Patent Publication Number: US-11664565-B1

Title: Deformable conductive structures and methods for fabrication

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application Ser. No. 62/844,039 filed May 6, 2019 which is incorporated by reference. 
    
    
     BACKGROUND 
     Waveguides and transmission lines may be fabricated in various forms including microstrip, stripline, coplanar waveguide, coaxial cable, twinaxial cable, etc. The selection and configuration of materials used for conductors, dielectrics, etc., may determine the characteristic impedance of a waveguide or transmission line. 
     SUMMARY 
     A conductive assembly may include a deformable substrate disposed around an axis, and a deformable conductor arranged on the deformable substrate. The substrate may be arranged to form a channel along the axis, and the deformable conductor may be arranged on the deformable substrate to form a waveguide. The channel may be substantially enclosed. The deformable conductor may be a first deformable conductor, and the assembly may further include a second deformable conductor arranged on the deformable substrate. The first deformable conductor may be arranged substantially along the axis, and the second deformable conductor may be arranged as a reference conductor to form a transmission line with the first deformable conductor. The deformable substrate, the first deformable conductor, and the second deformable conductor may be arranged to form a microstrip transmission line. The first deformable conductor, and the second deformable conductor may be arranged to form a coaxial transmission line. The conductive assembly may further include a third deformable conductor arranged on the deformable substrate. The third deformable conductor may be arranged as a reference conductor to form a stripline with the first deformable conductor and the second deformable conductor. The third deformable conductor may be arranged substantially along the axis, and the deformable substrate, the first deformable conductor, the second deformable conductor and the third deformable conductor may be arranged to form a twinaxial transmission line. 
     A deformable transmission line may include a deformable substrate arranged in a substantially enclosed channel around an axis, a first deformable conductor arranged in a trace along the axis of the deformable substrate, and a second deformable conductor arranged on the deformable substrate to form a reference conductor for the first deformable conductor. The second deformable conductor may be arranged to form a microstrip with the first deformable conductor. The second deformable conductor may be arranged to substantially enclose the first deformable conductor, thereby forming a coaxial transmission line. The second deformable conductor may include an opening arranged to change the impedance of the transmission line in response to an object proximate the opening. This opening may also be used to allow coupling of the first conductor to objects on the exterior of the second conductor. 
     A method of fabricating a deformable conductive assembly may include forming a deformable conductor on a deformable substrate, and disposing the deformable substrate around an axis. The deformable substrate may be rolled around the axis. The deformable substrate may be folded around the axis. The deformable conductor may be a first deformable conductor, and the method may further include forming a second deformable conductor on the deformable substrate. The first deformable conductor may be formed on a first surface of the deformable substrate, and the second deformable conductor may be formed on the first surface of the deformable substrate. The first deformable conductor may be formed on a first surface of the deformable substrate, and the second deformable conductor may be formed on a second surface of the deformable substrate opposite the first surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures are not necessarily drawn to scale and elements of similar structures or functions may generally be represented by like reference numerals for illustrative purposes throughout the figures. The figures are only intended to facilitate the description of the various embodiments described herein. The figures do not describe every aspect of the teachings disclosed herein and do not limit the scope of the claims. To prevent the drawing from becoming obscured, not all of the components, connections, and the like may be shown, and not all of the components may have reference numbers. However, patterns of component configurations may be readily apparent from the drawings. 
         FIG.  1    is a perspective view of an embodiment of a conductive assembly according to this disclosure. 
         FIG.  2    is a perspective view of an embodiment of a conductive assembly according to this disclosure prior to shaping. 
         FIG.  3    is a side view of an embodiment of a conductive assembly according to this disclosure prior to shaping. 
         FIG.  4    is a side view of an embodiment of a conductive assembly according to this disclosure after shaping. 
         FIG.  5    is a perspective view of an embodiment of a conductive assembly according to this disclosure after shaping. 
         FIG.  6    is a side view of another embodiment of a conductive assembly according to this disclosure prior to shaping. 
         FIG.  7    is a side view of another embodiment of a conductive assembly according to this disclosure after shaping. 
         FIG.  8    is a side view of another embodiment of a conductive assembly according to this disclosure prior to shaping. 
         FIG.  9    is a side view of another embodiment of a conductive assembly according to this disclosure after shaping. 
         FIG.  10    is a side view of another embodiment of a conductive assembly according to this disclosure prior to shaping. 
         FIG.  11    is a side view of another embodiment of a conductive assembly according to this disclosure after shaping. 
         FIGS.  12  and  13    are graphs illustrating insertion loss and return loss, respectively, for an example embodiment of a coaxial transmission line fabricated in accordance with this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Some of the inventive principles of this patent disclosure relate to deformable conductive assemblies that may function, for example, as transmission lines and/or waveguides, and methods for fabricating such assemblies. 
       FIG.  1    is a perspective view of an embodiment of a conductive assembly according to this disclosure. The embodiment  100  of  FIG.  1    includes a deformable substrate  102  disposed around an axis  104 . Although the substrate  102  is shown in a partially curved configuration around the axis  104 , in other embodiments, the substrate  102  may have any cross-sectional shape including square, triangular, U-shaped, stacked with one or more folds, etc., and may be disposed around the axis  104  to any extent, either partially as shown in  FIG.  1   , or in a substantially or completely enclosed configuration. 
     The embodiment  100  may include a deformable conductor  106  on the inside of the deformable substrate  102 . The deformable conductor  106  is illustrated as a trace arranged along the axis  104 , but the deformable conductor  106  may be arranged in any pattern. Additionally, or alternatively, the embodiment  100  may include a second deformable conductor  108  on the outside of the deformable substrate  102 . The second deformable conductor is illustrated as an area of conductor covering the outside surface of the deformable substrate  102 , but the second deformable conductor  108  may be arranged in any pattern. In other embodiments, any number of deformable conductors may be included on either side of the substrate. 
     In the embodiment  100  illustrated in  FIG.  1   , the first and second deformable conductors  106  and  108  may be used as essentially a microstrip transmission line along the axis  104  with the deformable substrate  102  functioning as a dielectric. Other embodiments may be modified to form various waveguides, transmission lines, and/or other conductive structures. For example, the deformable substrate  102  and second deformable conductor  108  may be extended to create a substantially enclosed channel around the axis  104 , thereby forming a coaxial transmission line. As another example, the deformable substrate  102  and second deformable conductor  108  may be extended to form a substantially enclosed channel around the axis  104 , but the first deformable conductor  106  may be omitted, thereby enabling the second deformable conductor  108  to form a waveguide. Alternatively, the second deformable conductor  108  may be omitted from the outside of the substrate  102 , and the first deformable conductor  106  may be extended to cover substantially the entire inside of the substrate  102 , thereby forming a waveguide. 
     In some embodiments, the deformable substrate  102  may be implemented with any suitable material or combination of materials that may provide deformable characteristics which, in various embodiments, may be characterized as: soft, stretchable, resilient, flexible, compressible, pliable, elastic, and/or the like. In various embodiments, the substrate  102 , or portions thereof, may or may not spontaneously return to a neutral state when various forces associated with physical manipulation are removed. 
     Some examples of materials that may be used for the deformable substrate  102  body include any flexible and/or stretchable material such as solid and/or foam polymers including neoprene, ethylene propylene diene monomer (EPDM), polydimethylsiloxane (PDMS), polyethylene, polyurethane including thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), epoxies and epoxy based materials, nitrile rubber, silicone, fiberglass, natural rubber, as well as other natural materials such as sponges, cork and/or wood, etc., woven and/or nonwoven fabrics, and any hybrid combinations such as laminations or composites thereof. The substrate  102  may be implemented as a single component, or may include multiple components arranged in any configuration around the axis. 
     Although the inventive principles are not limited to any specific materials for use as the deformable conductors, some examples include, but are not limited to, deformable conductors such as gallium indium alloy gels, some examples of which are disclosed in U.S. Patent Application Publication No. 2018/0247727 published on Aug. 30, 2018 which is incorporated by reference. Other suitable conductive materials may include any compositions in liquid, gel and/or elastic form featuring conductive metals including gold, nickel, silver, platinum, copper, etc.; semiconductors based on silicon, gallium, germanium, antimony, arsenic, boron, carbon, selenium, sulfur, tellurium, etc., semiconducting compounds including gallium arsenide, indium antimonide, and oxides of many metals; organic semiconductors; and conductive nonmetallic substances such as graphite. Other examples include gels based on graphite or other allotropes of carbon, ionic compounds or other gels. 
     In some embodiments, a deformable conductor referred to as being on a substrate may also refer to a conductor that may be partially or completely disposed within a substrate. 
     The materials used for the substrate and one or more conductors, as well as the arrangement and sizes of the components may be selected to provide any desired electrical and/or mechanical characteristics. For example, in some embodiments, the deformable substrate may be implemented with one or more materials that may have a dielectric property suitable for use in a transmission line. The thickness of the substrate may then be selected to provide a specific characteristic impedance Z 0 , which may in turn be related to the capacitance and inductance of the geometry and material properties of the conductor(s) and dielectric(s). Likewise, the material or materials used for the deformable conductors may be selected to provide a specific DC resistance. 
       FIGS.  2 - 5    illustrate an example embodiment of a coaxial transmission line assembly according to this disclosure. The embodiment  110  illustrated in  FIGS.  2 - 5    may include a deformable substrate  112  formed, for example, from a sheet of stretchable polymer.  FIG.  2    is a perspective view of the embodiment  110  prior to shaping.  FIG.  3    is a side view of the embodiment  110  in which the axis around which the substrate  112  will be disposed is perpendicular to the plane of the drawing.  FIG.  4    is a side view if the assembly after the substrate has been rolled into its final configuration.  FIG.  5    is a perspective view of the final assembly after the substrate has been rolled into its final configuration. 
     Referring to  FIGS.  2  and  3   , a trace  114  of deformable conductor may be deposited on a first side of the substrate  112 , while the other side of the substrate  112  may be essentially covered with a layer  116  of deformable conductor. The conductors  114  and  116  may be implemented, for example, with a conductive gel. In some embodiments, a pattern of dots, grids, etc. may be used to hold the gel in place. 
     Referring to  FIGS.  4  and  5   , the substrate  112  may be rolled to form a coaxial transmission line with the first conductor  114  forming a central or signal conductor through the center of the assembly, and the second conductor  116  forming a ground or reference conductor around the signal conductor. The substrate  112  may function as a dielectric between the two conductors. 
     Though not illustrated in  FIGS.  2 - 5   , one or more layers of encapsulant may be included to partially or fully cover either or both of the conductors  114  and  116 . An encapsulant may perform one or more functions such as protecting a conductor from exposure to air (which may cause oxidation of the conductor), dirt, moisture, and/or other contaminants, and protecting a conductor from mechanical wear or impact. An encapsulant may also function as an adhesive to hold the assembly together after rolling. An encapsulant may further be used to fill interstitial spaces, such as space  118 , which may be formed in the assembly during the rolling process. Examples of materials suitable for encapsulant  118  include silicone based materials such as PDMS, urethanes, epoxies, polyesters, polyamides, varnishes, and any other material that may provide a protective coating and/or help hold the assembly together. 
     In some embodiments, one or more electric and/or mechanical connections  120  may be formed between overlapping layers of the substrate  112  and/or conductor  116  and may perform any number of functions. For example, connections  120  may mechanically tie overlapping layers of the substrate  112  together to hold the assembly together, as an alternative to, or in addition to, an adhesive encapsulant. As another example, the connections may electrically connect the overlapping layers of conductor  116  to provide a more complete electrical continuity around the circumference of the transmission line. The one or more electric and/or mechanical connections  120  may be formed in any pattern around and/or along the axis of the assembly. 
     Examples of structures that may be used for the one or more electric and/or mechanical connections  120  include rivets, screws, pins, stiches (conductive and/or nonconductive), etc. In some embodiments, electric connections may be formed by forming one or more vias in the substrate  112  and filling the vias with a conductive material such as a conductive gel, for example, using any of the techniques disclosed in U.S. Patent Application Publication No. 2020/0066628 published on Feb. 27, 2020 which is incorporated by reference. 
     Electrical and/or mechanical connections may be made to the transmission line in any suitable manner. For example, bonding with adhesives, thermal and/or ultrasonic welding, etc. One or more techniques from U.S. Patent Application Publication No. 2020/0066628 may also be used, for example, to provide electrical connections to one or more of the deformable conductors. 
     In some embodiments, one or more openings may be formed in the outer deformable conductor  116  and arranged, for example, to change the impedance of the transmission line in response to an object proximate the opening. Thus, the assembly  110  may be used for example, to sense the presence of a users hand on the transmission line. 
       FIGS.  6  and  7    illustrate an example embodiment of a deformable microstrip transmission line according to this disclosure. The embodiment  122  of  FIGS.  6  and  7    may include a deformable substrate  124  formed, for example, from a sheet of stretchable polymer.  FIG.  6    is a side view of the embodiment  122  in which the axis around which the substrate  124  will be disposed is perpendicular to the plane of the drawing.  FIG.  7    is a side view of the assembly after the substrate has been folded into its final configuration. 
     Referring to  FIG.  6   , a trace  126  of deformable conductor may be formed on a first side of the substrate  124 , while two traces  128  and  130  of deformable conductor may be formed on the other side of the substrate  124 . The conductors  126 ,  128  and  130  may be implemented, for example, with a conductive gel. In some embodiments, a pattern of dots, grids, etc. may be used to hold the gel in place. 
     Referring to  FIG.  7   , the substrate  124  may be folded to form a stripline transmission line with the first conductor  126  forming a central or signal conductor through the center of the assembly, and the second and third conductors  128  and  130  forming ground or reference conductors on either side of the signal conductor. The substrate  124  may function as a dielectric between the conductors. 
     Any of the materials and/or techniques described above may be used to implement the embodiment  122  illustrated in  FIGS.  6  and  7   . 
       FIGS.  8  and  9    illustrate another example embodiment of a deformable transmission line according to this disclosure. In the embodiment illustrated in  FIGS.  8  and  9   , a deformable signal conductor  134  and a deformable reference conductor  136  may be formed on the same side of a deformable substrate  138 . The substrate  138  may then be rolled to form a transmission line having a cross section similar to a microstrip with a curved reference (ground) conductor. 
       FIGS.  10  and  11    illustrate another example embodiment of a deformable transmission line according to this disclosure. In the embodiment illustrated in  FIGS.  10  and  11   , a deformable signal conductor  142  and a deformable reference conductor  144  may be formed on the same side of a deformable substrate  146 . The substrate  146  may then be rolled to form a coaxial transmission line. 
     Any of the materials and/or techniques described above may be used to implement the embodiments illustrated in  FIGS.  8 - 11   . 
       FIGS.  12  and  13    are graphs illustrating insertion loss and return loss, respectively, for an example embodiment of a coaxial transmission line fabricated in accordance with this disclosure. The graphs illustrated in  FIGS.  12  and  13    are for purposes of illustrating general trends that may be observed according to the principles of this disclosure, but may not represent actual data from a physical embodiment. 
       FIG.  12    illustrates examples of insertion loss on a logarithmic (dB) vertical scale versus frequency on a linear horizontal scale for a section of coaxial transmission line subjected to no stretch (solid line), about 10 percent stretch (dashed line) and about 30 percent stretch (dotted line). 
       FIG.  13    illustrates examples of return loss on a logarithmic (dB) vertical scale versus frequency on a linear horizontal scale for a section of coaxial transmission line subjected to no stretch (solid line), about 10 percent stretch (dashed line) and about 30 percent stretch (dotted line). 
     As is apparent from the graphs of  FIGS.  12  and  13   , a deformable conductive structure according to this disclosure may be used in multiple modes, for example, for transmitting signals and/or power, and/or for sensing a deformation of the conductive structure. For example, a sensing circuit may be coupled to a deformable transmission line and configured to sense a stretching of the transmission line based on measuring the insertion loss, return loss, characteristic impedance, etc. 
     The terms “first”, “second”, etc., as used herein may be used for convenience of reference, for example, to distinguish between different elements, but the use of “first”, “second”, etc., for an element does not necessarily imply the presence of another element. 
     Since the inventive principles of this patent disclosure can be modified in arrangement and detail without departing from the inventive concepts, such changes and modifications are considered to fall within the scope of the following claims.