GB2588885A

GB2588885A - Planar resonator

Info

Publication number: GB2588885A
Application number: GB1914854.3A
Authority: GB
Inventors: Kunovski Philip
Original assignee: Kymira Ltd
Current assignee: Kymira Ltd
Priority date: 2019-10-14
Filing date: 2019-10-14
Publication date: 2021-05-19
Anticipated expiration: 2039-10-14
Also published as: GB2588885B; GB201914854D0

Abstract

A planar resonator 100, or a method suitable for its manufacture, which is suitable for wireless power transfer, comprises: first and second two-dimensional arrays of conductive elements 102, 104 which are separated by a dielectric material layer 106, wherein each conductive element of the first, or second, array at least partially overlaps with one or more of the conductive elements of the second, or first, array, respectively. The resonator may have a structure where each conductive element of a respective array does not overlap with any of the other elements of that array. A further dielectric material layer may be provided to separate the second array of elements 104 from a third two-dimensional array of conductive elements and where each of the second array conductive elements partially overlaps with one or more of the conductive elements of the third array. A dielectric layer 106 may be substantially planar and the conductive elements 102, 104 may be printed in a substantially square planar array where the elements of one or more arrays may be identical to one another and the dielectric layer and the elements may be made of flexible or rigid material. Each array may be spatially offset from each adjacent array. The resonator may include an encapsulation layer of material and it may be used in a textile of a garment.

Description

PLANAR RESONATOR

FIELD OF THE INVENTION

The present invention relates to a planar resonator for wireless power transfer., and a method of manufacturing a planar resonator for wireless power transfer.

BACKGROUND

Mid-range wireless power transfer (WPT) technologies have gone through a recent technological leap making them worth consideration for integration in future products (for example, wearable devices, garments, device chargers etc.) WPT technologies are becoming more affordable due to growing demand for distributed and small embedded sensors in devices.

Digital consumer health monitoring is gaining momentum in the fields of sports, healthcare, military and space exploration, but such devices are currently powered by cumbersome power sources, such as larger supercapacitors and battery packs. Those solutions are uncomfortable to wear for any extended period of time. Carrying battery packs and power supplies to monitor the health of an individual means that significant advances in sensor design and lower power electronics are reduced to marginal gains due to an overshadowing worry of battery life.

For centuries, near-field wireless power transmission has been constrained to short distances as it was thought that efficient magnetic induction was not possible over larger distances. Far-field power transfer has been possible for some time, but it suffers from poor efficiency and directionality, and has historically been limited to data transfer applications.

in 2007, mid-range wireless power transfer was shown to be possible using a technique referred to as Strongly Coupled Magnetic Resonance (SCMR), a concept originally theorised by Nikolai Tesla in the early 1890s. Advancements in mid-range power transfer efficiencies have also been made possible using intermittent or 'relay' resonators, any number of which may be placed between the source transmitter and end receiver.

SUMMARY

According to a first aspect, there is provided a planar resonator for wireless power transfer. The planar resonator may comprise a first two-dimensional array of electrically conductive elements. The planar resonator may also comprise a second two-dimensional array of electrically conductive elements. The planar resonator may further comprise a layer of dielectric material disposed between the first array and the second array. Each conductive element of the first array may partially overlap with one or more of the conductive elements of the second array.

The first and/or second array of electrically conductive elements may comprise a plurality of separate electrically conductive elements e.g. two or more.

"Overlapping" is used to mean that, in a direction transverse to the plane of the arrays, one or more electrically conductive element of one of the arrays (e.g. the first array) at least partially overlaps with one or more of the electrically conductive elements of another array (e.g. the second array). There is no overlapping of electrically conductive elements within an array itself. However, when arrays are arranged together e.g. stacked then the electrically conductive elements are arranged such that there is then an overlap in the transverse direction. For example, if the electrically conductive elements of a first array are arranged in a pattern and the electrically conductive elements of a second array are arranged in a pattern that is offset with respect to the electrically conductive elements of the first array, then there will be an overlap.

The overlapping conductive elements of the first array and the second array, together with the layer of dielectric material, may form a network of interconnected inductors and capacitors. The network of inductors and capacitors may allow an AC current Lo flow across the planar resonator. The network of inductors and capacitors may provide the planar resonator with a self-inductance and a self-capacitance, similar to a conventional coil. The overlapping conductive elements of the first array and the second array, together with the layer of dielectric material, may form and/or function as a segmented or discontinuous coil structure. The planar resonator may be electrically equivalent or similar to a conventional coil, but may have a planar structure significantly physically different to a conventional coil. For example, the planar resonator may be substantially flat and thin in comparison to a conventional coil which may be significantly thicker.

Each conductive element of a respective array may not overlap with any of the other conductive elements of that array.

The planar resonator may further comprise a third two-dimensional array of electrically conductive elements. The planar resonator may also comprise a second layer of dielectric material disposed between the second array and the third array.

Each conductive element of the second array may partially overlap with one or more of the conductive elements of the third array.

The planar resonator may comprise a plurality of two-dimensional arrays of electrically conductive elements. The two-dimensional arrays may be arranged in a layered structure (for example, a stack or a sandwich structure). A layer of dielectric material may be disposed between each pair of adjacent two-dimensional arrays in the layered structure. Each conductive element of each two-dimensional array may partially overlap with one or more conductive elements of adjacent two-dimensional arrays in the layered structure. Such a layered structure may comprise two dimensional arrays of electrically conductive elements (C) and layers of dielectric material (D) arranged in a repeating pattern, c.g., C, D, C, D, C... and so on. Different numbers of layers may be included for different resonator applications. For example, a planar resonator having a greater number of layers may exhibit a lower resonant frequency (or frequencies) than a planar resonator having fewer layers. A greater number of layers may increase one or both of a self-capacitance and a self-inductance of the planar resonator, which may result in the planar resonator operating (for example, operating more efficiently) at lower frequencies.

The layer of dielectric material may be substantially planar. The conductive elements may be substantially planar. The conductive elements and/or the layer of dielectric material may have a thickness of between substantially 5 van and 250 p.m, and optionally between substantially 10 p.m and 100 p.m.

At least one of the layers of dielectric material and the conductive elements may be or comprise a flexible material or a flexible region.

The electrically conductive elements of the first and/or second array may be partially or fully arranged in a regular or irregular pattern. The electrically conductive elements of one or more of the arrays may have or comprise a geometric shape and may have or comprise the same geometric shape within each array and/or within a plurality of arrays. The conductive elements may each be or comprise one or more substantially curved, looped or undulating portions or regions. A greater number of curved, looped or undulating portions may increase an inductance of the conductive elements, similar to increasing the number of loops on a conventional helical coil. The conductive elements may be substantially c-shaped, or substantially u-shaped, or substantially spiral shaped, or substantially rectangular. The conductive elements may be substantially circular, substantially arc-shaped or substantially loop shaped. The conductive elements may have a substantially circular, substantially arc-shaped or substantially loop-shaped outer edge or outer perimeter. For example, the conductive elements may each be or comprise a conductive material arranged to follow a substantially circular, arc-shaped or loop-shaped path. The path may form a full circle or closed loop, or may form an arc or open loop. Additionally or alternatively, the conductive elements may be configured to follow a path having one or more curved or looped portions (for example, the conductive elements may be, have or comprise a sinusoidal shape). An outer perimeter of the conductive elements may comprise one or more substantially curved, looped or undulating portions. The conductive elements may have a hierarchical curved structure. For example, the conductive elements may be or comprise a first substantially curved or looped structure (for example, a c-shaped or u-shaped conductive element) upon which a second curved or looped structure is superimposed (for example, a curved, looped, undulating or sinusoidal pattern around a perimeter of the conductive clement). The conductive elements of a respective array may be substantially identical to one another. Alternatively, the conductive elements of a respective array may not be substantially identical to one another. The conductive elements of each array may be substantially identical to the conductive elements of one or more or each of the other arrays. Alternatively, the conductive elements of each array may not be substantially identical to the conductive elements of each of the other arrays. Conductive elements from different arrays which are different sizes and/or different shapes may have areas of overlap which are different in size and/or shape from one another. In turn, the planar resonator may exhibit multiple resonant modes or resonant frequencies.

One or more of the arrays may be or comprise a regular array, for example a square or rectangular array (or other regular shape). Alternatively, one or more of the arrays may be or comprise an irregular array. One or more of the arrays may be substantially identical to one another. Each array may be spatially offset from each adjacent array along an in-plane direction of the planar resonator. Each of the conductive elements of a respective array may partially overlap with one or more of the conductive elements of each adjacent array as a result of the spatial offset. Alternatively, one or more of the arrays may be different from the other arrays. Different arrays of conductive elements may result in areas of overlap between conductive elements which are different in size and/or shape from one another. in turn, the planar resonator may exhibit multiple resonant modes or resonant frequencies.

The planar resonator may comprise a layer of encapsulating material. The layer of encapsulating material may be disposed over at least one of the first array and the second array. The layer of encapsulating material may be disposed over one or both outermost two-dimensional arrays. The encapsulating material may protect the two-dimensional arrays and the layer(s) of dielectric material, for example from water ingress, mechanical damage etc. The encapsulating material may be fluid tight or fluid resistant. The encapsulating material may be strengthening and/or protective. The encapsulating material may be or comprise a vinyl or polyurethane.

A garment may comprise one or more planar resonators of the first aspect.

According to a second aspect, there is provided a wireless power transfer textile. The wireless power transfer textile may comprise a textile substrate. The wireless power transfer textile may also comprise one or more planar resonators of the first aspect disposed on the textile substrate.

According to a third aspect, there is provided a garment comprising the wireless power transfer textile of the second aspect.

According to a fourth aspect, a method of manufacturing a planar resonator for wireless power transfer is provided. The method may comprise disposing a layer of dielectric material between a first two-dimensional array of electrically conductive elements and a second two-dimensional array of electrically conductive elements. Each conductive element of the first array may overlap with one or more of the conductive elements of the second array.

Disposing the layer of dielectric material between the first array and the second array may comprise sequentially disposing the first array, the layer of dielectric material and the second array layer by layer. Sequentially disposing the first array, the layer of dielectric material and the second array may comprise sequentially printing each of the first array, the layer of dielectric material and the second array layer by layer.

The method may comprise sequentially disposing the first array, the layer of dielectric material and the second array onto a substrate. The substrate may be or comprise one of a flexible substrate and a rigid substrate. The substrate may be or comprise a textile substrate.

The method may comprise sequentially disposing the first array, the layer of dielectric material and the second array onto a heat-transfer sheet material. The method may further comprise heat-transferring the first array, the layer of dielectric material and the second array from the heat-transfer sheet material to a substrate. The substrate may be or comprise one of a flexible substrate and a rigid substrate. The substrate may be or comprise a textile substrate.

Disposing the layer of dielectric material between the first array and the second array may comprise disposing the first array on a surface of the layer of dielectric material, and disposing the second array on an opposing surface of the layer of dielectric material. The method may further comprise disposing the first array onto a substrate. The method may comprise adhering the first array to the substrate. The substrate may be or comprise one of a flexible substrate and a rigid substrate. The substrate may be or comprise a textile substrate.

The conductive elements may be substantially planar. The layer of dielectric material may be substantially planar. The conductive elements and/or the layer of dielectric material may have a thickness of between substantially 5 ton and 250 pm, and optionally between substantially 10 p.m and 100 p.m.

The conductive elements may be or comprise a flexible material. The layer of dielectric material may be or comprise a flexible material.

The conductive elements may be or comprise one or more substantially curved, looped or undulating portions or regions. A greater number of curved, looped or undulating portions may increase an inductance of the conductive elements, similar to increasing the number of loops on a conventional helical coil. The conductive elements may comprise a region that is or may be substantially c-shaped, or substantially u-shaped, or substantially spiral shaped, or substantially rectangular, or substantially loop shaped. The conductive elements may comprise a region that is or may be substantially circular, substantially arc-shaped or substantially loop shaped. The conductive elements may have a substantially circular, substantially arc-shaped or substantially loop-shaped outer edge or outer perimeter. For example, the conductive elements may each be or comprise a conductive material arranged to follow a substantially circular, arc-shaped or loop-shaped path. The path may form a full circle or closed loop, or may form an arc or open loop. Additionally or alternatively, the conductive elements may be configured to follow a path having one or more curved or looped portions (for example, the conductive elements may be, have or comprise a sinusoidal shape). An outer perimeter of the conductive elements may comprise one or more substantially curved, looped or undulating portions. The conductive elements may have a hierarchical curved structure. For example, the conductive elements may be or comprise a first substantially curved or looped structure (for example, a c-shaped or u-shaped conductive element) upon which a second curved or looped structure is superimposed (for example, a curved, looped, undulating or sinusoidal pattern around a perimeter of the conductive element). The conductive elements of a respective array may be substantially identical to one another. The conductive elements of each array may be substantially identical to the conductive elements of the other arrays. Alternatively, the conductive elements of each array may not be substantially identical to the conductive elements of each of the other arrays.

Conductive elements from different arrays which are different sizes and/or different shapes may have areas of overlap which are different in size and/or shape from one another. In turn, the planar resonator may exhibit multiple resonant modes or resonant frequencies One or more of the arrays may be or comprise a regular array, for example a square or rectangular array (or other regular shape). Alternatively, one or more of the arrays may be or comprise an irregular array. One or more of the arrays may be substantially identical to one another. Each array may be spatially offset from each adjacent array along an in-plane direction of the planar resonator. Each of the conductive elements of a respective array may partially overlap with one or more of the conductive elements of each adjacent array as a result of the spatial offset. Alternatively, one or more of the arrays may be different from the other arrays. Different arrays of conductive elements may result in areas of overlap between conductive elements which are different in size and/or shape from one another. in turn, the planar resonator may exhibit multiple resonant modes or resonant frequencies.

The method may further comprise disposing a layer of encapsulating material over at least one of the first array and the second array. The layer of encapsulating material may be disposed over one or both outermost two-dimensional arrays. The encapsulating material may protect the two-dimensional arrays and the layer(s) of dielectric material, for example from water ingress, mechanical damage etc. The encapsulating material may be or comprise a vinyl or polyurethane.

Aspects and embodiments of the invention advantageously provide for the use of planar resonators in situations and applications where conventional e.g. coil resonators may not be appropriate. For example, incorporating a conventional coil resonator into a fabric or garment may be difficult and undesirable since the coil imparts a thickness to the resonator. By contrast, the resonator of aspects and embodiments of the invention is much thinner and may, in some embodiments, be flexible. Resonators manufactured according to method aspects and embodiments may also incorporate techniques such as printing of electrically conductive components which again is beneficial for use e.g. in fabrics and garments as they can flex and bend as the fabric/garment flexes and bends. Such manufacturing methods arc also simple and inexpensive.

It will also be appreciated that aspects and embodiments of the invention, through the ability to customise the conductive elements within an array and within different arrays, and to choose the number of arrays, provides an ability to tailor the inductance and/or capacitance as needed for particular applications. Aspects and embodiments of the invention therefore provide an improved level of control and customisability over conventional coil resonators. Aspects and embodiments of the invention can of course still be utilised for providing/manufacturing larger resonators e.g built up with thicker or more layers if a larger resonator is needed.

Features which are described in the context of separate aspects and embodiments of the invention may be used together and/or be interchangeable wherever possible. Similarly; where features arc, for brevity, described in the context of a single embodiment, those features may also be provided separately or in any suitable sub-combination. Features described in connection with the apparatus of the first aspect, the second aspect or the third aspect may have corresponding features definable with respect to the method of the fourth aspect, and these embodiments are specifically envisaged.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference to the accompanying drawings in which: FIG. 1 shows a plan view of an embodiment of a planar resonator in accordance with the invention; FIG. 2 shows a network of inductors and capacitors approximated by the planar resonator shown in FIG. 1; FIG. 3 shows a colour map indicating the strength of an electric field in an embodiment of a planar resonator in accordance with the invention when driven (either by inductance or by direct electrical input); FIG. 4A shows a magnetic field generated by the planar resonator shown in FIG. 3 when driven (either by inductance or by direct electrical input); FIG. 4B shows a magnetic field generated by a conventional helical coil; FIGs SA, 5B, 5C and SD show embodiments of planar resonators in accordance with the invention having different shapes of electrically conductive elements; -Ms. SE to ST show embodiments of planar resonators in accordance with the invention having different shapes or geometries, and a frequency response of some of those planar resonators; FIG. 6 shows an embodiment of a planar resonator in accordance with the invention, having three stacked arrays of electrically conductive elements separated from one another by layers of dielectric material; FIGs. 7A, 7B and 7C show embodiments of planar resonators in accordance with the invention illustrating how the planar resonator structure can be scaled to different sizes; FIGs. 8A and 8B show conventional four-coil wireless power transfer architectures; FIGs. 8C and 8D show embodiments of planar resonators in accordance with the invention incorporated into four-coil wireless power transfer architectures; and FIGs. 8E and 8F show wireless power transfer between embodiments of planar resonators in accordance with the invention.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

Figure 1 shows an embodiment of a planar resonator 100 in accordance with the invention. The planar resonator 100 comprises a first two-dimensional array 102 of electrically conductive elements 102a (shown in solid line). The planar resonator 100 also comprises a second two-dimensional array 104 of electrically conductive elements 104a (shown in dotted line). A layer of dielectric material 106 is disposed between the first array 102 and the second array 104. In the embodiment shown, in a direction transverse to the plane of the first and second arrays 102, 104, each conductive element 102a of the first array 102 partially overlaps with one or more of the conductive elements 104a of the second array 104.

The structure of the planar resonator 100 enables the planar resonator 100 to behave as or approximate a conventional coil for wireless power transfer purposes. A conventional coil comprises a continuous length of electrically conductive wire wound into a shape, typically a helical shape or a spiral shape. The wireless power transfer properties of a conventional coil are governed by the self-inductance and self-capacitance of the coil.

The overlapping conductive elements 102a, 104a of the first array 102 and the second array 104, together with the layer of dielectric material 106, form a network of interconnected inductors and capacitors (depicted in Figure 2) which allow an AC current to flow across the planar resonator 100. This provides the planar resonator 100 with a self-inductance and a self-capacitance, similar to a conventional coil. Therefore, the conductive elements 102a, 104a and the layer of dielectric material 106 of the planar resonator 100 together form a segmented or discontinuous coil structure.

The planar resonator 100 is therefore electrically equivalent to a conventional coil, but has a significantly different physical arrangement. The electrical behaviour of the planar resonator 100 is further depicted in Figures 3 and 4A. Figure 3 shows a map indicating the strength of the electric field (wherein the dark areas "MAX' are indicative of a maximum electric field, and those on the extreme periphery and corners "MIN" are indicative of a minimum electric field generated in the layer of dielectric material 106 between the conductive elements 102a, 104a (whether by inductance or by direct electrical input to the planar resonator 100)), demonstrating the self-capacitance of the planar resonator 100. Figure 4A shows the magnetic field generated by the planar resonator 100 when driven by a direct electrical input. Figure 4B shows the magnetic field generated by a typical helical coil when driven by a direct electrical input. A comparison between the magnetic fields depicted in Figures 4A and 4B illustrates that the magnetic fields produced by the planar resonator 100 and the typical helical coil are very similar in shape and structure. Figures 4A and 4B therefore show how the planar resonator 100 can behave as or approximate a conventional coil for wireless power transfer purposes. As such, the planar resonator provides the same/similar electrical properties as a conventional coil, but the planar nature and/or the structure makes it more appropriate and facilitates use in a variety of applications including incorporation into garments.

Whilst only two conductive dements 102a, 104a for each of the first array 102 and the second array 104 are depicted in Figure 1, the open capacitors shown in Figure 2 indicate that the pattern of overlapping conductive elements 102a, 104a can continue to repeat indefinitely, in both the x-direction and the y-direction (for example, only limited by the size of the layer of dielectric material 106 used, as shown in Figures 3 and 4A) In the embodiment shown in Figure 1, the conductive elements 102a, 104a of both the first array 102 and the second array 104 are each substantially curved, c-shaped, u-shaped or horseshoe-shaped (which will generally be referred to a c-shaped throughout). The c-shaped conductive elements 102a, 104a each have an open end portion 102b, 104b, a body portion 102c, 104c opposite the open end portion 102b, 104b, and arm portions 102d, 104d. The conductive elements 1 0 2a of the first array 102 are arranged such that open end portions 102b of each conductive element 102a face in a common direction. Similarly, the conductive elements 104a of the second array 104 arc arranged such that open end portions 104b of each conductive clement 104a face in a common direction. However, the common direction of the conductive elements 102a of the first array 102 is opposite or antiparallel to the common direction of the conductive elements 104a of the second array 104. It can be seen from Figure I that each respective portion (open end portion 102b, body portion 102c and two arm portions 102d) of a conductive element 102a in the first array 102 is arranged to overlap with a corresponding portion of a different conductive element 104a in the second array 104. In the embodiment shown, for example, the conductive elements 102a, 104a of the first array 102 and the second array 102 are arranged such that for each conductive element 102a: the open end portion 102b is configured Lo overlap with the open end portion 104b of a first conductive element 104a; the body portion 102c is configured to overlap with the body portion 104c of a second conductive element 104a; one arm portion 102d is configured to overlap with an arm portion 104d of a third conductive element 104a; and the other arm portion 102d is configured to overlap with an arm portion 104d of a fourth conductive element 104a, thereby I3 providing an interconnected network of inductors and capacitors which provide the desired electrical properties of the planar resonator 100.

The self-inductance of the planar resonator 100 is determined by the shape of the conductive elements 102a, 104a. The self-capacitance of the planar resonator 100 is determined by the areas of overlap of the conductive elements 102a, 104a. As can be seen from the overlapping c-shaped conductive elements 102a, 104a shown in Figure 1, the different overlapping portions will provide different capacitance values due to different areas of overlap. The non-overlapping portions of each conductive element 102a, 104a also have different shapes as a result, resulting in different inductance values. The different inductance values and capacitance values may result in a plurality of different current loops throughout the planar resonator. The effect of that is that it enables the planar resonator to support multiple resonant modes or resonant frequencies for wireless power transfer, unlike a conventional coil resonator. The same is true for planar resonators having arrays of conductive elements of a different shape and/or arrangement (discussed further below) which have different areas of overlap between conductive elements.

Different resonant modes or resonant frequencies of the planar resonator may be used to wirelessly transfer power at different amplitudes. For example, the planar resonator could wirelessly transfer power at a certain frequency or bandwidth having a larger signal amplitude, and wirelessly transfer data at another frequency or bandwidth having a smaller amplitude (wirelessly transferring data rather than power can be achieved using a smaller signal amplitude).

The frequency response (e.g., a fundamental resonant frequency, or resonant modes or resonant frequencies) of the planar resonator 100 may be tailored or altered by varying one or more parameters of the planar resonator 100. For example, the frequency response of the planar resonator may be tailored by varying one or more of: a size of the individual conductive elements 102a, 104a in the planar resonator 100; a spacing of the conductive dements 102a, 104a relative to one another (which will alter the respective inductance values and capacitance values of the interconnected network of inductors and capacitors by changing the areas of overlap between conductive elements 102a, 104a); a number of conductive dements 102a, 104a in the planar resonator 100, or equivalently an overall size of the planar resonator 100 (a larger planar resonator 100 having a greater number of conductive elements 102a, 104a will have a lower fundamental resonant frequency); a shape of the conductive elements 102a, 104a (which will after the respective inductance values and capacitance values of the interconnected network of inductors and capacitors, and discussed further below); and a thickness of the layer of dielectric material 106 and/or the conductive elements 102a, 104a (for example, a thickness of each layer 106 or array 102, 104 may be between 5 gm and 250 gm, and optionally between 10 gm and 100 gm).

The above illustrates how overlapping regular arrays of conductive elements (for example, a periodic repeating pattern of conductive elements in respect of both spatial arrangement of the conductive elements, and a size and/or shape of the conductive elements) separated by a layer of dielectric material can be used to provide a planar resonator, the frequency response of which can be tightly controlled or tailored by adjusting the parameters of the repeating pattern. The control of the frequency response of such planar resonators is highly predictable, and so planar resonators can be produced to suit a wide variety of applications requiring different frequency responses.

in the embodiments described above, the conductive elements within each array, and within different arrays, are substantially identical to one another in size, shape and spatial separation from one another. However, a regular array of conductive elements may alternatively comprise conductive elements having two or more sizes and/or shapes of conductive elements in a repeating pattern, rather than substantially identical conductive dements. Similarly, rather than two or more substantially identical regular arrays, a planar resonator may alternatively comprise two ore more different regular arrays. in another alternative, a planar resonator may comprise one or more irregular arrays of conductive elements (for example, arrays not having a periodic repeating pattern of conductive elements in respect of at least one of spatial arrangement of the conductive elements and a size and/or shape of the conductive elements themselves). The one or more irregular arrays may be substantially identical to one another, or may be different from one another. Such alternative arrays of conductive elements, separated by a layer of dielectric material may also provide a planar resonator configured to behave as or approximate a conventional coil. Such arrangements can still provide planar resonators in which conductive dements of one array overlap with one or more conductive elements of another array (to provide an interconnected network of inductors and capacitors). A frequency response for a planar resonator comprising one or more irregular arrays may be determined by iteratively altering one or more regular arrays (for example, using simulation software) and determining a frequency response of the altered planar resonator with each iteration until a desired frequency response is achieved. Such approaches are utilised, for example, in antenna design for antennas having or requiring a nonstandard shape (by iteratively altering a known or standard shape).

Figures 5A, 5B, 5C and 5D respectively show planar resonators having different shapes of conductive elements to those shown for the planar resonator 100 discussed above. In the embodiments shown in Figures 5A, 5B and 5C, the conductive elements are each spiral shaped. The spiral shaped conductive elements may be thought of as a planar strip of conductive material arranged into a spiral shape. The width of the planar strip may dictate how tightly the spiral shape can be wound. For example, the width of the planar strip is narrow in Figure 5A, leading to a planar resonator 200 having narrow, tightly wound spiral shaped conductive elements 202a, 204a (e.g., the outer shape of the conductive elements 202a, 204a closely resembling a circular shape due to the relatively lower increase in overall width of the spiral with each additional turn), separated by a layer of dielectric material 206. in contrast, the width of the planar strip is much greater in Figure 5B, leading to a planar resonator 200 having wider, more loosely wound spiral shaped conductive elements 302a, 304a (the outer shape of the conductive elements 302a, 304a not resembling a circular shape due to the relatively higher increase in overall width of the spiral with each additional turn), separated by a layer of dielectric material 306. Figure 5C shows an intermediate planar strip width, resulting in a planar resonator 400 having spiral shaped conductive elements 402a, 404a having an intermediate winding tightness, separated by a layer of dielectric material 406.

IL will be appreciated that the winding tightness of the spiral shaped conductive elements (e.g., the width of the planar strip used to produce the spiral shape) will influence the inductance values and capacitance values across the planar resonator, altering the resonant frequency (or resonant frequencies) of the planar resonator. It can be seen from Figure 5A that the tightly wound spiral shape of the conductive elements 202a, 204a results in a more 'symmetric' arrangement of the conductive elements 202a, 204a. In this case 'symmetric' refers to the similarity (e.g., in shape and/or size) between the various areas of overlap between conductive elements 202a, 204a. In the embodiment shown in Figure SA, the areas of overlap between the conductive elements 202a, 204a are all substantially similar to one another because of the relative circularity of the spiral shapes. The areas of overlap will therefore each have similar capacitances, and the non-overlapping portions of each conductive element 302a, 304a will have similar inductances. In contrast, the embodiment shown in Figure 5B shows conductive elements 304a, 204b having areas of overlap which are different depending on which part of the spiral shape is overlapping with another conductive element 302a, 304a (because of the relative non-circularity of the spiral shapes), introducing a less 'symmetric' or 'non-symmetric' arrangement of the conductive elements 302a, 304a. The different areas of overlap will therefore each have different capacitances, and the non-overlapping portions of each conductive element 302a, 304a will have different inductances. Figures SA, 5B and SC illustrate how the frequency response and behaviour of the planar resonators 200, 300, 400 can be altered or controlled by using a different shape of conductive elements. A less symmetric' or 'non-symmetric' arrangement of the conductive elements 302a, 304a (for example, having areas of overlap of different sizes and/or shapes between conductive elements in different arrays) enables the planar resonator 300 to support multiple resonant modes or resonant frequencies, as described above.

Figure 5D shows a planar resonator 500 having substantially spiral shaped conductive elements 502a, 504a with an outer end portion 502e, 504e of the conductive clement 502a, 504a extending away from the main body 502f, 504f of the spiral rather than continuing to wind around the main body 502f, 504f of the spiral shape. The outer end portion 502e of a conductive element 502a overlaps with the outer end portion 504e of a conductive element 504a, as shown in Figure 5D. The main body 502f of the spiral shape of the conductive element 502a overlaps with the main body 504f of the spiral shape of at least one conductive element 504a. The arrangement shown in Figure SD means that each conductive element 502a is arranged to overlap with at most three conductive elements 504a, rather than with four conductive elements 204a, 304a, 404a as shown in Figures SA, 5B and SC respectively. Figure 5D further illustrates a 'non-symmetric' arrangement of conductive elements 502a, 504a resulting in areas of overlap between conductive elements having a different shape and/or size. As a result, the planar resonator 500 is likely to support multiple resonant modes or resonant frequencies.

The frequency response of planar resonators having different geometries (e.g., conductive element shape, conductive element spacing, area of overlap between conductive elements etc.) is also illustrated in the spectra shown in Figures SE to SL.

Figures SE and SF show partial frequency responses for a planar resonator as shown in Figure SG (a 6x6 arrangement of C-shaped elements, similar to that shown in Figure 3). Figure SE shows the lowest three resonant frequencies of the planar resonator, at approximately 78 MHz, 83 MI-lz and 89 MHz. Figure 5F shows the highest three resonant frequencies of the planar resonator, at approximately 114 MHz, 123 MHz and MHz.

Figures 5H and Si show a frequency response for a planar resonator having an arrangement as shown in Figure 5.1 (an 8x8 arrangement of c-shaped elements). Figure 5H shows a frequency response for a planar resonator in which a thickness of the conductive elements of both the first array and the second array is 144 min, and a thickness of the layer of dielectric material is 144 um (the 'thick-layer' 8x8 planar resonator). Figure 51 shows a frequency response for a planar resonator in which a thickness of the conductive elements of both the first array and the second array is 24 [an, and a thickness of the layer of dielectric material is 24 um (the 'thin-layer' 8x8 planar resonator). Increased thickness of the conductive elements and layer of dielectric material in the thick-layer planar resonator significantly increases the fundamental frequency and the subsequent resonant modes of the planar resonator, as illustrated in the different frequency responses shown in Figures 5F1 and 51. The lowest frequency resonant modes exhibited by the thick-layer planar resonator are between substantially 95 MHz and 105 MHz. in contrast, the lowest frequency resonant modes exhibited by the thin-layer planar resonator are between substantially 70 MHz and 80 MHz. Additionally, the increase in self-capacitance changes a shape of the resonant modes. In particular, the thin-layer planar resonator exhibits resonant modes having extended tails on the left-hand side of the peaks.

Figure 5K shows a frequency response for a planar resonator having an arrangement as shown in Figure SL (a 6x6 arrangement of o-shaped elements). Compared to the frequency response shown for a 6x6 arrangement of c-shaped elements, the strongest resonant modes have a much higher frequency, for example approximately 200 MHz, 210 MHz, 245 MHz and 275 MHz (as compared to < 125 MHz). A shape of the resonant modes is also more symmetrical than, for example, the resonant modes shown in Figures 5E, 5F, 5H and 51. Additionally, the resonant modes shown in Figure 5K are in general more clearly separated from one another (for example have greater frequency differences between adjacent resonant modes).

Figures 5E to 5L clearly demonstrate how the frequency response of a planar resonator can be tailored in one or more ways. For example, different thicknesses of the conductive elements and/or the layer of dielectric material may be used. Different shaped conductive elements may also be employed in the planar resonator, or a different number of conductive elements may be used.

Further examples of shapes of conductive elements that may be used in planar resonators are shown in Figures 51\4 to 5Q. The conductive elements of Figures 5M to 5Q and 5R show conductive elements having a hierarchical curved structure, with a first curved structure (for example, a substantially circular shape or loop-shape) around the perimeter of which is a second curved structure (for example, a substantially curved, looped or undulating pattern). Figures SM to SP and SR depict conductive elements formed from, for example, conductive material (such as a wire) arranged in a regular pattern around an overall loop-shape or circular shape. In Figure 5M, the regular pattern is a zig-zag pattern. In Figure 5N, the regular pattern is a spiral pattern. In Figure 50, the pattern is a series or plurality of arc-shapes joined end to end. In Figure 5P, the pattern is or approximates a sine wave.

In Figure SR, the pattern is or approximates a sine wave around the perimeter of a substantially c-shaped or loop-shaped conductive element. Figure 5S illustrates how the conductive elements shown in Figure SR could be arranged to overlap with one another in a planar resonator. Figure ST shows a frequency response for a planar resonator having an arrangement as shown in Figure 5S.

Alternatively, the pattern may be an irregular pattern (for example, the pattern may not repeat around the loop-shape or circular shape). In further alternatives, the loop-shape or circular shape may not be a closed loop or full circle as shown in Figures SM to SP. instead, the loop-shape may be an open loop or may be an arc, for example being partly or substantially loop-shaped or circular without the ends of the loop or arc meeting or joining with one another. Figure 5Q shows a further alternative shape for a conductive element to be used in a planar resonator, comprising a substantially sine wave shape (for example, in a substantially linear direction rather than around a loop-shape or circular shape as shown in Figure 5P).

Figure 6 shows an embodiment of a planar resonator 600 in accordance with the invention. The planar resonator 600 comprises a first two-dimensional array 602 of electrically conductive elements 602a. The planar resonator 600 also comprises a second two-dimensional array 604 of electrically conductive elements 604a. A layer of dielectric material 606 is disposed between the first array 602 and the second array 604. The planar resonator 600 also comprises a third two-dimensional array 608 of electrically conductive elements 608a. A layer of dielectric material 606' is disposed between the second array 604 and the third array 608. The planar resonator 600 therefore comprises a stack of two-dimensional arrays of electrically conductive elements, adjacent arrays separated by a layer of dielectric material. In the embodiment shown, each of the conductive elements of each array partially overlaps with one or more of the conductive dements of each adjacent array to form an interconnected network of inductors and capacitors, substantially as described above.

In the embodiment shown in Figure 6, the two-dimensional arrays are substantially identical to one another. In such embodiments, whilst a shape of the frequency response of the planar resonator 600 is governed or controlled by the arrangement of each of the two-dimensional arrays 602, 604, 608 of conductive elements, the number of repeated layers in the planar resonator 600 shifts the frequency response of the planar resonator 600 either up or down in frequency. A greater number of layers may increase one or both of a self-capacitance and a self-inductance of the planar resonator 600. As a result, the planar resonator 600 is likely to exhibit a lower resonant frequency or resonant frequencies with a greater number of layers (for example, the number of resonant modes may be dependent on the number of different sizes and/or shapes of areas of overlap between conductive elements in adjacent arrays). In this way, the arrays 602, 604, 608 can be designed, for example, to have two or more resonant modes each separated by a frequency range. The number of layers of the arrays 602, 604, 608 in the planar resonator 600 can then be selected to shift the resonant frequencies as desired in order to target one or more specific frequencies of operation. This may be useful, for example, to operate at different power transmission standards. For example, the ISM band has discrete frequency allocated as follows: 6.765 MHz to 6.795 MHz; 13.553 MHz to 13.567 MHz; 26.957 MHz to 27.283 MHz; 40.66 MHz to 40.70 MHz, and so on. A planar resonator could be designed as described above to exhibit different resonant modes centred, for example, around the frequency bands listed above (or other frequency bands of choice).

Planar resonators as described above are particularly suited to use across a wide range of operating frequencies due to both the inherent scalability of the structure of the planar resonators (the planar layered structure can be extended across a surface as large as required to provide a desired frequency response), and the variation of the respective parameters of the planar resonators (for example, one or more of a size, shape, number and spatial arrangement of the conductive elements, a thickness of the layer(s) of dielectric material). Figures 7A, 7B and 7C illustrate how the structure of a planar resonator 100 (but equally planar resonators 200, 300, 400, 500 or 600 described above) can be scaled up or extended across different sizes of surface.

Planar resonators as described above may be used to directly transmit or receive power wirelessly. Alternatively, a planar resonator as described above may be used in place of an intermediary resonant coil, for example in a four-coil wireless power transfer architecture. Figure SA shows a typical four-coil architecture for wireless power transfer employing helical coils. Figure 8A shows an architecture having a source coil 710, a transmitter resonant coil 712, a receiver resonant coil 714, and a load coil 716. Figure 8B shows another typical four-coil architecture for wireless power transfer, this time employing co-planar source coil 710 and transmitter resonant coil 712, and coplanar receiver resonant coil 714 and load coil 716. Figure 8C shows use of a planar resonator 100 in place of the receiver resonant coil 714 in a four-coil wireless power transfer architecture (multiple load coils 716 are shown in Figure 8C). Figure 8D shows use of a planar resonator 100 in place of both the transmitter resonant coil 712 and the receiver resonant coil 714 in a four-coil wireless power transfer architecture (multiple load coils 716 are shown in Figure 8D). Figures SE and SF respectively show wireless power transfer between adjacent planar resonators 100. One of the planar resonators 100 is driven electrically to produce a magnetic field which in turn induces an electrical output in the other planar resonator 100. In the embodiments shown, the planar resonators 100 transfer power wirelessly using strongly coupled magnetic resonance (SCMR), as indicated by the lines of magnetic flux between the adjacent resonators 100. For Figures 8C to 8F, where reference is made to planar resonator 100 it will be appreciated that planar resonators 200, 300, 400, 500 or 600 could be used instead.

A method of manufacturing a planar resonator 100 is now described. Although reference is made to planar resonator 100, it will be appreciated that planar resonators 200, 300, 400, 500 or 600 could be manufactured according to the method instead. The method comprises disposing a layer of dielectric material 106 between a first two-dimensional array 102 of electrically conductive elements 102a and a second two-dimensional array 104 of electrically conductive elements 104a, wherein one or more or each conductive element 102a of the first array 102 overlaps with one or more of the conductive elements 104a of the second array 104.

in some embodiments, disposing the layer of dielectric material 106 between the first array 102 and the second array 104 comprises sequentially disposing the first array 102, the layer of dielectric material 106 and the second array 104 layer by layer. In a particular example, the separate layers (e.g., the first array 102, the layer of dielectric material 106 and the second array 104) of the planar resonator 100 are printed layer by layer (for example, using screen printing). Each of the first array 102 and the second array 104 is formed by printing a conductive material (for example, a conductive ink, such as a silver ink or a copper ink) into a desired arrangement, i.e., an array of discrete conductive elements 102a, 104a. The layer of dielectric material 106 is formed by printing a dielectric material (for example, a dielectric ink, or a polymeric or rubber material such as vinyl, polyethylene terephthalate (PET) or polyurethane) as a continuous layer over the first array 102. In some embodiments, one or both of the conductive material and the dielectric material is flexible. The term 'flexible' as used here means that the conductive material and/or the dielectric material easily conform to a different shape by elastically deforming in response to an applied force. A thickness of Lhe layer of dielectric material 106 and the conductive elements 102a, 104a is controllable using a printing process (for example, a thickness of each layer may be between 5 pm and 250 um, and optionally between 10 pm and 100 pm). In some cases, a material which does not normally exhibit 'flexible' behaviour may exhibit 'flexible' behaviour when present in a sufficiently thin layer (for example, at the layer thicknesses described above).

In some embodiments, the separate layers are disposed or printed sequentially directly onto a substrate. The substrate may be flexible (for example, a flexible textile material such as a sheet of fabric), or the substrate may be rigid (for example, a flat surface such as a sheet, board or panel, or surface of a wall or table). The substrate with the planar resonator 100 disposed or printed on it may subsequently be affixed to a different surface. For example, a sheet, or board or panel with the planar resonator 100 printed on it may be affixed to a flat surface such as a wall. Alternatively, if the substrate is flexible, the substrate with the planar resonator 100 disposed or printed on it may be affixed to or located on a flat surface (for example a wall) or a non-flat surface (for example, wrapped around a post or pole).

In alternative embodiments, the separate layers are printed sequentially onto a heat-transfer sheet material, instead of directly onto the intended substrate (for example, a flexible textile material). Subsequently, the planar resonator 100 may be heat-transferred as a single entity onto the substrate. The planar resonator 100 is brought into contact with the substrate, and heat transferred to the substrate using the application of heat (and optionally pressure). In other embodiments, each layer is printed onto a heat-transfer sheet material, and individual layers of the planar resonator 100 are heat transferred to the substrate separately to form the planar resonator 100 in situ on the substrate. In some embodiments, an adhesive may be disposed on the substrate prior to heat transferring the planar resonator 100 (or first layer of the planar resonator 100, for example the first array 102) onto the substrate, in order to improve adhesion of the planar resonator 100 to the substrate. The adhesive may be a heat-activatable adhesive which is activated during the application of heat whilst the planar resonator 100 is heat transferred to the substrate. For a textile substrate, the adhesive may be a heat-activatable fabric adhesive. It will be appreciated that the printing method described above can be applied to produce or manufacture planar resonators having more than two two-dimensional arrays of conductive elements, each array separated by a layer of dielectric material.

in some embodiments, the planar resonator 100 comprises (for example, is coated in) an encapsulating material (for example, vinyl or polyurethane). The encapsulating material may be waterproof to protect the planar resonator 100 from fluid ingress and associated damage, for example from sweat, washing fluids (e.g., water, detergent) etc. The encapsulating material may also protect the planar resonator 100 from mechanical damage such as impact. The encapsulating material may be disposed over the planar resonator once the planar resonator 100 has been applied to the substrate, or prior to the application of the planar resonator 100 to the substrate (for example, the encapsulating material may be one of the layers heat transferred onto the substrate as part of a single entity planar resonator 100).

Printing (for example, screen printing) is a well-established manufacturing technique used to produce thin, substantially planar layers of material. Printing is a simple, highly scalable approach for producing planar resonators for wireless power transfer at a range of different sizes. In particular, the application of a planar resonator to a flexible textile material using printing allows the simple incorporation of wireless power transfer capabilities into wearable garments (for example, t-shirts, shirts, vests, shorts, trousers, jumpers, hoodies, sweatshirts etc.) A planar resonator 100 comprising a flexible conductive material and/or a flexible dielectric material means that the planar resonator can conform to a wearer's physiology once incorporated into the garment, whilst still providing wireless power transfer capabilities. Such garments may also incorporate electrically powered sensors configured to monitor one or more physiological parameters of the wearer (for example, in garments for sportspeople). Typically, garments comprising sensors require a dedicated power source (for example, a battery back) to be included in the garment. Such dedicated power sources can often be bulky, heavy and uncomfortable for the wearer. By incorporating a planar resonator 100 into the garment, the need for a dedicated power source may be removed or at least reduced. Power can be transferred wirelessly to the garment to power the sensors in the garment, without, for example, impacting on the performance of the person wearing the garment. A battery unit used in a garment incorporating a planar resonator 100 may be smaller (for example, have a smaller capacity) than a typical dedicated power sourcc for such garments, due to the planar resonator 100 being able to wirelessly receive power. The planar resonator 100 may also improve ease of charging of the battery unit in the garment, as no physical connection to the battery unit from an external charging unit may be required. The planar resonator 100 may receive power wirelessly to charge the battery unit. incorporating the planar resonator 100 in a garment may allow the charging area to be spread over a wide surface area without using excess material. Additionally, an increased surface area of the planar resonator 100 may make wireless power transfer more tolerant to misalignment of the source and receiver. Printing also allows planar resonators to be applied to a textile surface to either form at least part of a visually aesthetic design or pattern (for example, using opaque and/or coloured materials), or applied discreetly to a textile surface (for example, using substantially transparent materials).

in other embodiments, the separate layers of the planar resonator 100 may be disposed (either directly onto a substrate, or onto a heat-transfer sheet material) using other application methods such as spray coating, curtain coating, dip coating etc. In some embodiments, different techniques may be used in respect of different layers of the planar resonator 100. In some embodiments, it may be necessary to use a stencil to dispose the discrete conductive elements IO2a, 104a of the first array 102 and the second array 104 respectively. A thickness of each layer in the planar resonator 100 may be between 5 pm and 250 pm, and optionally between 10 nm and 100 nm.

in alternative embodiments, disposing the layer of dielectric material 106 between the first array 102 and the second array 104 comprises disposing the first array 102 on a first surface of a pre-fabricated layer of dielectric material 106, and disposing the second array 104 on a second opposing surface of the layer of dielectric material 106. The pre-fabricated layer of dielectric material 106 may have a thickness of between 5 pm and 250 pm, and optionally between 10 pm and 100 pm. The pre-fabricated layer of dielectric material 106 may be or comprise a polymeric or rubber material such as vinyl, polyethylene terephthalate (PET) or polyurethane. The pre-fabricated layer of dielectric material 106 may be a flexible material, or may be a rigid material (depending on the nature of the substrate the planar resonator 100 is to be incorporated into or attached to). The conductive elements 102a of the first array 102 on the first surface of the layer of dielectric material 106 may comprise employing one of the methods outlined above (for example, printing, spray coating, curtain coating, dip coating etc.) Alternatively, the conductive elements 102a may be prefabricated, and subsequently adhered to the layer of dielectric material 106 (for example, heat transferred onto the layer of dielectric material 106 as described above, or using an adhesive to adhere the conductive elements 102a to the layer of dielectric material 106). The conductive elements 102a, 104a may have a thickness of between 5 pm and 250 gm, and optionally between 10 pm and 100 pm. Once formed, the planar resonator 100 can be disposed as a single entity onto a substrate, for example a flexible substrate such as a textile substrate, or a rigid substrate such as a board or panel or sheet. The planar resonator 100 may be encapsulated in a layer of encapsulating material (for example, vinyl or polyurethane), or a layer of encapsulating material may be disposed over an outer surface of the planar resonator 100. The encapsulating material may be applied to the planar resonator 100 before or after the planar resonator 100 is disposed on the substrate.

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 wireless power transfer, 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. Features of the devices and systems described may be incorporated into/used in corresponding methods. Where features are disclosed in connection with one embodiment of a planar resonator, it should be appreciated that any one or more or all of the same features may be incorporated in other embodiments of planar resonators, instead of or in addition Lo the features described for the particular embodiment. i.e. any and all combinations of features are envisaged, and are envisaged to be interchangeable, replaceable, added or removed.

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.

Claims

CLAIMSA planar resonator for wireless power transfer, the resonator comprising: a first two-dimensional array of electrically conductive elements; a second two-dimensional array of electrically conductive elements; and a layer of dielectric material disposed between the first array and the second array.wherein each conductive clement of the first array partially overlaps with one or more of the conductive elements of the second array. I0
2. The wireless power transfer structure of any of claim 1, wherein each conductive element of a respective array does not overlap with any of the other conductive elements of that array.
3. The planar resonator of claim 1 or of claim 2, further comprising: a third two-dimensional array of electrically conductive elements; and a second layer of dielectric material disposed between the second array and the third array; wherein each conductive element of the second array partially; overlaps with one or more of the conductive elements of the third array.
4. The planar resonator of any preceding claim, wherein the layer of dielectric material is substantially planar, and optionally wherein the conductive elements arc substantially planar.
5. The planar resonator of any preceding claim, wherein at least one of the layer of dielectric material and the conductive elements is or comprises a flexible material.
6. The planar resonator of ally preceding claim, wherein the conductive elements of a respective array are substantially identical to one another.
7 The planar resonator of claim 6, wherein the conductive elements of each array are substantially identical to the conductive elements of each of the other arrays.
8. The planar resonator of any preceding claim, wherein each array is a regular arra
9. The planar resonator of any preceding claim, wherein the arrays are substantially identical to one another.
10. The planar resonator of claim 9, wherein each array is spatially offset from each adjacent array along an in-plane direction of the planar resonator.
11. The planar resonator of claim 10, wherein each of the conductive elements of a respective array partially overlaps with one or more of the conductive elements of each adjacent array as a result of the spatial offset.
12. The planar resonator of any preceding claim, further comprising a layer of encapsulating material over at least one of the first array and the second array.
13. A wireless power transfer textile comprising: a textile substrate; and one or more planar resonators of any of claims 1 to 12 disposed on the textile substrate.
14. A garment comprising the wireless power transfer textile of claim 13.
15. A method of manufacturing a planar resonator for wireless power transfer 25 comprising: disposing a layer of dielectric material between a first two-dimensional array of electrically conductive elements and a second two-dimensional array of electrically conductive elements: wherein each conductive element of the first array overlaps with one or more of the conductive elements of the second array.
16. The method of claim 15, wherein disposing the layer of dielectric material between the first array and the second array comprises: sequentially disposing the first array, the layer of dielectric material and the second array layer by layer.
17. The method of claim 16, wherein sequentially disposing the first array, the layer of dielectric material and the second array comprises sequentially printing each of the first array, the layer of dielectric material and the second array layer by layer. 5
18. The method of claim 16 or of claim 17, further comprising disposing the first array, the layer of dielectric material and the second array onto a substrate, and optionally wherein the substrate is or comprises one of a flexible substrate and a rigid substrate, and further optionally wherein the substrate is or comprises a textile substrate.
19. The method of claim 16 or of claim 17, further comprising disposing the first array, the layer of dielectric material and the second array onto a heat-transfer sheet material.
20. The method of claim 19, further comprising heat-transferring the first array, the layer of dielectric material and the second array from the heat-transfer sheet material to a substrate.
21. The method of claim 15, wherein disposing the layer of dielectric material between the first array and the second array comprises: disposing the first array on a surface of the layer of dielectric material; and disposing the second array on an opposing surface of the layer of dielectric material.
22. The method of claim 21, further comprising disposing the first array onto a substrate, and optionally adhering the first array to the substrate.
23. The method of any preceding method claim, further comprising disposing the first array and the second array such that each conductive element of the first array partially overlaps with one or more of the conductive elements of the second array.
24. The method of any preceding method claim, further comprising disposing each of the first array and the second array such that each conductive element of each respective array does not overlap with any of the other conductive elements in that array.
25. The method of any preceding method claim, wherein: i) the conductive elements are substantially planar; and/or ii) the layer of dielectric material is substantially planar.
26. The method of any preceding method claim, wherein: i) the conductive elements are or comprise a flexible material; and/or ii) the layer of dielectric material is or comprises a flexible material.
27. The method of any preceding method claim, wherein the conductive elements are substantially identical to one another.
28. The method of any preceding method claim, wherein each of the first array and the second array is or comprises a regular array, and optionally is or comprises a square array.
29. The method of any preceding claim, wherein the first array and the second array arc substantially identical to one another.
30. The method of any preceding claim, further comprising disposing a layer of encapsulating material over at least one of the first array and the second array.