) and / or electrostatic discharge (ESD). In the embodiment shown, the conductive tracks 14 form a substantially straight line. Alternatively, the conductive tracks 14 can be arranged in alternative shapes, such as a horseshoe shape, or a meandering or serpentine shape, or an irregular line. That may provide the conductive tracks 14 with flexibility and may enable the conductive tracks to accommodate movement (such as bending, twisting, stretching etc.) of the helical substrate 12. Alternatively, the conductive tracks 14 may be formed from a flexible material. In the embodiment shown, the conductive tracks 14 are or comprise a conductive ink, although any suitable conductive material, such as copper and other metals, may alternatively be used. Although they are not shown, one or more electronic or electrical components may be disposed on the conductive tracks 14. The electronic components may be conventional electronic components. The electronic components may be attached to the conductive tracks 14 in any suitable manner. For example, the electronic components may be soldered to the conductive tracks 14 or may be adhered to the conductive tracks using a conductive adhesive (for example, an anisotropic conductive adhesive). Alternatively, the electronic components may be flexible components which are printed onto the conductive tracks 14. An electronic unit 10 without electronic components disposed on the conductive tracks 14 may be used as an electrical interconnect, for example between external circuits (e.g., planar flexible circuit boards) disposed on or within a garment. The conductive tracks 14 may be soldered or otherwise adhered to one or more electrical contacts on the external circuit. Alternatively, one or more electronic components disposed on the conductive tracks 14 may be or comprise a connector that may be enable the electronic unit to be connected to one or more external circuits. Alternatively, an electronic unit 10 comprising electronic components disposed on the conductive tracks 14 may provide a specific functionality depending on the electronic components disposed on the conductive tracks 14. For example, the electronic components disposed on the conductive tracks 14 may enable the electronic unit 10 to function as one or more of a sensor, a battery, a display, an antenna, an energy harvester or an actuator in a garment with electronic capability. Such electronic units 10 may, for example, be used for performance monitoring or activity tracking in sportswear garments, or as sensors and / or actuators for monitoring treatment delivery in medical textiles or garments, or as sensors and / or actuators / displays / radio frequency communication for improving combat efficiency in military textiles or garments. The helical shape of the substrate 12 increases the flexibility and stretchability of the electronic unit 10. Figure IC shows the electronic unit 10 in an unstretched or rest state. Figure IB shows the electronic unit 10 in a partially stretched state. Figure 1A shows the electronic unit 10 in a further (for example, fully) stretched state. Figure 2 shows another electronic unit 110, according to another embodiment of the present invention. The electronic unit 110 is substantially similar to the electronic unit 10 shown in Figures 1A to IC, with like reference numerals indicating like elements. The electronic unit 110 further comprises a core 116. In the embodiment shown, the core 116 extends through or along a part of the central region 111 of the electronic unit 110, although that is not essential. Alternatively, the core 116 may extend fully through or along the central region 111. The length of the core 116 may be longer, shorter or substantially the same length as the length of the helical substrate 112 (for example, the length along the longitudinal axis of the helix). In the embodiment shown, the core 116 is formed from a foam material. In particular, the core 116 is formed using neoprene foam. The neoprene foam core 116 is compressible, flexible and stretchable. Flexibility of the foam core 116 may prevent the core 116 from restricting movement (for example, bending or stretching) of the helical substrate 112. Compressibility of the foam core 116 may enable the core 116 to provide protection to any electronic components mounted on conductive tracks 114 on the inner surface 113 of the helical substrate 112, by providing a compressible surface for the electronic components to contact. Stretchability of the foam core 116 may enable the core 116 to stretch with the helical substrate 112. Alternatively, the core 116 could be formed using another type of foam, such as ethylene propylene diene monomer (EPDM) foam or silicone foam. Alternatively, the core 116 could be formed from a textile, such as a knitted fabric, or a stretchable plastic, rubber, or polymeric material. The core 116 may alternatively be formed from or comprise any suitable flexible or stretchable material, and optionally from any suitable material that is flexible and stretchable and / or compressible. The core 116 is substantially cylindrical in the embodiment shown, having a substantially circular cross-section, although that is not essential. Alternatively, the core 116 may have a substantially elliptical cross-section. The cross-section of the core 116 may correspond with the cross-section of the helical substrate 112 and the central region 111. The core 116 may be used to form the helix shape of the helical substrate 112. For example, a length of the substrate 112 may be wrapped and / or wound around the core 116 to form a helix shape. The substrate 112 may retain a helical shape after being wrapped or wound around the core 116. Although it is not shown in Figure 2, the inner surface 113 may be disposed on or contact the core 116. This may enable the core 116 to abut and protect electronic components and / or conductive tracks disposed on the helical substrate 112. Further, the core 116 may help to maintain the helical shape of the substrate 112 and prevent the substrate 112 from being damaged by mechanical stresses. An adhesive (for example, a layer of adhesive) may be disposed between the inner surface 113 of the substrate 112 and the core 116. The adhesive may maintain the connection between the core 116 and the substrate 112 after the substrate 112 is wound into its helical shape around the core 116. Alternatively, the electronic unit 110 may not comprise an adhesive between the core 116 and the helical substrate 112. Alternatively, the substrate 112 may be wound into a helical shape independently of or separately from the core 116. For example, a coating may be applied to one side of the substrate 112. The coating may be applied to the substrate 112 in a predetermined pattern. The coating may be configured to contract when cured in order to bend the substrate 112 into a helical shape. The coating may create a tension difference between the two sides of the substrate 112, causing the substrate to twist and / or bend into a helical shape. The core 116 may then be disposed within the central region 111 of the helical substrate 112. For example, the core 116 may be injection moulded into the central region 111 of the helix. In examples where the core 116 is formed by injection moulding, the core 116 may be formed from a stretchable polymer, such as thermoplastic polyurethane (TPU) or thermoplastic rubber (TPR). An adhesive may be applied to one or both of the helical substrate 112 and the core 116 prior to disposing the core 116 within the central region 111 of the helical substrate 112. The electronic unit 110 also comprises an encapsulation layer 118. The encapsulation layer 118 substantially surrounds and / or encapsulates the helical substrate 112 and the core 116. The encapsulation layer 118 acts as a protective seal to contain the substrate 112 together with the conductive tracks 114 and any electronic or electrical components disposed thereon. The encapsulation layer 118 may protect the substrate 112 from water ingress, for example during washing of a garment in which the electronic strip 110 is incorporated, or during sweating of a wearer of the garment. The encapsulation layer 118 may also protect the substrate 112 from mechanical damage caused by dust or other foreign objects, and / or from impact forces (for example if the garment is used by a wearer playing contact sports). In the embodiment shown, the encapsulation layer 118 is applied across a part of the length of the helical substrate 12. Alternatively, the encapsulation layer 118 may be applied substantially along the entire length of the helical substrate 112 and the core 116. Alternatively, the encapsulation layer 118 may comprise a plurality of separate portions with a gap between adjacent portions. That may enable the encapsulation layer 118 to cover one or more separate portions of the helical substrate 112 and the core 116. The gaps may be present at portions or locations of the substrate 112 where it is desirable to expose the conductive tracks to form electrical connections with external components. The encapsulation layer 118 may have a shorter length than the helical substrate 112 such that the ends of the substrate are not covered by the encapsulation layer 118. This may be desirable as it can enable the ends of the electronic unit 110 to be electrically connected to external components. The encapsulation layer 118 may be applied to the substrate 112 so that it initially covers the entire substrate 112, and sections of the encapsulation layer 118 may then be subsequently removed, for example to expose one or more conductive tracks 114 for electrical connection. In the embodiment shown, the encapsulation layer 118 comprises a layer of dielectric material. However, this is not essential, and the encapsulation layer 118 may be formed from any non-conductive material. The encapsulation layer 118 may be formed from, or comprise, a substantially stretchable material which may enable the encapsulation layer 118 to stretch together with the helical substrate 112 (and optionally the core 116). The encapsulation layer 118 may be or comprise a stretchable adhesive, such as a flexible polymer adhesive. The adhesive may be UV or thermally curable, or may comprise a two-part adhesive (for example, a resin and a hardener) that cures or bonds via a chemical reaction between the two parts. Alternatively, the encapsulation layer 118 may be or comprise a thermoplastic material, or braided yarn disposed around the helical substrate 112. In some embodiments, the encapsulation layer 118 can be formed from or comprise the same material as the helical substrate 112. The encapsulation layer 118 may be applied to the substrate by vacuum forming (i.e., the encapsulation layer 118 may be vacuum formed over the substrate 112). Alternatively, the encapsulation layer 118 may be formed by spraying a coating onto the substrate 112, or by dipping the substrate 112 into a liquid which dries to form the encapsulation layer 118. The encapsulation layer 118 may be bonded to the substrate 112 through a chemical reaction between the encapsulation layer 118 and the substrate 112. After being applied to the substrate 112, the encapsulation layer 118 may be cured (or at least partially cured). Curing of the encapsulation layer 118 may take place at room temperature or at an elevated temperature (for example between substantially 80°C and substantially 200°C). Alternatively or additionally, curing may comprise irradiation with UV light. Figures 3A and 3B show another electronic unit 150, according to another embodiment of the present invention. The electronic unit 150 is substantially similar to the electronic units 10, 110 shown in Figures 1A to IC and 2. The helical substrate 152 comprises an angled end 152a. The angled end 152a is angled relative to a longitudinal axis of a planar tape or strip from which the helical substrate 152 is formed. The angled 152a may act to guide wrapping or winding of the planar tape or strip at a correct (for example, desired or intended) wrapping or winding angle to form the helical substrate 152, as shown in Figure 3B. The angled end 152a may be aligned substantially parallel to a longitudinal axis of the helical substrate 152 when formed, for example substantially parallel to a longitudinal axis of a core 156 around which the planar tape or strip is wrapped or wound. That may enable an external connector to be attached to the electronic unit 150 substantially parallel to a longitudinal axis of the helical substrate 152. In the embodiment shown, one or more of the conductive tracks 154 extend onto the angled end 152a into one or more connection points 152b (for example, solder pads) for forming a connection to an external connector. In the embodiment shown, the connection points 152b comprise a greater width than the conductive tracks 154 to provide an increased area for forming a connection, although that is not essential. Figures 4A and 4B show electronic units 210, 310 each comprising a helical substrate, next to conventional, non-helical electronic units 220, 320 comprising a substantially planar substrate. These electronic units 210, 310, 220, 320 demonstrate the advantageous effects of a helical substrate as used in the present invention. In Figure 4A, the electronic units 210, 220 each comprise two conductive tracks disposed on a polyimide film substrate. The conductive tracks run substantially parallel with each other. The electronic units 210, 220 are formed using the same substrate material. However, in the electronic unit 210, the polyimide substrate is wound around a 2mm diameter EPDM foam core to form a helix, whereas in the conventional electronic unit 220 the substrate comprises a planar shape or construction. In Figure 4B, the electronic units 310, 320 each comprise two conductive tracks disposed on a polyimide film substrate, with an LED provided at one end of the substrate. The electronic units 310, 320 are formed using the same substrate material. However, in the electronic unit 310, the polyimide substrate is wound around a 5mm diameter EPDM foam core to form a helix, whereas in the conventional electronic unit 320 the substrate comprises a planar shape or construction. The helical electronic units 210, 310 have a greater surface area than conventional nonhelical electronic units 220, 320 over a given length. That may enable a greater area of circuitry (for example, conductive tracks and / or electronic components) for a helical electronic unit 210, 310 compared to a planar electronic unit 220, 320 having the same length. That may improve the functionality of the helical electronic units 210, 310 compared to conventional electronic units 220, 320 of a comparable length, or may enable similar functionality to be provided in an electronic unit 210, 310 having a substantially shorter length than a conventional non-helical electronic unit 220, 320. Figures 5A and 6A respectively show the conventional electronic units 220, 320 in an apparatus configured to apply tensile force to try to stretch the electronic units 220, 320. The electronic units 220, 320 are connected at a first point to a first connector (e.g., pair of jaws) and at a second point to a second connector (e.g., pair of jaws). Polyimide, which the substrates for both the electronic units 220, 320 are formed from, is not inherently stretchable. As such, on the application of tensile force, the electronic units 220, 320 exhibit substantially no stretchability. Figures 5B and 5C show the electronic unit 210 in the same apparatus. Figure 5B shows the electronic unit 210 before the application of tensile force, with a resting or unstretched length of 70mm. Figure 5C shows the electronic unit 210 after being stretched to 100mm on the application of tensile force. The electronic unit 210 is stretched to increase its length by 30mm. The helical electronic unit 210 therefore has significantly increased stretchability when compared with a conventional non-helical electronic unit 220, despite the substrates of both the electronic units 210, 220 being made from the same material. The electronic unit 210 is able to stretch to increase its length by over substantially 40% (approximately 43%), thereby exhibiting far greater stretchability than associated with the inherent properties of polyimide (which exhibits virtually no stretchability). Similarly, Figures 6B and 6C show the electronic unit 310 in the same apparatus. Figure 6B shows the electronic unit 310 before the application of tensile force, with a length of 50mm. Figure 6C shows the electronic unit 310 after being stretched to 70mm. As such, the electronic unit 310 stretched to increase its length by 20mm (an increase in length of substantially 40%). As for the helical electronic unit 210, the helical electronic unit 310 has significantly increased stretchability when compared with a conventional non-helical electronic unit 320. The improved stretchability of electronic units 210, 310 may be enabled by the helical shape of the substrates of the electronics units 210, 310. The helical substrates of the electronic units 210, 310 may act substantially similarly to a spring. Figures 7A-C demonstrate the in-plane flexibility of the helical electronic units 210, 310 and the conventional planar electronic unit 320. In that regard, the term “in-plane flexibility” refers to the ability of the electronic unit to deform in a direction lying in the plane of the substrate of the electronic unit. Those directions are respectively labelled as the x and y axes in Figures 7A-C. Figure 7A shows the electronic unit 320 after being bent in the x-y plane. Figure 7A demonstrates that, even when subject to a small bending angle (approximately 8° in Figure 7A), the electronic unit 320 begins to buckle, forming a kink 22. As such, the electronic unit 320 has little to no flexibility in the x-y plane. The formation and presence of the kink 22 can also damage the electronic unit 320, for example, the substrate, conductive tracks or electronic components disposed thereon. By contrast, Figures 7B and 7C respectively show the electronic units 310, 210 after being bent in the x-y plane. Figures 7B and 7C demonstrate that, even when subjected to a large bending angle (approximately 180° in Figures 7B and 7C), the helical electronic units 210, 310 do not buckle and no kinks are formed. The bending radius of the electronic unit 310 is approximately 5mm, indicated by the horizontal line extending in from the edge of the circle shape annotation on Figure 7B. The bending radius of the electronic unit 210 is approximately 2mm, indicated by the horizontal line extending in from the edge of the circle shape annotation on Figure 7C. As such, the electronic units 210, 310 exhibit high levels of flexibility in the x-y plane. That may reduce a risk of damage to the electronic units 210, 310 (and constituent components) even at large inplane bending angles, unlike for the conventional electronic unit 320. Figures 8A-C demonstrate the out-of-plane flexibility of the helical electronic units 210, 310 and the conventional electronic unit 320. In that regard, “out-of-plane flexibility” refers to the ability of the electronic unit to deform in a direction not lying in the plane of the substrate of the electronic unit. That direction is labelled as the z-axis in Figures 8A-C. Figure 8A shows electronic unit 320 after being bent out of the x-y plane. Figure 8A demonstrates that, even when subjected to a large bending angle, the electronic unit 320 does not buckle. The bending radius of the electronic unit 320 is approximately 1mm, indicated by the horizontal line extending in from the edge of the circle shape annotation on Figure 8A. As such, the conventional electronic unit 310 exhibits flexibility out of the x-y plane. Similarly, Figures 8B and 8C respectively show the electronic units 310, 210 after being bent out of the x-y plane. Figures 8B and 8C demonstrate that, even when subjected to a large bending angle (approximately 180° in Figures 8B and 8C), the electronic units 210, 310 do not buckle and no kinks are formed. The bending radius of the electronic unit 310 is approximately 5mm, indicated by the horizontal line extending in from the edge of the circle shape annotation on Figure 8B. The bending radius of the electronic unit 210 is approximately 2mm, indicated by the horizontal line extending in from the edge of the circle shape annotation on Figure 8C. As such, the electronic units 210, 310 exhibit high levels of both in-plane flexibility and out-of-plane flexibility. The electronic units 210, 310 therefore exhibit high levels of flexibility in substantially all directions. By forming an electronic unit 10, 110, 210, 310 with a helical substrate 12, 112, the inplane flexibility of the electronic unit may be dramatically improved in comparison to a conventional electronic unit 220, 320, whilst also retaining significant out-of-plane flexibility. For example, a bending radius achievable by an electronic unit 10, 110, 210, 310 having a helical substrate 12, 112 may be substantially equal to or smaller than a cross-sectional diameter of the helical substrate 12, 112 in an unbent state, both for inplane bending and out-of-plane bending. Figure 9 shows a method 400 for producing an electronic unit. The method 400 can be used to form the electronic units 10, 110, 210, 310 of any of Figures 1 to 8. Step 402 of the method 400 comprises applying conductive tracks 14 to a non-conductive substrate. The substrate may be or comprise a length of substrate material, for example, a tape, a strip, a yarn or a thread of substrate material. The conductive tracks 14 may be applied to one or both sides of the substrate. The conductive tracks 14 can be applied to or disposed on the substrate by subtractive manufacturing methods, such as etching. For example, a layer of conductive material can be applied to the substrate and then selectively etched away to form desired conductive tracks 14. Alternatively, conductive tracks 14 may be disposed on the substrate using additive manufacturing methods, for example using a printing method such as screen-printing, dispenser-printing, lamination or another suitable roll-to-roll process. For example, the conductive tracks 14 may be formed from, or comprise, conductive ink which is printed on and / or embedded into the substrate. Alternatively, a length of conductive material (for example, a wire) may be disposed on or adhered to the substrate 12 to form the conductive tracks 14. Step 404 of the method 400 optionally comprises disposing or mounting one or more electronic or electrical components onto the conductive tracks 14, although that is not essential. The electronic components may be conventional electronic components. The electronic components may be disposed on the conductive tracks 14 in any suitable manner. For example, the electronic components may be soldered to the conductive tracks 14 or may be adhered to the conductive tracks using a conductive adhesive (for example, an anisotropic conductive adhesive). Alternatively, the electronic components may be printed onto the conductive tracks 14. Step 406 of the method 400 comprises forming the substrate into a helix to form a helical substrate 12. The substrate may be formed into a helix by wrapping or winding the substrate around a core 116. The core 116 may be substantially cylindrical, having a substantially circular cross-section, although that is not essential. An adhesive may be applied to the core 116 and / or the substrate to adhere the helical substrate 12 to the core 116, although that is not essential. The adhesive may be applied to a surface of the substrate which faces towards the core 116 when the substrate is wrapped around the core 116. Alternatively, the substrate may be wound into a helix separately from the core 116, and the core 116 subsequently disposed into a central region 11 of the helical substrate 12 (the central region 11 extending through or along a longitudinal axis of the helical substrate 12). The core 116 may be pre-formed and disposed into the central region 11. Alternatively, the core 116 may be formed by disposing core material into the central region 11, for example by injection moulding core material into the central region 11. Alternatively, the helical substrate 12 may be used without a core 116 disposed in the central region 11. Step 408 of the method 400 optionally comprises encapsulating the helical substrate 12 (and optionally the core 116, if present) with an encapsulation layer 118. The encapsulation layer 118 may be applied to the helical substrate 12 alone (for example, the core 116 may be disposed into a central region 11 of the helical substrate 12 after the helical substrate 12 is encapsulated), or may be applied to both the helical substrate 12 and core 116 simultaneously (for example, the helical substrate 12 may be formed by winding the substrate around the core 116 prior to encapsulation, or the core 116 may be disposed into a central region 11 of the helical substrate 12 prior to encapsulation). The encapsulation layer 118 may substantially cover or surround at least a part of the helical substrate 12 (and optionally the core 116, if present), for example one or more portions of the helical substrate 12 or substantially an entire length of the helical substrate 12, as described above with respect to the electronic unit 110. Alternatively, the substrate 12 may be encapsulated with the encapsulation layer 118 prior to being wound into a helical shape. In some embodiments, two encapsulation layers 118 may be applied to the helical substrate 12. In such embodiments, the first encapsulation layer may be applied to the substrate 12 before it is formed into a helix and after the conductive tracks (and electronic components, if present) have been applied to the substrate. The second encapsulation layer may be applied to the helical substrate 12 after it has been formed into a helix, optionally around the core 116. The second encapsulation layer 118 may be applied so that it encapsulates the assembled helical structure (including the core, if present). The encapsulation layer 118 may be applied around or over the helical substrate 12 by vacuum forming. Alternatively, the encapsulation layer 118 may be applied by dispensing, dip-coating or spray-coating the helical substrate 12 with an encapsulating material, or by braiding yarn around the helical substrate 12. From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art of garments or textiles incorporating electronic capabilities, and which may be used instead of, or in addition to, features already described herein. Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. The applicant hereby gives notice that new claims may be formulated to such features and / or combinations of such features during the prosecution of the present application or of any further application derived therefrom. For the sake of completeness, it is also stated that the term "comprising" does not exclude other elements or steps, the term "a" or "an" does not exclude a plurality, a single processor or other unit may fulfil the functions of several means recited in the claims and any reference signs in the claims shall not be construed as limiting the scope of the claims. The following clauses (not claims) are statements defining aspects of the invention. 1. An electronic unit for incorporating into a textile to provide the textile with electronic capability, the electronic unit comprising: a non-conductive helical substrate; and one or more conductive tracks disposed on the substrate. 2. The electronic unit of clause 1, wherein the non-conductive helical substrate defines a central region extending through the helical substrate. 3. The electronic unit of clause 2, wherein one or more of the conductive tracks are disposed on a side of the non-conductive helical substrate facing the central region. 4. The electronic unit of clause 3, wherein each of the one or more conductive tracks are disposed on the side of the non-conductive helical substrate facing the central region. 5. The electronic unit of any preceding clause, further comprising one or more electronic components mounted on and connected to one or more of the conductive tracks. 6. The electronic unit of clause 5, wherein the electronic components are or comprise printed flexible components. 7. The electronic unit of any of clauses 2 to 6, further comprising a core extending through or along least a portion of the central region of the non-conductive helical substrate. 8. The electronic unit of clause 7. wherein at least a portion of the helical substrate is disposed on or supported by the core. 9. The electronic unit of any of clause 7 or clause 8, wherein the core is flexible, and optionally wherein the core is compressible and / or stretchable. 10. The electronic unit of any of clauses 7 to 9, wherein the core is, or comprises, foam. 11. The electronic unit of clause 10, wherein the core is or comprises neoprene foam, EPDM foam, or silicone foam. 12. The electronic unit of any of clauses 7 to 9, wherein the core is or comprises a stretchable polymer. 13. The electronic unit of any of clauses 7 to 9, wherein the core is or comprises a textile. 14. The electronic unit of any of clauses 7 to 13, wherein the core is or comprises a substantially cylindrical shape. 15. The electronic unit of any preceding clause, wherein the non-conductive helical substrate is formed from or comprises a flexible material. 16. The electronic unit of clause 15, wherein the non-conductive helical substrate is formed from or comprises a plastic material, and optionally a plastic film material. 17. The electronic unit of clause 16, wherein the non-conductive helical substrate is made from or comprises polyimide or polyethylene terephthalate. 18. The electronic unit of any preceding clause, further comprising an encapsulation layer. 19. The electronic unit of clause 18, wherein the encapsulation layer is made from or comprises a stretchable adhesive, thermoplastic, or braided yarn. 20. The electronic unit of any preceding clause, wherein the conductive tracks are or comprise a conductive ink. 21. A method of forming an electronic unit for incorporating into a textile to provide the textile with electronic capability, the method comprising: disposing one or more conductive tracks onto a non-conductive substrate; and forming the substrate into a helix. 22. The method of clause 21, wherein forming the substrate into a helix comprises winding the substrate around a core. 23. The method of clause 21, further comprising disposing a core into a central region defined by the helix, and optionally injection moulding a core into the central region. 24. The method of clause 22 or of clause 23, further comprising applying an adhesive between the helical substrate and the core. 25. The method of any of clauses 21 to 24, further comprising applying an 5 encapsulation layer around or over the substrate, and optionally applying the encapsulation layer by vacuum forming, dispensing, dipping, spray coating or braiding yarn. 05 08 25

Claims

1. An electronic unit for incorporating into a textile to provide the textile with electronic capability, the electronic unit comprising:5 a non-conductive helical substrate, wherein the non-conductive helical substratedefines a central region extending through the helical substrate;one or more conductive tracks disposed on the substrate, wherein one or more of the conductive tracks are disposed on a side of the non-conductive helical substrate facing the central region;10 a core extending through or along at least a portion of the central region of thenon-conductive helical substrate, wherein the core comprises foam; andone or more electronic components mounted on and connected to one or more of the conductive tracks.15 2. The electronic unit of claim 1, wherein each of the one or more conductive tracksare disposed on the side of the non-conductive helical substrate facing the central region.

3. The electronic unit of any preceding claim, wherein the one or more electronic 20 components are soldered to one or more of the conductive tracks.

4. The electronic unit of claims any of claims 1-3, wherein the electronic components are or comprise printed flexible components.25 5. The electronic unit of any preceding claim, wherein at least a portion of thehelical substrate is disposed on or supported by the core.

6. The electronic unit of any preceding claim, wherein the core is flexible, and optionally wherein the core is compressible and / or stretchable.

307. The electronic unit of any preceding claim, wherein the core is or comprisesneoprene foam, EPDM foam, or silicone foam.

8. The electronic unit of any preceding claim, wherein the core is or comprises a 35 stretchable polymer.05 08 259. The electronic unit of any preceding claim, wherein the core is or comprises a substantially cylindrical shape.5 10. The electronic unit of any preceding claim, wherein the non-conductive helicalsubstrate is formed from or comprises a flexible material.

11. The electronic unit of claim 10, wherein the non-conductive helical substrate is formed from or comprises a plastic material, and optionally a plastic film material.1012. The electronic unit of claim 11, wherein the non-conductive helical substrate is made from or comprises polyimide or polyethylene terephthalate.

13. The electronic unit of any preceding claim, further comprising an encapsulation 15 layer.

14. The electronic unit of claim 13, wherein the encapsulation layer is made from or comprises a stretchable adhesive, thermoplastic, or braided yarn.20 15. The electronic unit of any preceding claim, wherein the conductive tracks are orcomprise a conductive ink.

16. A method of forming an electronic unit for incorporating into a textile to provide the textile with electronic capability, the method comprising:25 disposing one or more conductive tracks onto a non-conductive substrate;mounting and connecting one or more electronic components onto the one or more conductive tracks;forming the substrate into a helix, such that one or more of the conductive tracks are disposed on a side of the non-conductive helical substrate facing a central region;30 anddisposing a core into the central region defined by the helix of the non-conductive substrate, wherein the core comprises foam.

17. The method of claim 16, wherein forming the substrate into a helix comprises 35 winding the substrate around the core.

18. The method of claim 16, comprising injection moulding a core into the central region.5 19. The method of claim 17 or of claim 18, further comprising applying an adhesivebetween the helical substrate and the core.

20. The method of any of claims 16 to 19, further comprising applying an encapsulation layer around or over the substrate, and optionally applying the 10 encapsulation layer by vacuum forming, dispensing, dipping, spray coating or braiding yarn.5 08 25

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