Patent Publication Number: US-11664850-B2

Title: Coil and method of making same

Description:
BACKGROUND 
     Coils used in antennas are known. Inductive coupling between coils can be used in wireless power systems. In this approach, a transmitter coil in one device transmits electric power across a short distance to a receiver coil in another device. 
     SUMMARY 
     In some aspects of the present description, an antenna for transfer of information or energy is provided. The antenna includes an electrically conductive magnetically insulative first layer having a width W, a thickness T, and extending longitudinally along a length L of the first layer between first and second longitudinal ends of the first layer, and a magnetically conductive second layer bonded to the first layer along the length of the first layer. The first and second layers are wound to form a plurality of substantially concentric loops. A width and a length of the second layer are substantially co-extensive with the respective width and length of the first layer so as to expose opposing longitudinal edge surfaces of the first layer along the length of the first layer. 
     In some aspects of the present description, a coil including a multilayer film wound to form a plurality of substantially concentric loops is provided. The multilayer film includes a magnetically conductive first layer and a plurality of alternating second and third layers disposed on and bonded to the first layer. The second layers are electrically conductive and magnetically insulative. The third layers are electrically and magnetically insulative. Widths and lengths of the first, second and third layers are substantially co-extensive with each other so that no longitudinal edge surface of a second layer is covered by either a third layer or the first layer. 
     In some aspects of the present description, a coil including a plurality of substantially concentric loops is provided. Each loop includes an edge surface substantially perpendicular to an adjacent loop. The edge surface includes a regular pattern extending along a first direction making an angle θ with a longitudinal direction of the loop. θ varies along the longitudinal direction of the loop. 
     In some aspects of the present description, a coil including a plurality of substantially concentric loops is provided. Each loop includes an edge surface substantially perpendicular to an adjacent loop. The edge surface includes a regular pattern extending substantially laterally across the edge surface. The regular patterns of the edge surfaces of at least a plurality of adjacent loops are substantially aligned with each other. 
     In some aspects of the present description, a coil including a plurality of substantially concentric loops is provided. Each loop includes a plurality of substantially concentric metal layers substantially concentric with at least one soft magnetic layer, such that in a plan view, the coil includes a regular pattern of substantially parallel grooves extending across at least a plurality of adjacent loops in the plurality of substantially concentric loops. 
     In some aspects of the present description, a coil including a plurality of substantially concentric loops is provided. Each loop includes a plurality of substantially concentric alternating metal and first adhesive layers. A second adhesive layer is disposed between and bonding adjacent loops. The second adhesive layer is thicker than the first adhesive layer. 
     In some aspects of the present description, a coil including a plurality of substantially concentric loops is provided. Each loop includes a metal layer. In a plan view, the coil includes a regular pattern extending substantially along a same first direction and across substantially the entire coil. The regular pattern has a first average pitch in a first region of the coil and a different second average pitch in a different second region of the coil. 
     In some aspects of the present description, a coil including a plurality of substantially concentric loops is provided. Each loop includes a metal layer. In a plan view, the coil includes a regular pattern extending substantially along a same first direction and across substantially the entire coil. A Fourier transform of the regular pattern has a peak at a first spatial frequency in a first region of the coil and a peak at a different second spatial frequency in a different second region of the coil. 
     In some aspects of the present description, an antenna for transfer of information or energy is provided. The antenna includes a plurality of substantially concentric loops, each loop including a metal layer, such that in a plan view and in at least one first region of the antenna, the antenna includes a regular optical and topographical pattern along a first direction, and a regular optical, but not topographical, pattern along an orthogonal second direction. 
     In some aspects of the present description, an antenna for transfer of information or energy is provided. The antenna includes an electrically conductive magnetically insulative first layer having opposing major surfaces and opposing edge surfaces connecting the opposing major surfaces and a magnetically conductive second layer disposed on and bonded to the first layer and substantially co-extensive in length and width of the first layer so as to not cover edge surfaces of the first layer. The first and second layers are wound to form a plurality of substantially concentric loops. 
     In some aspects of the present description, a substantially planar coil for transfer of information or energy is provided. The coil includes an electrically conductive magnetically insulative first layer and a magnetically conductive second layer disposed on and bonded to the first layer and substantially co-extensive in length and width of the first layer so as to not cover edge surfaces of the first layer. 
     In some aspects of the present description, a coil including a multilayer film wound to form a plurality of substantially concentric loops is provided. The multilayer film incudes an electrically conductive magnetically insulative first layer, and a magnetically conductive second layer disposed on and bonded to the first layer, such that corresponding edge surfaces of the first and second layers are substantially co-planar. 
     In some aspects of the present description, a coil or antenna including a plurality of loops is provided. Each loop includes at least one electrically conductive layer and at least one other layer. Each loop may include a plurality of electrically conductive layers which may alternate with a plurality of adhesive layers. The at least one other layer may include one or more magnetically conductive and/or magnetically soft layers. In some aspects of the present description, a method of making the coil or antenna is provided. The method includes cutting or slicing through an assembly to provide a separated portion of the assembly that includes the coil or antenna. 
     In some aspects of the present description, an assembly including a rod and a multilayer film wound around a plurality of consecutive turns substantially concentric with the rod is provided. The multilayer film includes a plurality of alternating metal and first adhesive layers, and a magnetically conductive second layer disposed on and bonded to the plurality of alternating metal and first adhesive layers. 
     In some aspects of the present description, a method of making a coil is provided. The method includes providing a rod; providing a multilayer film including an electrically conductive first layer and a magnetically conductive second layer disposed on the first layer; winding the multilayer film around the rod to form an assembly including the rod and a plurality of loops of the multilayer film substantially concentric with the rod; and cutting substantially laterally through the assembly to form a separated portion of the assembly. The separated portion of the assembly includes the coil. The coil includes a plurality of substantially concentric loops of a separated portion the multilayer film. 
     In some aspects of the present description, a method of making a coil is provided. The method includes providing a rod; providing a multilayer film including a plurality of alternating electrically conductive and first adhesive layers and including a second adhesive layer including an outermost major surface of the multilayer film; winding the multilayer film around the rod to form an assembly including the rod and a plurality of loops of the multilayer film substantially concentric with the rod, where each loop is bonded to an adjacent loop through the second adhesive layer; and cutting substantially laterally through the assembly to form a separated portion of the assembly. The separated portion of the assembly includes the coil. The coil includes a plurality of substantially concentric loops of a separated portion the multilayer film. 
     In some aspects of the present description, a method of making a plurality of coils is provided. The method includes providing a rod; providing a multilayer film including an electrically conductive first layer and a second layer disposed on and bonded to the first layer; winding the multilayer film around the rod to form an assembly including the rod and a plurality of loops of the multilayer film substantially concentric with the rod; and slicing substantially laterally through the assembly using a plurality of spaced apart cutting wires to form a plurality of separated portions of the assembly, where each separated portion of the assembly includes a coil in the plurality of coils, and each coil includes a plurality of substantially concentric loops of a separated portion the multilayer film. 
     In some aspects of the present description, a method of making a coil is provided. The method includes providing an assembly comprising a rod and a film wound around a plurality of consecutive turns substantially concentric with the rod, the film comprising an electrically conductive first layer; and slicing substantially laterally through the assembly using at least one cutting wire to form a separated portion of the assembly including the coil, where the coil includes a plurality of substantially concentric loops of a separated portion the film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A- 1 B  are a schematic top plan and side views of a coil, respectively; 
         FIG.  1 C  is a schematic cross-sectional view of a multilayer film of the coil of  FIGS.  1 A- 1 B ; 
         FIG.  1 D  is a schematic top plan view of an assembly including the coil of  FIGS.  1 A- 1 B ; 
         FIG.  2    is a schematic top plan view of a coil; 
         FIGS.  3 A- 3 B  are schematic top plan views of a coil; 
         FIG.  3 C  is a schematic bottom plan view of the coil of  FIGS.  3 A- 3 B ; 
         FIG.  4    is a schematic end view of a multilayer film; 
         FIGS.  5 A- 5 B  are schematic end and side views of a multilayer film, respectively; 
         FIG.  6    is a top view of an assembly including an antenna; 
         FIG.  7 A  is a laser intensity image of a portion of a coil; 
         FIG.  7 B  is a schematic top plan view of a portion of a coil; 
         FIGS.  8 A- 8 B  are a laser intensity image and a topographical map, respectively, of a first region of a coil; 
         FIG.  9    is a topographical map of a portion of the first region of the coil of  FIGS.  8 A- 8 B ; 
         FIG.  10    is a plot of the topography in the first region of the coil of  FIGS.  8 A- 8 B  along a first direction; 
         FIG.  11    is a plot of the topography in the first region of the coil of  FIGS.  8 A- 8 B  along an orthogonal second direction; 
         FIG.  12    is a plot of the magnitude of a two-dimensional Fourier transform of the surface topography in the first region of the coil of  FIGS.  8 A- 8 B ; 
         FIG.  13    is a plot of the magnitude of Fourier transform of the surface topography along the first direction in the first region of the coil of  FIG.  12   ; 
         FIG.  14    is a plot of the magnitude Fourier transform of the surface topography along the second direction in the first region of the coil of  FIG.  12   ; 
         FIGS.  15 A- 15 B  are a laser intensity image and a topographical map, respectively, of a second region of the coil of  FIGS.  8 A- 8 B ; 
         FIG.  16    is a topographical map of a portion of the second region of the coil of  FIGS.  15 A- 15 B ; 
         FIG.  17    is a plot of the topography in the second region of the coil of  FIGS.  15 A- 15 B  along the first direction; 
         FIG.  18    is a plot of the topography in the second region of the coil of  FIGS.  15 A- 15 B  along the second direction; 
         FIG.  19    is a plot of the magnitude of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  15 A- 15 B ; 
         FIG.  20    is a plot of the magnitude Fourier transform of the surface topography in the second region of the coil of  FIGS.  15 A- 15 B  along the first direction; 
         FIG.  21    is a plot of the magnitude Fourier transform of the surface topography in the second region of the coil of  FIGS.  15 A- 15 B  along the second direction. 
         FIGS.  22 A- 22 B  are a laser intensity image and a topographical map, respectively, of a third region of the coil of  FIGS.  8 A- 8 B ; 
         FIG.  23    is a plot of the topography in the third region of the coil of  FIGS.  22 A- 22 B  along the second direction; 
         FIG.  24    is a plot of the magnitude of the Fourier transform of the surface topography in the third region of the coil of  FIGS.  22 A- 22 B ; 
         FIG.  25    is a plot of the magnitude of the Fourier transform of the surface topography in the third region of the coil of  FIGS.  22 A- 22 B  along the first direction; 
         FIG.  26    is a plot of the magnitude of the Fourier transform of the surface topography in the third region of the coil of  FIGS.  22 A- 22 B  along the second direction; 
         FIGS.  27 A- 27 B  are a laser intensity image and a topographical map, respectively, in a fourth region of the coil of  FIGS.  8 A- 8 B ; 
         FIG.  28    is a plot of the topography in the fourth region of the coil of  FIGS.  27 A- 27 B  along the second direction; 
         FIG.  29    is a plot of the magnitude of the Fourier transform of the surface topography in the fourth region of the coil of  FIGS.  27 A- 27 B ; 
         FIG.  30    is a plot of the Fourier transform of the surface topography in the fourth region of the coil of  FIGS.  27 A- 27 B  along the first direction; 
         FIG.  31    is a plot of the magnitude of the Fourier transform of the surface topography in the fourth region of the coil of  FIGS.  27 A- 27 B  along the second direction; 
         FIG.  32    is a top plan view of a coil; 
         FIGS.  33 A- 33 B  are a laser intensity image and a topographical map, respectively, of a comparative coil in a first region; 
         FIG.  34    is a topographical map of a portion of the first region of the coil of  FIGS.  33 A- 33 B ; 
         FIGS.  35 A- 35 B  are plots of the topography in the first region of the coil of  FIGS.  33 A- 33 B  along the first direction at smaller and larger coordinate length scales, respectively; 
         FIG.  36    is a plot of the topography in the first region of the coil of  FIGS.  33 A- 33 B  along the second direction in the first region; 
         FIG.  37    is a plot of the magnitude of the Fourier transform of the surface topography in the first region of the coil of  FIGS.  33 A- 33 B ; 
         FIG.  38    is a plot of the magnitude of the Fourier transform of the surface topography in the first region of the coil of  FIGS.  33 A- 33 B  along the first direction; 
         FIG.  39    is a plot of the magnitude of the Fourier transform of the surface topography in the first region of the coil of  FIGS.  33 A- 33 B  along the second direction; 
         FIGS.  40 A- 40 B  are a laser intensity image and a topographical map, respectively, of the comparative coil of  FIGS.  33 A- 33 B  in the second region; 
         FIG.  41    is a topographical map of a portion of the second region of the coil of  FIGS.  40 A- 40 B ; 
         FIG.  42    is a plot of the topography in the second region of the coil of  FIGS.  40 A- 40 B  along the first direction; 
         FIGS.  43 A- 43 B  are plots of the topography in the second region of the coil of  FIGS.  40 A- 40 B  along the second direction at smaller and larger coordinate length scales, respectively; 
         FIG.  44    is a plot of the magnitude of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  40 A- 40 B ; 
         FIG.  45    is a plot of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  40 A- 40 B  along the first direction; 
         FIG.  46    is a plot of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  40 A- 40 B  along the second direction; 
         FIG.  47    is a top plan view of a coil; 
         FIGS.  48 A- 48 B  are a laser intensity image and a topographical map, respectively, of a comparative coil in a first region of the coil; 
         FIG.  48 C  is a topographical map of a portion of the first region of the coil of  FIGS.  48 A- 48 B ; 
         FIGS.  49 A- 49 B  are plots of topography in the first region of the coil of  FIGS.  48 A- 48 B  along the first direction at smaller and larger coordinate length scales, respectively; 
         FIG.  50    is a plot of the topography in the first region of the coil of  FIGS.  48 A- 48 B  along the second direction; 
         FIG.  51    is a plot of the magnitude of the Fourier transform of the surface topography in the first region of the coil of  FIGS.  48 A- 48 B ; 
         FIG.  52    is a plot of the magnitude of the Fourier transform of the surface topography in the first region of the coil of  FIGS.  48 A- 48 B  along the first direction; 
         FIG.  53    is a plot of the Fourier transform of the surface topography in the first region of the coil of  FIGS.  48 A- 48 B  along the second direction; 
         FIGS.  54 A- 54 B  are a laser intensity image and a topographical map, respectively, of a second region of the coil of  FIGS.  48 A- 48 B ; 
         FIG.  55    is a topographical map of a portion of the second region of the coil of  FIGS.  54 A- 54 B ; 
         FIG.  56    is a plot of the topography in the second region of the coil of  FIGS.  54 A- 54 B  along the first direction; 
         FIGS.  57 A- 57 B  are plots of the topography in the second region of the coil of  FIGS.  54 A- 54 B  along the second direction at smaller and larger coordinate length scales, respectively; 
         FIG.  58    is a plot of the magnitude of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  54 A- 54 B ; 
         FIG.  59    is a plot of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  54 A- 54 B  along the first direction; 
         FIG.  60    is a plot of the Fourier transform of the surface topography in the second region of the coil of  FIGS.  54 A- 54 B  along the second direction; 
         FIG.  61    is a schematic illustration of a multilayer film having an end inserted into a slit in a rod; 
         FIG.  62    is a schematic illustration of a multilayer film being wound around a rod; 
         FIG.  63    is a schematic perspective view of an assembly; 
         FIG.  64    is a schematic illustration of slicing an assembly to make one or more coils; 
         FIG.  65    is a schematic side perspective view of a diamond wire; and 
         FIG.  66    is a schematic side view of a transceiver. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense. 
     Coils described herein may be useful for transfer of information (e.g., digital or analogue data) or energy (e.g., energy for wireless charging). Coils which incorporate layer(s) which are magnetically conductive and/or magnetically soft along with electrically conductive layer(s) have been found to be useful in applications where it is desired to efficiently transfer information or energy. For example, the coil can be useful in the wireless charging of batteries that power electronic devices, such as cellular telephones. The coils can serve to guide magnetic fields during wireless charging, to shield the battery and/or other electronic device components from electromagnetic fields, to reduce eddy currents induced by magnetic fields, and/or to enhance transfer efficiency and/or Q factor of wireless charging systems, for example. The term antenna may be used to refer to a coil that is configured for transfer of information or energy, for example. 
     When higher permeability materials and lower permeability materials are used together (e.g., in a coil), magnetic field lines tend to be more concentrated in the higher permeability material and less concentrated in the low permeability material, so high permeability (e.g., significantly higher than vacuum permeability) materials can be described as magnetically conductive and low permeability (e.g., comparable to vacuum permeability) materials can be described as magnetically insulative. 
     A magnetically conductive material or layer is a material or layer having a relative permeability of at least 2, and a magnetically insulative material or layer is a material or layer having a relative permeability of no more than 1.5. In some embodiments, a magnetically conductive layer has a relative permeability of greater than 2, or greater than 10, or greater than 100. In some embodiments, a magnetically insulative layer has a relative permeability of less than 1.5, or less than 1.4, or less than 1.2, or less than 1.1, or less than 1.05. In some embodiments, a magnetically insulative layer has a relative permeability in a range of 0.99 to 1.05, for example. In some embodiments, a coil includes a plurality of loops where each loop includes a magnetically insulative layer and a magnetically conductive layer. In some embodiments, a relative permeability of the magnetically conductive layer is at least 10 times, or at least 100 times a relative permeability of the magnetically insulative layer. The relative permeability refers to the real part of the complex relative permeability, unless indicated otherwise. 
     A substantially non-magnetic metal is a metal having a relative permeability close to unity (e.g., in a range of 0.98 to 1.1, or 0.99 to 1.05, or 0.99 to 1.01) and not having a stable magnetically ordered phase. A stable phase is a macroscopic phase that is thermodynamically stable at 20° C. in the absence of an applied magnetic field, unless indicated differently. Magnetically ordered phases include ferromagnetic, antiferromagnetic, and ferrimagnetic phases. 
     A soft magnetic material or layer is a material or layer having a coercivity of no more than 1000 A/m. Coercivity is a measure of the magnetic field strength needed to demagnetize a material. Soft magnetic materials or magnetic materials having low coercivity can be described as magnetic materials that are easily demagnetized. In some embodiments, a soft magnetic layer has a coercivity of less than 1000 A/m, or less than 100 A/m, or less than 50 A/m, or less than 20 A/m. 
     In some embodiments, a magnetically conductive layer is soft magnetically. Such a layer may have a relative permeability of greater than 2, or greater than 10, or greater than 100; and a coercivity of less than 1000 A/m, or less than 100 A/m, or less than 50 A/m, or less than 20 A/m. 
     A magnetically conductive layer or a soft magnetic layer may be electrically conductive (e.g., an electrical resistivity of no more than 200 μΩcm) or electrically insulative (e.g., an electrical resistivity of at least 100 Ωm). In some embodiments, an electrically insulative layer (e.g., a magnetically conductive electrically insulative layer or a soft magnetic layer that is electrically insulative) has as an electrical resistivity of greater than 100 Ωm, or greater than 200 Ωm, or greater than 500 Ωm, or greater than 1000 Ωm. In some embodiments, an electrically conductive layer (e.g., a magnetically insulative electrically conducive layer, or a magnetically conductive electrically conducive layer, or a soft magnetic layer that is electrically conductive) has as an electrical resistivity of less than 200 μΩcm, or less than 100 μΩcm, or less than 50 μΩcm, or less than 20 μΩcm, or less than 10 μΩcm. In some embodiments, a magnetically conductive and/or magnetically soft material is electrically conductive. An electrically conductive layer can be formed as a continuous layer of such magnetic materials. An electrically insulative layer can be formed by dispersing particles of such magnetic materials in an electrically insulative binder at concentrations where electrically continuous paths through the layer do not form. At higher concentrations, the layer can become electrically conductive. In some embodiments, a composite layer includes different types of soft magnetic particles where some particles are electrically conductive and other particles are electrically insulative. The resistivity can be adjusted by adjusting the volume fraction of the conductive particles. Electrical resistivity refers to the intrinsic electrical resistivity, unless indicated differently. 
     Magnetic and electric properties (e.g., relative permeability, coercivity, electrical resistivity) refers to the respective property evaluated at low frequencies (e.g., about 1 kHz or less) or evaluated statically (direct current), unless indicated differently, and determined at 20° C., unless indicated differently. 
     Any suitable magnetic material can be used for a magnetically conductive and/or soft magnetic layer. Crystalline alloys including any two or all three of iron, cobalt, or nickel can be used. Additional elements can optionally be added to modify properties such as magnetostriction, resistivity, permeability, saturation induction, coercivity, remanence, and/or corrosion, for example. Examples of such alloys include NiFe, NiFeMo, Fe Si, FeAlSi, and FeCo. Amorphous alloys may also be used. For example, amorphous alloys including cobalt and/or iron with metalloids such as silicon and boron may be used. Such alloys are known in the art. Nanocrystalline materials such as nanocrystalline alloys may also be used. For example, nanocrystalline alloys including iron, silicon and/or boron, and optional other elements added to control the nucleation and growth of nanocrystals on annealing may be used. Many of these alloys include iron, silicon, boron, niobium, and copper. Useful FeSiBNbCu alloys include those available from VACUUMSCHMELZE GmbH &amp; co. under the tradename VITROPERM and those available from Hitachi Metals, Ltd. under the tradename FINEMET. Ferrites can also be used. Ferrites include oxides of iron and at least one other metal. Examples of useful ferrites include soft cubic ferrite materials, such as MnZn-ferrites or NiZn-ferrites. Such materials are available from many suppliers, such as Ferroxcube. 
     In some embodiments, a magnetically conductive and/or soft magnetic layer includes a metal such as an alloy, for example. In some embodiments, the alloy is an iron alloy. In some embodiments, the alloy includes iron and at least one of silicon, aluminum, boron, niobium, copper, cobalt, nickel, or molybdenum. In some embodiments, the alloy includes iron and at least one of silicon, boron, niobium, or copper. In some embodiments, the alloy includes iron, silicon, and boron, and in some embodiments, the alloy further includes niobium and copper. In some embodiments, the alloy includes iron and at least one of silicon and aluminum. In some embodiments, the alloy includes iron, aluminum and silicon. In some embodiments, the alloy includes nickel and iron. In some embodiments, the alloy includes iron, cobalt and nickel. In some embodiments, the alloy includes nickel, iron and molybdenum. In some embodiments, the alloy includes iron and silicon. In some embodiments, the alloy includes nickel, iron and molybdenum. In some embodiments, the alloy is a crystalline alloy. In some embodiment, the crystalline alloy includes at least two different metals selected from iron, cobalt and nickel. In some embodiments, the alloy is a nanocrystalline alloy. In some embodiments, the nanocrystalline alloy includes iron, silicon, boron, niobium, and copper. In some embodiments, the alloy is an amorphous alloy. In some embodiments, an amorphous alloy includes at least one of cobalt or iron, and at least one of silicon or boron. In some embodiments, a magnetically conductive and/or soft magnetic layer includes a ferrite, such as a manganese-zinc ferrite or a nickel-zinc ferrite. 
     In some embodiments, a continuous electrically conductive layer of the iron alloy is used as a magnetically conductive and/or soft magnetic layer. In some embodiments, a magnetically conductive layer or a soft magnetic layer includes particles (e.g., magnetically conductive filler) dispersed in a binder (e.g., at least one of a thermoset adhesive, an epoxy, or a mixture including an epoxy). The magnetically conductive filler can be or include particles of any of the magnetic materials described above. In some embodiments, the particles are metallic particles which may be or include an iron-silicon-boron-niobium-copper alloy, for example, or which may be or include an iron-aluminum-silicon alloy (e.g., sendust), for example. In some embodiments, the particles are ferrite particles such as manganese-zinc ferrite particles or nickel-zinc ferrite particles. Other suitable materials for the particles, or for a continuous magnetically conductive and/or soft magnetic layer, include permalloy, molybdenum permalloy, and supermalloy. Combinations of different particles may also be used. In some embodiments, the particles include metallic particles which include at least one of an iron-silicon-boron-niobium-copper alloy or an iron-aluminum-silicon alloy. The particles can have any suitable shape and size. In some embodiments, the particles are flakes. A flake may have a thickness small (e.g., smaller by a factor of at least 4, or at least 8) compared to a largest lateral dimension of the flake and may have an irregular edge shape, for example. 
     Useful electrically conductive magnetically insulative materials include substantially non-magnetic metals such as non-ferrous metals and austenitic stainless steels, for example. A non-ferrous metal is a metal, which may be an elemental metal or a metal alloy, which does not contain iron in appreciable amounts (e.g., no iron, or only small amounts (e.g., trace amounts) of iron that do not materially affect the magnetic properties of the metal). Useful non-ferrous metals include aluminum, copper, zinc, lead, silver and alloys thereof, for example. In some embodiments, an electrically conductive magnetically insulative layer used in an antenna or coil is or includes a metal which may be or include copper or a copper alloy, for example. 
     In some aspects of the present description, methods of efficiently making coil(s) or antenna(s) are described. In some embodiments, a method of making a coil or antenna includes the step of winding a film having at least one electrically conductive layer around a rod to form an assembly as described further elsewhere herein. The film may include one or more metal layers, for example. Using multiple thinner metal layers allows winding the film around the rod to form loops or turns substantially concentric with the rod to be carried out more easily than if a single metal layer having the same total thickness (e.g., to provide substantially the same low-frequency resistance along the length) were used, for example. In some cases, multiple thinner layers are advantageously used to provide increased surface area which reduces the buildup of the effective electrical resistance of the coil due to the decrease in skin depth at higher frequencies. In some embodiments, a method of making coil(s) or antenna(s) include slicing through the assembly with one or more diamond wires to form section(s) of the assembly that include the coil(s) or antenna(s). This slicing, or other methods, can generate a regular pattern (e.g., a regular pattern of substantially parallel grooves) on one or both sides of the coil or antenna. Such regular patterns are described further elsewhere herein. 
     Substantially concentric objects (e.g., substantially concentric loops in a coil) have a same or close center (e.g., centered to within 20%, or within 10%, or within 5% of a largest lateral dimension (e.g., diameter of outermost loop)). Substantially concentric loops can have a substantially circular, elliptical, or rounded rectangular shape, for example. 
     The multilayer film can include adjacent layers bonded to one another through an adhesive layer and adjacent loops of the coil or antenna can be bonded to one another through an adhesive layer. Useful adhesives may be one or more of thermoset adhesives, epoxies, acrylates, or polyurethanes, for example. 
     The present application is related to U.S. Prov. Appl. No. 62/725,649, filed on Aug. 31, 2018 and titled “Coil and Method of Making Same”, which is hereby incorporated herein by reference in its entirety. 
       FIGS.  1 A- 1 B  are a schematic top and side views of a coil  100  according to some embodiments. The coil  100  may be, or may be used in, an antenna for transfer of information or energy. The coil or antenna  100  includes a first layer  10  having a width W, a thickness T, and extending longitudinally along a length of the first layer  10  between first  11  and second  12  longitudinal ends of the first layer  10 . The antenna  100  further includes a second layer  20  bonded to the first layer  10  along the length of the first layer  10 . The first and second layers  10  and  20  are wound to form a plurality of substantially concentric loops  110 . A width W 1  and a length of the second layer are substantially co-extensive with the respective width W and length of the first layer so as to expose opposing longitudinal edge surfaces  13  and  14  of the first layer  10  along the length of the first layer  10 . In some embodiments, the first layer  10  is an electrically conductive magnetically insulative layer and the second layer  20  is a magnetically conductive layer. The second layer  20  has opposing longitudinal edge surfaces  21  and  26  along the length of the second layer  20  and has first and second longitudinal ends  27  and  28 . Longitudinal edge surfaces of a layer extend in a longitudinal direction (e.g., longitudinal direction  123  depicted in  FIG.  3 A ) of the layer while longitudinal ends of a layer are disposed at ends of the layer opposite one another in the longitudinal direction. 
     If a first length or width of a first layer is substantially co-extensive with a first length or width of a second layer, the respective lengths or widths substantially overlap each other (e.g., the first length or width overlaps at least 80%, or at least 90%, or at least 95% of the second length or width; and the first length or width overlaps at least 80%, or at least 90%, or at least 95% of the first length or width). 
     In some embodiments, the antenna or coil  100  further includes at least one third layer  17  bonded to the first layer  10  along the length of the first layer  10 . Each third layer  17  has a width and a length substantially co-extensive with the respective width and length of the first layer  10 . The first layer  10 , the second layer  20 , and the at least one third layer  17  are wound to form the plurality of substantially concentric loops  110 . Each third layer  17  has opposing longitudinal edge surfaces  33  and  34  along the length of the second layer  20  and has first and second longitudinal ends  18  and  19 . 
     In some embodiments, the coil  100  includes first adhesive layer(s)  30  bonding the first layer  10  and the at least one third layer  17  and includes a second adhesive layer  42  disposed between and bonding adjacent loops  110 . In some embodiments, the second adhesive layer  42  is thicker (e.g., by at least a factor of 1.5 or 2) than the first adhesive layer  30 . The coil  100  further includes a third adhesive layer  40  bonding the first layer  10  to second layer  20 . In some embodiments, the third adhesive layer  40  is thicker (e.g., by at least a factor of 1.5 or 2) than the first adhesive layer  30 . In some embodiments, the at one third layer  117  includes at least one electrically conductive magnetically insulative layer. In some embodiments, the at least one third layer  117  includes at least one magnetically conductive layer. 
     In some cases, the first layer  10  and each third layer  17  are similar in composition, shape or function, for example. In such cases, or in other cases, the first layer  10  together with the one or more third layers  17  may be described as a plurality of first layers. It will be understood that alternate nomenclatures can be used for the various layers. For example, the layer  20  may be described as a first layer and the layer  10  together with the one or more third layers  17  may be described as a plurality of second layers. 
     The thicknesses and widths of the various layers may be selected to be any suitable values. In some embodiments, thinner first layers  10  and/or third layers  17  are selected when it is desired for the coil or antenna to operate at higher frequencies, and thicker first layers  10  and/or third layers  17  are selected when it is desired for the coil or antenna to operate at lower frequencies. At higher frequencies, current can become partially confined to a skin layer at the surface of the conductor and this tends to increase the effective electrical resistance of the coil. Using multiple first layers  10  and/or third layers  17  distributes the current over more surfaces and this can reduce the effects of the reduced skin depth on the effective electrical resistance of the coil. In some embodiments, each of the first layers  10  and/or third layers  17  have a thickness of at least 5 microns, or at least 10 microns, or at least 20 microns, or at least 40 microns. In some embodiments, each of the first layers  10  and/or third layers  17  have a thickness of no more than 2000 microns, or no more than 1000 microns, or no more than 500 microns, or no more than 250 microns. For example, in some embodiments, 1000 microns≥T≥10 microns. The width (e.g., W or W 1 ) of a layer may be less than, comparable to (e.g., equal to within 20%, or with 10%), or greater than the thickness of the layer. In some embodiments, a ratio of the width to a thickness of the first layer  10  is at least 0.1, or at least 1, or at least 5 (i.e., in some embodiments, W/T≥0.1, or W/T≥1, or W/T≥5). For example, in some embodiments, 1000≥W/T≥0.1. The second layer  20  has a thickness T 1 . In some embodiments, a ratio of the width to a thickness of the second layer  20  is at least 0.1, or at least 1, or at least 5, or at least 10 (i.e., in some embodiments, W 1 /T 1 ≥0.1, or W 1 /T 1 ≥1, or W 1 /T 1 ≥5, or W 1 /T 1 ≥10). For example, in some embodiments, 1000≥W 1 /T 1 ≥0.1. In some embodiments, the thickness T of the first layer  10  is greater than the thickness T 1  of the second layer  20 . In other embodiments, the thickness T of the first layer  10  is less than the thickness T 1  of the second layer  20 . In some embodiments, the thicknesses T and T 1  of the first and second layers  10  and  20  are about equal. The length of any of the layers layer may be substantially longer than the width or thickness of the layer (e.g., the length may be at least 5 times or at least 10 times one or both of the width and the thickness). 
     In some embodiments, the antenna or coil  100  can be described as including a multilayer film  202  wound to form the plurality of substantially concentric loops  110  where the multilayer film  202  includes a first layer  20  and a plurality of second layers ( 10  and  17 ) disposed on and bonded to the first layer  20 . The first layer  10  and the at least one third layer  17  may be disposed on a same side as the second layer  20 , or one or more of the first layer  10  and the at least one third layer  17  may be disposed on one same side of the second layer  20  and the remaining layers of the first layer  10  and the at least one third layer  17  may be disposed on the opposite side of the second layer  20 . 
     In some embodiments, the multilayer film  202  includes a first layer (e.g., layer  20 ), and a plurality of alternating second (e.g., layers  10  and  17 ) and third (e.g., layer  30 ) layers disposed on and bonded to the first layer. In some embodiments, the first layer is a magnetically conductive layer, the second layers are electrically conducive magnetically insulative layers, and the third layers are electrically and magnetically insulative. The first layer may have a relative permeability in any of the ranges described elsewhere herein for magnetically conductive layers. The first layer may be electrically conductive or electrically insulative. The second and/or third layers may have a relative permeability in any of the ranges described elsewhere herein for magnetically insulative layers. Each third layer may be an adhesive (e.g., a thermoset adhesive and/or an epoxy). In some embodiments, widths and lengths of the first, second and third layers are substantially co-extensive with each other so that no longitudinal edge surface (e.g., edge surfaces  13  and  14 ) of a second layer is covered by either a third layer or the first layer. 
     The antenna or coil  100  includes opposing major surfaces  76  and  77 . One or both of the major surfaces  76  and  77  may include a regular pattern (e.g., regular pattern of substantially parallel grooves) as described further elsewhere herein. For example, in some embodiments, the regular pattern may be described in any one or more of the following ways. The regular pattern may extend substantially along a same first direction and across substantially the entire coil. The regular pattern may extend along a first direction making an angle θ with a longitudinal direction of the loop where θ varies along the longitudinal direction of the loop. The regular patterns of the edge surfaces of at least a plurality of adjacent loops of the separated portion of the multilayer film may be substantially aligned with each other. The regular pattern may include a pattern of substantially parallel grooves extending across at least a plurality of adjacent loops of the separated portion of the multilayer film. The regular pattern may have a first average pitch in a first region of the coil and a different second average pitch in a different second region of the coil. A Fourier transform of the regular pattern may have a peak at a first spatial frequency in a first region of the coil and a peak at a different second spatial frequency in a different second region of the coil. The coil may include, in at least one first region of the coil, a regular optical and topographical pattern along a first direction, and a regular optical, but not topographical, pattern along an orthogonal second direction. 
       FIG.  1 C  is a schematic cross-sectional view of the multilayer film  202  in a cross-section perpendicular to a longitudinal direction of the loops  110 . The multilayer film  202  has a substantially rectangular cross-section. For example, the cross-section may be nominally rectangular, or may be rectangular except for rounded corners having radius of curvature large compared to the film thickness (e.g., at least 5 times, or at least 10 times, or at least 20 times) and/or except for having opposite sides that deviate from parallel by no more than 20 degrees, or no more than 10 degrees, or no more than 5 degrees. The rectangle can be longer or shorter or in the x-direction than in the y-direction depending on the widths and thicknesses of the various layers. Substantially rectangular cross-sections also include substantially square cross-sections since square can be considered to be a special case of a rectangle. In some embodiments, for each loop in the plurality of substantially concentric loops  110 , the multilayer film  202  has a substantially rectangular cross-section in a plane perpendicular to a longitudinal direction of the loop. In some embodiments, each loop in the plurality of concentric loops  110  has a substantially rectangular cross-section in a plane perpendicular to the longitudinal direction of the loop. 
       FIG.  1 D  is a schematic top view of an assembly  101  including the coil  100  and a rod  37 . As described further elsewhere herein, the assembly  101  can be made by wrapping a multilayer film around a rod and cutting (e.g., slicing with a wire saw) the resulting assembly to provide a desired width of a portion of the assembly separated by the cutting. The rod  37  may be a sliced segment of the initial rod used in forming the assembly  101 . 
     The first layer  10  and the optional at least one third layer  17  may each be one or more of an electrically conductive magnetically insulative layer, a metal layer, a non-ferrous metal layer, or a substantially non-magnetic metal layer and may have a conductivity and/or relative permeability in any of the corresponding ranges described elsewhere herein and may be made of corresponding materials described elsewhere herein (e.g., copper or copper alloy). The second layer  20  may be one or more of a magnetically conductive layer or a soft magnetic layer and may have a relative permeability and/or a coercivity in any of the corresponding ranges described elsewhere herein and may be made of corresponding materials described elsewhere herein (e.g., particles of an iron-silicon-boron-niobium-copper alloy in a binder). In some embodiments, each loop includes at least one metal layer (e.g., layer  10 ) having a relative permeability less than 1.1 and at least one layer (e.g., layer  20 ) having a relative permeability of at least 10. In some embodiments, each loop  110  includes at least one substantially non-magnetic metal layer (e.g., layer  10 ) and at least one soft magnetic layer (e.g., layer  20 ). In some embodiments, each loop  110  includes at least one electrically conductive magnetically insulative layer (e.g., layer  10 ) and at least one magnetically conductive layer (e.g., layer  20 ). In some embodiments, each loop  110  includes at least one first layer (e.g., layer  10  and/or  17 ) having an electrical resistivity of less than 100 μΩcm and a relative permeability of less than 1.4 and at least one second layer (e.g., layer  20 ) having a relative permeability of greater than 2 and a coercivity of less than 1000 A/m. In some embodiments, each loop includes at least one first layer (e.g., layer  10  and/or  17 ) having an electrical resistivity of less than 100 μΩcm and a relative permeability of less than 1.1 and at least one second layer (e.g., layer  20 ) having a relative permeability of greater than 10 and a coercivity of less than 100 A/m. 
     In some embodiments, a coil or antenna  100  for transfer of information or energy includes an electrically conductive magnetically insulative first layer  10  includes opposing major surfaces  15  and  16  and opposing edge surfaces  13  and  14  connecting the opposing major surfaces  15  and  16 ; and a magnetically conductive second layer  20  disposed on and bonded to the first layer  10  and substantially co-extensive in length and width of the first layer  10  so as to not cover edge surfaces  13  and  14  of the first layer, where the first and second layers  10  and  20  are wound to form a plurality of substantially concentric loops  110 . 
     In some embodiments, the coil  100  is substantially planar. For example, the coil  100  may be disposed primarily in a plane parallel to the x-y plane of  FIGS.  1 A- 1 D  referring to the illustrated x-y-z coordinate system and any radius of curvature of a cross-section of the coil in a plane perpendicular to plane of the coil is large (e.g., at least 5 times, or at least 10 times, or at least 20 times) compared to a diameter or largest lateral dimension of the coil. 
     In some embodiments, a substantially planar coil  100  for transfer of information or energy includes an electrically conductive magnetically insulative first layer  10 , and a magnetically conductive second layer  20  disposed on and bonded to the first layer  10  and substantially co-extensive in length and width of the first layer so as to not cover edge surfaces  13  and  14  of the first layer  10 . 
     In some embodiments of the antenna or coil  100 , corresponding edge surfaces ( 13 ,  21  and  14 ,  22 ) of the first and second layers  10  and  20  are substantially co-planar (see. e.g., planes S 1  and S 2  depicted in  FIGS.  4  and  5 A ). The methods described elsewhere herein can, in some embodiments, ensure that the second layer  20  is substantially co-extensive in length and width of the first layer so as to not cover edge surfaces  13  and  14  of the first layer  10  and can, in some embodiments, form corresponding edge surfaces of the first and second layers  10  and  20  that are substantially co-planar. 
     The coil  100  is wound into loops with the second layer  20  outside the first layer  10 . The coil can alternatively be wound into loops with the first layer  10  outside the second layer  20 .  FIG.  2    is a schematic top view of an antenna or coil  200  wound with the first layer  10  outside the second layer  20 . In the illustrated embodiment, the coil  200  includes at least one third layer  17  with the first layer  10  disposed between the second layer  20  and the at least one third layer  17 . 
       FIGS.  3 A- 3 B  are schematic top views of an antenna or coil  300  where at least one of the opposing longitudinal edge surfaces of the first layer  10  includes a regular pattern  120 .  FIG.  3 C  is a schematic bottom view of the antenna or coil  300  according to some embodiments. The regular pattern  120  may be a regular pattern of grooves, for example. In some embodiments, the longitudinal edge surface  13  includes a first regular pattern (e.g., appearing as regular pattern  120  in top plan view) and the longitudinal edge surface  14  includes a second regular pattern (e.g., appearing as regular pattern  120   b  in bottom plan view). In other embodiments, the regular pattern is present in only one or the other of the top and bottom plan views. The coil  100  and/or  200  may include the regular pattern(s) described for coil  300 , for example. 
     In some embodiments, each loop  110   a  in the plurality of substantially concentric loops  110  has an edge surface  111  substantially perpendicular (e.g., within 20 degrees, or 10 degrees, or 5 degrees to perpendicular) to an adjacent loop  110   b  and includes a regular pattern  120 . In some embodiments, the regular pattern  120  extends along a first direction  122  making an angle θ with a longitudinal direction  123  of the loop  110  where θ varies along the longitudinal direction  123  of the loop  110 . In some embodiments, the regular pattern  120  extends substantially laterally across the edge surface  111  (e.g., within 20 degrees, or within 10 degrees, or within 5 degrees, or within 3 degrees of a plane of the major surface of the coil including the edge surface  111  (e.g., parallel to the x-y plane)). In some embodiments, the regular pattern  120  extends substantially laterally across the edge surface  111  substantially along a same first direction  122 . In some embodiments, the regular patterns  120  of the edge surfaces  111  of at least a plurality of adjacent loops  110  are substantially aligned with each other. In some embodiments, each loop includes a second edge surface  111   b  (see, e.g.,  FIG.  3 C ) opposite the edge surface  111  (first edge surface), where the second edge surface  111   b  includes a second regular pattern  120   b  which may also extend along the first direction  122  and which may also extend substantially laterally across the second edge surface  111   b.    
     The second regular pattern  120   b  may have any of the attributes described further elsewhere herein for the regular pattern  120 . For example, the second regular pattern  120   b  may be a regular pattern of substantially parallel grooves extending across at least a plurality of adjacent loops in the plurality of substantially concentric loops. 
     In some embodiments, the substantially concentric loops refer to loops of a multilayer film, for example. Each loop  110  may include loops of adjacent layers  10  and  17  and the edge surface  111  may be an edge surface of the combined adjacent layers  10  and  17 . In some embodiments, the substantially concentric loops refer to loops of individual layers in a multilayer film, for example. For example, the first layer  10  is wound into substantially concentric loops. In such cases, the edge surface  111  may be an edge surface (e.g., edge surface  13 ) of a first layer  10 , for example. 
     In some embodiments, each loop  110  includes at least one layer (e.g., layer  20 ) that is a soft magnetic layer and/or a magnetically insulative layer and at least one layer (e.g., layer  10  and/or  17 ) that is an electrically conductive layer such as a metal layer. In some embodiments, the optional at least one third layer  17  is omitted. In some embodiments, each loop includes a plurality of electrically conductive or metal layers (e.g., layers  10  and  17 ). In some embodiments, each loop includes two or more soft magnetic and/or magnetically insulative layers. 
     In some embodiments, the coil  300  includes a plurality of substantially concentric loops  110  where each loop includes a plurality of substantially concentric metal layers ( 10  and  17 ) substantially concentric with at least one soft magnetic layer  20 , such that in a plan view (e.g., the top plan view of  FIG.  3 A or  3 B  and/or the bottom plan view of  FIG.  3 C ), the coil  300  includes a regular pattern  120  of substantially parallel grooves  121  extending across at least a plurality of adjacent loops in the plurality of substantially concentric loops  110 . In some embodiments, in the top plan view, the coil includes the regular pattern  120  (first regular pattern) and in a bottom plan view, the coil includes a regular pattern  120   b  (second regular pattern). In some embodiments, each of the first and second regular patterns include a pattern of substantially parallel grooves. In some embodiments, the first and second regular patterns extend in substantially same first direction  122 . 
     In some embodiments, the at least one soft magnetic layer of each loop is disposed between the plurality of substantially concentric metal layers of the loop and the plurality of substantially concentric metal layers of an adjacent loop. In some embodiments, a first adhesive layer  30  is disposed between and bonds adjacent metal layers in the plurality of substantially concentric metal layers, and a second adhesive layer  42  is disposed between and bonds adjacent loops. In some embodiments, the second adhesive layer  42  is thicker than the first adhesive layer  30 . 
     In some embodiments, the plurality of substantially concentric metal layers in each loop are electrically connected to each other. For example, the metal layers in each loop may be welded together at one or both ends of the loop or may be electrically connected to one another at one or both ends of the loop when the coil is connected to electrical cable(s) by soldering, for example. A weld  15  is schematically illustrated in  FIG.  3 B . The opposite ends of the layers  10  and  17  may also optionally be welded or soldered to provide an electrical connection between the layers 
     In some embodiments, the antenna or coil  300  includes a plurality of substantially concentric loops  110 , where each loop includes a metal layer (e.g., layer  10 ). Each loop may further include at least one soft magnetic layer and/or may include a plurality of alternating metal and first adhesive layers as described further elsewhere herein. In some embodiments, in a plan view (e.g., the top plan view of  FIG.  3 A ), the coil  300  includes a regular pattern  120  extending substantially along a same first direction  122  (e.g. extending along the first direction  122  to within 20 degrees, or within 10 degrees, or within 5 degrees of the first direction  122 ) and across substantially the entire coil  300  (e.g., across at least 80%, or at least 90%, or at least 95% of an area of the coil). The regular pattern  120  can be described in terms of an average pitch in various regions and/or in terms of a Fourier transform of the regular pattern in the various regions. In some embodiments, the regular pattern has a first average pitch P 1  in a first region  125  of the coil and a different second average pitch P 2  in a different second region  130  of the coil. In some embodiments, a difference between the first and second average pitches is greater than about 10 microns, or greater than about 15 microns, or greater than about 20 microns, or greater than about 30 microns, or greater than about 40 microns, or greater than about 50 microns. For example, the first average pitch P 1  may be in a range of about 60 microns to about 100 microns, and the second average pitch P 2  may be in a range of about 120 microns to about 200 microns. In some embodiments, one or both of the first and second average pitches are in a range from 5 microns, or 10 microns, or 20 microns, or 40 microns to 2000 microns, or 1000 microns, or 500 microns, or 250 microns. 
     In some embodiments, a Fourier transform of the regular pattern has a peak at a first spatial frequency (see, e.g., F 1  depicted in  FIG.  14   ) in a first region  125  of the coil and a peak at a different second spatial frequency (see, e.g., F 2  depicted in  FIG.  21   ) in a different second region  130  of the coil. The peaks in the Fourier transforms may correspond to average pitches in the regular pattern (e.g., F 1  may be about 1/P 1  and F 2  may be about 1/P 2 ). In some embodiments, one or both of the first and second spatial frequencies are in a range from 1/(2000 microns), or 1/(1000 microns), or 1/(500 microns), or 1/(250 microns) to 1/(5 microns), or 1/(10 microns), or 1/(20 microns), or 1/(40 microns). In some embodiments, a difference between the first and second spatial frequencies is greater than about 0.001 inverse microns, or greater than about 0.002 inverse microns, or greater than about 0.004 inverse microns, or greater than about 0.01 inverse microns, or greater than about 0.02 inverse microns, or greater than about 0.05 inverse microns, or greater than about 0.1 inverse microns. 
     Third and fourth regions  131  and  139  are also illustrated in  FIG.  3 B . The pitch and Fourier transform can be evaluated in each of these regions as described further elsewhere herein. 
     In some embodiments, coils or antennas (e.g.,  100 ,  200 , or  300 ) of the present description can be described as including a multilayer film wound to form a plurality of substantially concentric loops (e.g., loops  110 ). 
       FIG.  4    is a schematic end view of an embodiment of a multilayer film  402  including a first layer  10  and a second layer  20 . First layer  10  may be an electrically conductive magnetically insulative layer and second layer  20  may be a magnetically conducive layer and/or a soft magnetic layer. In some embodiments, the first layer  10  and the second layer  20  are bonded to one another through an adhesive  40 . In some embodiments, a multilayer film includes two multilayer films  402  with adhesive  42  of one the films bonded to the first layer  10  of the other films. In such embodiments, the multilayer film includes two first layers  10  and two second layers  20 . In some embodiments, an antenna or coil includes the multilayer film  402  wound into a plurality of loops. In some embodiments, adhesive  42  bonds adjacent loops to one another. 
     In some embodiments, the multilayer film  402  includes an electrically conductive magnetically insulative first layer  10 , and a magnetically conductive second layer  20  disposed on and bonded to the first layer  10 , such that corresponding edge surfaces of the first and second layers  10  and  20  are substantially co-planar (e.g., co-planar to within deviations from a common plane of less than 0.3, or less than 0.2, or less than 0.1, or less than 0.05 times the thickness of the multilayer film). In the illustrated embodiments, the edge surface  13  of the first layer  10  and the edge surface  21  of the second layer  20  are corresponding edge surfaces in the plane S 1 , and the edge surface  14  of the first layer  10  and the edge surface  24  of the second layer  20  are corresponding edge surfaces in the plane S 2 . 
     In some embodiments, a multilayer film includes additional first layers  10  and/or additional second layers  20 .  FIG.  5 A  is a schematic end view of the multilayer film  502  including a first layer  20  and a plurality of alternating second and third layers  10  and  30 .  FIG.  5 B  is a schematic side view of the multilayer film  502 . In some embodiments, the multilayer film  502  includes a magnetically conductive first layer  20 ; and a plurality of alternating second  10  and third  30  layers disposed on and bonded to the first layer  20 , where the second layers  10  are electrically conductive and magnetically insulative, and the third layers  30  are electrically and magnetically insulative. In some embodiments, widths (W 1 , W, W 2 ) and lengths (L 1 , L, L 2 ) of the first, second and third layers  20 ,  10 , and  30  are substantially co-extensive with each other so that no longitudinal edge surface ( 13 ,  14 ) of a second layer  10  is covered by either a third layer  30  or the first layer  20 . In some embodiments, a ratio of the width to a thickness of the first layer  20  is at least 0.1, or at least 1, or at least 5. 
     In some embodiments, a coil includes a multilayer film (e.g.,  202 , or  402  or  502 ) wound to form a plurality of substantially concentric loops (e.g., loops  110 ). In some embodiments, the multilayer film includes a plurality of alternating electrically conductive  10  and first adhesive  30  layers and includes a second adhesive layer  42  including an outermost major surface  44  of the multilayer film. The second adhesive layer  42  can optionally be disposed at the opposite outermost major surface from that illustrated in  FIGS.  4 - 5 B . In some embodiments, as described further elsewhere herein, a method of making a coil includes winding the multilayer film around the rod to form an assembly including the rod and a plurality of loops of the multilayer film substantially concentric with the rod where each loop is bonded to an adjacent loop through the second adhesive layer  42 . 
     A film may have two dimensions much larger than a third dimension. A film strip may be cut out from the film such that the strip has one dimension much larger than the other two dimensions. A multilayer film used in a coil or antenna of the present description may be a film strip or a portion of a film strip. 
       FIG.  6    is a top view of an assembly  601  including a coil  600  and a rod or rod section  637 . The coil  600  includes a plurality of substantially concentric loops  110 .  FIG.  7 A  is a laser intensity image of a portion of a coil corresponding to coil  600  obtained using a Keyence VHX-5000 digital microscope fitted with a Z20 lens at 150× magnification.  FIG.  7 B  is a schematic top plan view of a portion of a coil which may correspond to coil  600 . The coil of  FIG.  7 B  is considered to have a curvature large compared to the size of the illustrated portion so that the curvature is not shown in the schematic illustration of  FIG.  7 B . 
     In some embodiments, the coil includes a plurality of substantially concentric loops where each loop is a loop of a multilayer film (e.g., loops  110  depicted in  FIG.  7 B  include a plurality of layers  10  and  30 ). In some embodiments, the coil includes a plurality of substantially concentric loops where each loop is a loop of a first layer (e.g., loops  10   a  and  10   b  depicted in  FIG.  7 A or  7 B  are each loops of a single layer  10 ). In some embodiments, a coil  600  includes a plurality of substantially concentric loops  110 , where each loop includes a plurality of substantially concentric alternating metal  10  and first adhesive layers  30  (e.g., each of the loops  110   a  and  110   b  depicted in  FIG.  7 A or  7 B  each include alternating layers  10  and  30 ). In some embodiments, each metal layer includes a non-ferrous metal, and/or is magnetically insulative, and/or is substantially non-magnetic. 
     A second adhesive layer  41  is disposed between and bonds adjacent loops  110 . In some embodiments, the second adhesive layer  41  is thicker than the first adhesive layer  30 . In some embodiments, the second adhesive layer  41  is thicker than the first adhesive layer by at least a factor of two, of by at least a factor of four. In some embodiments, the second adhesive layer  41  includes a magnetically conductive filler dispersed in a binder. 
     In some embodiments, the second adhesive layer  41  includes opposing first and second adhesive portions  40  and  42  on opposite major surfaces of a composite portion  20 . The composite portion  20  includes particles  43 , which may be magnetically conductive filler particles, dispersed in a binder (e.g., epoxy). In some embodiments, each of the adhesive portions  40  and  42  and the composite portions  20  include a common type of adhesive material. For example, in some embodiments, each of the adhesive portions  40  and  42  and the composite portion  20  includes epoxy. In some embodiments, the composite portion  20  includes magnetically conductive filler particles dispersed throughout the composite portion  20  in order to increase the relative permeability of the composite portion  20 , for example. The particles  43  may be metal particles which may include an iron-silicon-boron-niobium-copper alloy, for example, and which may have any suitable shape (e.g., at least one of flakes, plates, spheres, ellipsoids, irregularly shaped particles). 
     In some embodiments, an antenna or coil includes a plurality of substantially concentric loops  110 , where each loop includes a plurality of substantially concentric alternating metal  10  and first adhesive layers  30 , and where a second adhesive layer  41  is disposed between and bonds adjacent loops. In some embodiments, the second adhesive layer thicker than the first adhesive layer (e.g., by at least a factor of 2 or 4). In some embodiments, each of the first and second adhesive portions  40  and  42  is thicker than each first adhesive layer  30 . In some embodiments, the composite portion  20  is thicker than each of the first and second adhesive portions  40  and  42 . In some embodiments, the first and second adhesive portions  40  and  42  have a substantially (e.g., to within 20%, or to within 10%, or to within 5%) same thickness. 
     In some embodiments, the antenna or coil includes a multilayer film wound to form a plurality of substantially concentric loops, where the multilayer film includes a magnetically conductive first layer  20  and a plurality of alternating second  10  and third  30  layers. The first layer  20  is bonded to the plurality of alternating second  10  and third  30  layers through and adhesive layer  40 . Adjacent loops are bonded together through adhesive layer  42 . In some embodiments, the adhesive layer  42  is thicker than each layer  30 . In some embodiments, the adhesive layer  42  is thicker than each layer  30  by at least a factor of 1.5, or by at least a factor of 2. 
       FIGS.  8 A- 8 B  are a laser intensity image and a topographical map, respectively, of a coil or antenna  800  in a first region (e.g., corresponding to first region  125  depicted in  FIG.  3 B ) of the antenna  800  in a top plan view (e.g., in the x-y plane referring to the x-y-z coordinate system depicted in  FIG.  8   ) obtained using a Keyence VK-X200 confocal microscope with a 20x objective. In some embodiments, the antenna  800  is for transfer of information or energy and includes a plurality of substantially concentric loops  110  where each loop includes a metal layer  10 . In some embodiments, each loop  110  includes a plurality of metal layers  10  (e.g., four metal layers  10  in the illustrated embodiment). Coil or antenna  800  was made from a multilayer film including 4 copper layers bonded together with 10 micron thick epoxy adhesive layers  30 , and an adhesive layer  41  which included a composite layer (e.g., corresponding to layer  20  depicted in  FIG.  7 B ) having a thickness of about 60 micrometers bonded to the copper layers with a 20 micron thick epoxy adhesive layer (e.g., corresponding to layer  40  depicted in  FIG.  7 B ) and having a 20 micron thick epoxy adhesive layer (e.g., corresponding to layer  42  depicted in  FIG.  7 B ) for bonding adjacent loops of the multilayer film together. The copper layers had a thickness of about 105 microns. The composite layer included flakes of magnetic metal (sendust) dispersed in epoxy. The coil or antenna  800  was made by winding the multilayer film around a rod to form a plurality of substantially concentric loops and slicing the coil or antenna  800  from the resulting assembly using a diamond wire saw as described further elsewhere herein. 
       FIG.  9    is a topographical map of a portion of the first region obtained using the Keyence VK-X200 confocal microscope.  FIG.  10    is a plot of the topography (height of surface relative to a reference plane) along the x-direction and  FIG.  11    is a plot of the topography (height) along the y-direction in the first region. The plots in  FIGS.  10 - 11    were extracted from the topological map obtained using the Keyence VK-X200 confocal microscope. It can be seen in  FIGS.  8 A- 9    that an optical pattern is present in both the x- and y-directions. It can be seen in  FIG.  10    that there is substantially no topographical pattern along the y-direction across the plurality of metal layers. It can be seen in  FIG.  11    that there is a substantial topographical pattern along the y-direction across the plurality of metal layers. The topological pattern in the first region had an average pitch P 1  in the y-direction of about 89 microns (determined by approximating the average pitch as the inverse of the corresponding Fourier transform peak frequency). In some embodiments, in a plan view (e.g., in the x-y plane) and in at least one first region  125  of the antenna or coil, the antenna or coil includes a regular optical and topographical pattern  120  along a first direction (y-direction), and a regular optical, but not topographical, pattern along an orthogonal second direction (x-direction). In some embodiments, in a top plan view and in at least one first region  125  of the antenna or coil, the antenna or coil includes a first regular optical and topographical pattern  120  along a first direction (y-direction), and a first regular optical, but not topographical, pattern along an orthogonal second direction (x-direction); and in a bottom plan view and in at least one first region  125  of the antenna or coil, the antenna or coil includes a second regular optical and topographical pattern  120   b  (schematically depicted in  FIG.  3 C ) along the first direction, and a second regular optical, but not topographical, pattern along an orthogonal second direction. 
     In some embodiments, the regular optical and topographical pattern  120  and/or  120   b  includes a regular pattern of substantially parallel grooves extending along the second direction and spaced apart along the first direction. In some embodiments, the regular pattern of substantially parallel grooves extends across substantially the entire antenna or coil, and the regular pattern of substantially parallel grooves has a first average pitch in a first region of the antenna or coil and has a different second average pitch in a different second region of the antenna or coil. In some embodiments, the regular pattern of substantially parallel grooves extends across substantially the entire antenna and a Fourier transform of the regular pattern of substantially parallel grooves has a peak at a first spatial frequency in a first region of the antenna and a peak at a different second spatial frequency in a different second region of the antenna. 
       FIG.  12    is a plot of the magnitude of a two-dimensional Fourier transform of the surface topography in the first region.  FIG.  13    is a plot of the magnitude of Fourier transform along the x-direction and  FIG.  14    is a plot of the magnitude Fourier transform along the y-direction in the first region. The Fourier transform along the y-direction has a peak K 1  at a spatial frequency F 1 . The peak K 1  is indicative of the periodic pattern shown in  FIG.  11   . The peak K 1  is substantially spaced apart from any neighboring peak. The Fourier transform along the x-direction shown in  FIG.  13    does not have a peak at a non-zero spatial frequency that is substantially spaced apart from any neighboring peak. This indicates a lack of a topological pattern along the x-direction. 
       FIGS.  15 A- 15 B  are a laser intensity image and a topographical map, respectively, of the coil or antenna  800  in a second region (e.g., corresponding to second region  130  depicted in  FIG.  3 B ) of the coil or antenna  800  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  16    is a topographical map of a portion of the second region.  FIG.  17    is a plot of the height along the x-direction and  FIG.  18    is a plot of the height along the y-direction in the second region. The topological pattern in the second region had an average pitch P 2  in the y-direction of about 152 microns. 
       FIG.  19    is a plot of the magnitude of the Fourier transform of the surface topography in the second region.  FIG.  20    is a plot of the magnitude Fourier transform along the x-direction and  FIG.  21    is a plot of the magnitude Fourier transform along the y-direction in the second region. The Fourier transform along the y-direction has a peak K 2  at a spatial frequency F 2 . The peak K 2  is indicative of the periodic pattern shown in  FIG.  18   . The peak K 2  is substantially spaced apart from any neighboring peak having a similar magnitude. The Fourier transform along the x-direction shown in  FIG.  20    does not have any such peaks; this indicates a substantial absence of a topological pattern along the x-direction. 
       FIGS.  22 A- 22 B  are a laser intensity image and a topographical map, respectively, of the coil or antenna  800  in a third region (e.g., corresponding to third region  131  depicted in  FIG.  3 B ) of the coil or antenna  800  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  23    is a plot of the height along the y-direction. A periodic structure having an average pitch in the y-direction of about 97.1 microns is visible.  FIG.  24    is a plot of the magnitude of the Fourier transform of the surface topography in the third region.  FIG.  25    is a plot of the magnitude of the Fourier transform along the x-direction and  FIG.  26    is a plot of the magnitude of the Fourier transform along the y-direction in the third region. The pair of large peaks proximal to the zero-frequency peak in  FIG.  26    are indicative of a periodic structure along the y-direction. 
       FIGS.  27 A- 27 B  are a laser intensity image and a topographical map, respectively, of the coil or antenna  800  in a fourth region (e.g., corresponding to third region  139  depicted in  FIG.  3 B ) of the coil or antenna  800  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  28    is a plot of the height along the y-direction. A periodic structure having an average pitch in the y-direction of about 139 microns is visible.  FIG.  29    is a plot of the magnitude of the magnitude of the Fourier transform of the surface topography in the fourth region.  FIG.  30    is a plot of the Fourier transform along the x-direction and  FIG.  31    is a plot of the magnitude of the Fourier transform along the y-direction in the fourth region. The pair of large peaks proximal to the zero-frequency peak in  FIG.  31    are indicative of a periodic structure along the y-direction. 
       FIG.  32    is a top plan view of a coil  3300  having a rounded rectangular shape. First and second regions  125  and  130  of the coil are shown. A comparative coil  3300  available from Worth Electronics as part number 760308103202 which has the geometry shown in  FIG.  32    and which is a representative example of a wound copper wire-based coil was analyzed. 
       FIGS.  33 A- 33 B  are a laser intensity image and a topographical map, respectively, of the comparative coil  3300  in a first region  125  of the coil  3300  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  34    is a topographical map of a portion of the first region  125 .  FIGS.  35 A- 35 B  are plots of the height along the x-direction at smaller and larger x-coordinate length scales, respectively, and  FIG.  36    is a plot of the height along the y-direction in the first region  125 . A periodic structure having an average pitch in the x-direction of about 336 microns is visible.  FIG.  37    is a plot of the magnitude of the Fourier transform of the surface topography in the first region.  FIG.  38    is a plot of the magnitude of the Fourier transform along the x-direction and  FIG.  39    is a plot of the magnitude of the Fourier transform along the y-direction in the first region  125 . 
       FIGS.  40 A- 40 B  are a laser intensity image and a topographical map, respectively, of the comparative coil  3300  in a second region  130  of the coil  3300  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  41    is a topographical map of a portion of the second region  130 .  FIG.  42    is a plot of the height along the x-direction and  FIGS.  43 A- 43 B  are plots of the height along the y-direction at smaller and larger y-coordinate length scales, respectively, in the second region  130 . A periodic structure having an average pitch in the y-direction of about 334 microns is visible.  FIG.  44    is a plot of the magnitude of the Fourier transform of the surface topography in the second region.  FIG.  45    is a plot of the Fourier transform along the x-direction and  FIG.  46    is a plot of the Fourier transform along the y-direction in the second region  130  obtained using the Keyence VK-X200 confocal microscope. 
       FIGS.  33 A- 46    show that the topological pattern of the comparative coil  3300  had a periodicity in the x-direction in the first region  125  and a periodicity in the y-direction in the second region  130 . In each case, the topological pattern had a periodicity in the radial direction in the first and second regions and did not extend in a same direction in the two regions. 
       FIG.  47    is a top plan view of a coil  4700  having a substantially circular shape. A comparative coil  4700  available from Samsung Electronics Co. Ltd. (South Korea) which had the shape illustrated in  FIG.  47    and which is a representative example of a flexible printed circuit coil was analyzed. 
       FIGS.  48 A- 48 B  are a laser intensity image and a topographical map, respectively, of the comparative coil  4700  in a first region  125  of the coil  4700  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  48 C  is a topographical map of a portion of the first region  125 .  FIGS.  49 A- 49 B  are plots of the height along the x-direction at smaller and larger x-coordinate length scales, respectively, and  FIG.  50    is a plot of the height along the y-direction in the first region  125 . A periodic structure having an average pitch in the x-direction of about 941 microns is visible.  FIG.  51    is a plot of the magnitude of the Fourier transform of the surface topography in the first region  125 .  FIG.  52    is a plot of the magnitude of the Fourier transform along the x-direction and  FIG.  53    is a plot of the Fourier transform along the y-direction in the first region  125 . 
       FIGS.  54 A- 54 B  are a laser intensity image and a topographical map, respectively, of the comparative coil  4700  in a second region  130  of the coil  3300  in a top plan view obtained using the Keyence VK-X200 confocal microscope.  FIG.  55    is a topographical map of a portion of the second region  130 .  FIG.  56    is a plot of the height along the x-direction and  FIGS.  57 A- 57 B  are plots of the height along the y-direction at smaller and larger y-coordinate length scales, respectively, in the second region  130 . A periodic structure having an average pitch in the x-direction of about 929 microns is visible.  FIG.  58    is a plot of the magnitude of the Fourier transform of the surface topography in the second region  130 .  FIG.  59    is a plot of the Fourier transform along the x-direction and  FIG.  60    is a plot of the Fourier transform along the y-direction in the second region  130 . 
       FIGS.  48 A- 60    show that the topological pattern of the comparative coil  4700  had a periodicity in the x-direction in the first region  125  and a periodicity in the y-direction in the second region  130 . In each case, the topological pattern had a periodicity in the radial direction in the first and second regions and did not extend in a same direction in the two regions. 
     In some embodiments, a method of making a coil or antenna includes providing a rod, providing a film (e.g., a multilayer film including at least one electrically conductive layer, or any of the multilayer films described elsewhere herein), winding the film around the rod to form an assembly (e.g., including a plurality of consecutive turns, or substantially concentric loops, of the film substantially concentric with the rod), and cutting substantially laterally through the assembly to form the coil or antenna. For example, a segment of the assembly may be cut from the assembly and this segment includes the coil or antenna wrapped around a segment of the rod which can optionally be removed. The cutting step can create any of the regular patterns described elsewhere herein on one or both (e.g., by slicing through the assembly with parallel spaced apart diamond wires) of the opposing sides of the coil or antenna. 
     The rod may be extended along an axis and have a cross-section orthogonal to the axis that has any suitable shape (e.g., circle, oval, or rounded rectangle (e.g., corresponding to the rounded rectangular shape of the interior region of the coil  3300 )). The rod may be composed of any suitable material. Suitable materials may include at least one of rigid polymers, crosslinked polymers, and epoxy. For example, the rod may include epoxy (e.g., the rod may be an epoxy rod). 
       FIGS.  61 - 64    schematically illustrate a method for making a coil or antenna of the present description. 
     A rod  410  and a film  420 , which may be a multilayer film and/or a film having at least one electrically conductive layer, are provided. In some embodiments, the rod  410  includes a slit  438  for receiving an end  434  of the film  420 . In some embodiments, the end  434  of the film  420  is placed into the slit  438  as schematically illustrated in  FIG.  61    and the film  420  is wound around the rod  410  as schematically illustrated in  FIG.  62    for a plurality of turns to form the assembly  401  schematically illustrated in  FIG.  63   . The film  420  can be wound around the rod  410  by turning the rod  410 , for example. Tension can be provided along an edge  436  while turning the rod  410 . The film  420  may correspond to any of the multilayer films described herein (e.g., multilayer film  202  or  402  or  502 ), for example. In some embodiments, the film  420  includes a plurality of alternating metal  10  and first adhesive layers  30 ; and a magnetically conductive second layer  20  disposed on and bonded to the plurality of alternating metal and first adhesive layers  10  and  30 , for example. The film  420  can be wound around the rod  410  in either orientation. For example, in embodiments where the film  420  includes a magnetically conductive or soft magnetic layer  20  closer to one outermost major surface of the film  420  than to the other outermost major surface, the film  420  can be wound with the layer  20  facing towards or facing away from the rod  410 . 
     In some embodiments, the film  420  is a multilayer film. In some embodiments, the assembly  401  includes a rod  410 , and a multilayer film  420  wound around a plurality of consecutive turns substantially concentric with the rod  410 . In some embodiments, a length L 3  of the rod  410  is greater than a lateral width W 3  of the multilayer film  420 . In some embodiments, the rod  410  extends beyond at least one lateral edge  421  of the multilayer film  420 . 
     In some embodiments, the method further includes cutting the assembly  401  into sections having a desired width for a coil.  FIG.  64    schematically illustrates cutting substantially laterally (e.g., in a plane  6496  having a normal making an angle with an axis of the rod of less than 45 degrees, or less than 30 degrees, or less than 20 degrees, or less than 10 degrees, or less than 5 degrees) through the assembly to form a separated portion of the assembly which includes a coil or antenna including a plurality of substantially concentric loops of a separated portion the multilayer film  420 . In some embodiments, the separated portion has a substantially uniform width (e.g., variations in the width less than 20%, or less than 10%, or less than 5% of an average width). In some embodiments, the separated portion of the assembly has a substantially uniform width substantially equal (e.g., with 20%, or with 10%, or with 5%) to the widths of layers (e.g., first 10, second 20 and third  30  layers) of the film  420 . 
     In some embodiments, a method of making a coil includes providing a rod  410 ; providing a multilayer film  420 ; winding the multilayer film around the rod to form an assembly  401  including the rod and a plurality of loops of the multilayer film substantially concentric with the rod; cutting substantially laterally through the assembly to form a separated portion  6400  of the assembly where the separated portion of the assembly includes the coil and the coil is or includes a plurality of substantially concentric loops of a separated portion the multilayer film. In some embodiments, winding the multilayer film around the rod  410  includes rotating the rod about an axis of the rod. In some embodiments, the separated portion of the assembly has opposite major surfaces and a substantially uniform (e.g., varying by less than 20%, or less than 10%, or less than 5%) width therebetween (e.g., the width W or W 1  depicted in  FIG.  1 B ). In some embodiments, the cutting step includes cutting or slicing substantially laterally through the assembly using a diamond wire saw. In some embodiments, cutting substantially laterally through the assembly includes using a plurality of spaced apart cutting wires to form a plurality of separated portions of the assembly where each separated portion of the assembly includes a coil in the plurality of coils and each coil includes a plurality of substantially concentric loops of a separated portion the multilayer film. 
     In some embodiments, the film  420  is a multilayer film corresponding to any multilayer film described elsewhere herein. For example, in some embodiments, the multilayer film  420  includes an electrically conductive first layer  10  and a magnetically conductive second layer  20  disposed on the first layer. In some embodiments, the first layer  10  is magnetically insulative. In some embodiments, the multilayer film further includes at least one electrically conductive third layer  17  disposed on the first layer  10 . In some embodiments, the at least one third layer  17  is magnetically insulative. In some embodiments, a relative permeability of the second layer  20  is at least 10 times, or at least 100 times a relative permeability of the first layer  10 . 
     In some embodiments, the multilayer film  420  includes a plurality of alternating electrically conductive  10  and first adhesive  30  layers and includes a second adhesive layer  41  including an outermost major surface  44  of the multilayer film. In some embodiments, the second adhesive layer  41  is thicker (e.g., at least by a factor of 2 or 4) than the first adhesive layer  30 . In some embodiments, the second adhesive layer  41  includes a composite portion  20  and opposing first and second adhesive portions  40  and  42  disposed on opposite major surfaces of the composite portion  20 . In some embodiments, the composite portion includes a magnetically conductive filler  43  dispersed in a binder. 
     In some embodiments, the film  420  is or includes an electrically conductive first layer  10 . In some embodiments, the film  420  is a multilayer film including an electrically conductive first layer  10  and a second layer (e.g.,  20  or  30  or  40  or  41  or  42 ) disposed on and bonded to the first layer. 
     In some embodiments, prior to winding the multilayer film, the multilayer film includes an uncured partially cured first adhesive layer (e.g.,  30  or  40  or  41  or  42 ) bonding the second layer to the first layer. In some embodiments, prior to winding the multilayer film, the multilayer film includes an uncured or partially cured second adhesive layer (e.g.,  41  or  42 ) that includes an outermost major surface  44  of the multilayer film. In some embodiments, the step of winding the multilayer film includes bonding adjacent loops in the plurality of loops through the second adhesive layer. In some embodiments, the method includes fully curing the first and second adhesive layers. For example, the first and second adhesive layers may be thermoset adhesive layers (e.g., thermoset epoxy) which can be thermally cured. In some embodiments, the fully curing step is carried out after the winding step and before the cutting step. In some embodiments, the fully curing step is carried out after the winding and cutting steps. 
     In some embodiments, the cutting or slicing step creates an edge surface  111  of each loop  110  of the separated portion of the multilayer film where the edge surface includes a regular pattern  120 . In some embodiments, the cutting step creates opposing edge surfaces of each loop of the separated portion of the multilayer film where each of the opposing edge surface includes a regular pattern (e.g.,  120  and  120   b , respectively). In some embodiments, a method of making a coil includes providing an assembly  401  including a rod  410  and a film  420  wound around a plurality of consecutive turns substantially concentric with the rod  410  where the film includes an electrically conductive first layer  10 ; and slicing substantially laterally through the assembly using at least one cutting wire to form a separated portion of the assembly where the separated portion of the assembly includes the coil, the coil includes a plurality of substantially concentric loops of a separated portion the film  420 , and the slicing step creates a first edge surface  111  of each loop  110  of the separated portion of the film including a first regular pattern  120 . In some embodiments, the first regular pattern  120  extends substantially along a same first direction and across substantially the entire coil. In some embodiments, the slicing step creates opposing first and second edge surfaces  111  and  111   b  of each loop of the separated portion of the film including respective first and second regular patterns  120  and  120   b . In some embodiments, each of the first and second regular patterns  120  and  120   b  extend substantially along a same first direction and across substantially the entire coil. 
     The regular pattern  120  and/or  120   b  can be any regular pattern described elsewhere herein for the coils or antennas of the present description. For example: In some embodiments, the regular pattern extends substantially along a same first direction and across substantially the entire coil. In some embodiments, the regular pattern extends along a first direction making an angle θ with a longitudinal direction of the loop where θ varies along the longitudinal direction of the loop. In some embodiments, the regular patterns of the edge surfaces of at least a plurality of adjacent loops of the separated portion of the multilayer film are substantially aligned with each other. In some embodiments, the regular pattern includes a pattern of substantially parallel grooves extending across at least a plurality of adjacent loops of the separated portion of the multilayer film. In some embodiments, the regular pattern has a first average pitch in a first region of the coil and a different second average pitch in a different second region of the coil. In some embodiments, a Fourier transform of the regular pattern has a peak at a first spatial frequency in a first region of the coil and a peak at a different second spatial frequency in a different second region of the coil. In some embodiments, in at least one first region of the coil, the coil includes a regular optical and topographical pattern along a first direction, and a regular optical, but not topographical, pattern along an orthogonal second direction. 
     In some embodiments, a method includes the step of providing the assembly  401 . In some embodiments, the step of providing the assembly  401  includes providing the rod  410 , providing the film  420 , and winding the film  420  around the rod  410  to form the assembly  401 . The method can further include inserting the end  434  of the film  420  into the slit  438  prior to winding the film  420 , and/or can further include heating the assembly to cure any uncured or partially cured adhesive layers. 
     In some embodiments, a wire saw  6494  is used to cut or slice through the assembly  401 . In some embodiments, the wire saw  6494  includes a plurality of spaced apart cutting wires  6495  to form a plurality of separated portions ( 6400   a  and  6400   b ) of the assembly  401 . In some embodiments, each separated portion includes a coil in the plurality of coils, and each coil includes a plurality of substantially concentric loops of a separated portion the film  420  (e.g., a multilayer film). In some embodiments, each separated portion of the assembly has a substantially uniform width. In some embodiments, the film  420  of the assembly  401  includes an electrically conductive first layer  10 . In some embodiments, each separated portion of the assembly includes a plurality of substantially concentric loops of a corresponding separated portion the film. 
     In some embodiments, the cutting wire(s) used to slice through the assembly is/are diamond wire(s). Diamond cutting wires can include a wire impregnated with diamond dust and have been used for slicing ceramics, for example.  FIG.  65    is a schematic illustration of a diamond wire  6595  including diamond particles  6597 . Suitable diamond wire saws are available from Crystal Systems Innovations (Salem, Mas.), for example. 
     The coils or antennas of the present description can be used for the transfer of information (e.g., digital or analogue data) or energy (e.g., for wireless recharging).  FIG.  66    is a schematic side view of a transceiver  303  including a coil or antenna  6100  and a first power source  6310  to energize the coil or antenna  6100 . The coil or antenna  6100  can be any coil or any antenna of the present description. 
     If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” can be understood to mean within 10 percent of the specified quantity, but also includes exactly the specified quantity. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, but also includes a value of exactly 1. 
     All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. 
     Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.