Conductive and adhesive liquid metal copper paste

Abstract

Embodiments of a liquid metal paste for coupling conductive components of circuits formed in or on rigid, flexible, and stretchable substrates are described. In one example, a liquid metal paste includes liquid metal. The liquid metal paste further includes copper elements mixed with the liquid metal to form a conductive mixture. In another example, the liquid metal paste further includes an elastomer material mixed with the liquid metal to form a conductive and adhesive mixture.

Description

Attorney Docket: 222204-2960 CONDUCTIVE AND ADHESIVE LIQUID METAL COPPER PASTE CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Application Serial No.63 / 535,946, filed August 31, 2023, titled “CONDUCTIVE AND ADHESIVE LIQUID METAL COPPER PASTE,” the entire contents of which are hereby incorporated herein by reference. BACKGROUND

[0002] Flexible circuits are an emerging technology with promising applications in modern consumer electronics, wearable health-monitoring devices, and soft robotics. Traditionally, electronic components have been soldered to rigid printed circuit boards (PCBs) either manually or through the use of automated systems such as reflow ovens and wave solder machines. In recent years, electrically conductive adhesives (ECAs) have been more widely used as interconnects in deformable systems. Compliant, conductive adhesives are critical in flexible and hybrid electronics for the integration of rigid integrated circuits (ICs) with flexible circuits. SUMMARY

[0003] Described herein are embodiments of an electrically and thermally conductive liquid metal (LM) paste. The LM paste may be embodied in some examples as a LM copper (Cu) paste having copper elements mixed in a eutectic gallium-indium liquid metal. The LM paste may include an elastomer material in some cases to add adhesive characteristics to the LM paste. The LM paste can be used to couple conductive components of circuits formed in or on at least one of a rigid, flexible, or stretchable substrate.

[0004] Aspects and advantages of embodiments of the present disclosure will be set forth in part in the following description or can be learned from the description or through practice of the embodiments. Other aspects and advantages of embodiments of the present disclosure will become better understood with reference to the appended claims and the accompanying drawings, all of which are incorporated in and constitute a part of this specification. The drawings illustrate example embodiments of the present disclosure and, together with the description, serve to explain the related concepts of the present disclosure.Attorney Docket: 222204-2960

[0005] According to one example embodiment, a liquid metal paste includes liquid metal. The liquid metal paste further includes copper elements mixed with the liquid metal to form a conductive mixture. In another example, the liquid metal paste further includes an elastomer material mixed with the liquid metal to form a conductive and adhesive mixture.

[0006] According to another example embodiment, a liquid metal adhesive includes liquid metal. The liquid metal adhesive further includes conductive elements mixed with the liquid metal. The liquid metal adhesive further includes an elastomer material mixed with the liquid metal and the conductive elements to form a conductive and adhesive mixture.

[0007] According to another example embodiment, a device includes a substrate, a liquid metal adhesive coupled to the substrate, and a conductive component coupled to the liquid metal adhesive. The liquid metal adhesive includes liquid metal. The liquid metal adhesive further includes conductive elements mixed with the liquid metal. The liquid metal adhesive further includes an elastomer material mixed with the liquid metal and the conductive elements to form a conductive and adhesive mixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Many aspects of the present disclosure can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, with emphasis instead being placed upon clearly illustrating the concepts of the disclosure. Moreover, repeated use of reference characters or numerals in the figures is intended to represent the same or analogous features, elements, or operations across different figures. Repeated description of such repeated reference characters or numerals is omitted for brevity.

[0009] FIG. 1A illustrates a cross-sectional view of an example device according to various aspects and embodiments of the present disclosure.

[0010] FIG.1B illustrates a top view of the example device of FIG. 1A according to various aspects and embodiments of the present disclosure.

[0011] FIG. 2A illustrates a cross-sectional view of another example device according to various aspects and embodiments of the present disclosure.

[0012] FIG.2B illustrates a top view of the example device of FIG. 2A according to various aspects and embodiments of the present disclosure.

[0013] FIG. 3A illustrates a cross-sectional view of another example device according to various aspects and embodiments of the present disclosure.Attorney Docket: 222204-2960

[0014] FIG.3B illustrates a top view of the example device of FIG. 3A according to various aspects and embodiments of the present disclosure.

[0015] FIG. 4A illustrates a cross-sectional view of another example device according to various aspects and embodiments of the present disclosure.

[0016] FIG.4B illustrates a top view of the example device of FIG. 4A according to various aspects and embodiments of the present disclosure.

[0017] FIG. 5A illustrates a cross-sectional view of another example device according to various aspects and embodiments of the present disclosure.

[0018] FIG.5B illustrates a top view of the example device of FIG. 5A according to various aspects and embodiments of the present disclosure.

[0019] FIG.6A illustrates a plot of example x-ray diffraction results showing the interaction of gallium-indium liquid metal with iron (Fe) microparticles according to various aspects and embodiments of the present disclosure.

[0020] FIG. 6B illustrates a plot of example x-ray diffraction results showing the interaction of gallium-indium liquid metal with copper (Cu) microparticles according to various aspects and embodiments of the present disclosure.

[0021] FIG. 6C illustrates a plot of example x-ray diffraction results showing the interaction of gallium-indium liquid metal with nickel (Ni) microparticles and silver (Ag) microparticles according to various aspects and embodiments of the present disclosure.

[0022] FIG.7A illustrates a diagram of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.

[0023] FIG. 7B illustrates another diagram of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.

[0024] FIG. 7C illustrates another diagram of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.

[0025] FIG. 7D illustrates another diagram of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.Attorney Docket: 222204-2960

[0026] FIG. 7E illustrates a plot of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.

[0027] FIG.7F illustrates another plot of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.

[0028] FIG.7G illustrates another plot of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure. DETAILED DESCRIPTION

[0029] Flexible circuits are an emerging technology with promising applications in modern consumer electronics, wearable health-monitoring devices, and soft robotics. Traditionally, electronic components have been soldered to rigid printed circuit boards (PCBs) either manually or through the use of automated systems such as reflow ovens and wave solder machines. However, utilizing these techniques to attach components to flexible substrates such as flexible polymeric substrates is a challenge, as flexible polymeric substrates and circuits cannot withstand the high temperatures used in traditional electronic processing. For example, typical tin-lead solders have melting temperatures that are often in excess of the glass transition temperature of polymeric substrates commonly used for flexible circuits, which can lead to thermal expansion or damage.

[0030] Low-temperature solders, which incorporate low-melting point metals such as bismuth and indium, can be used to prevent damage to substrates. However, a vast majority of solder alloys, regardless of their melting temperature, tend to be brittle in their solid state. Consequently, bending strains in flexible systems can cause brittle fracture or delamination of the solder, which demands extra design considerations to allow for deformation with integrated components. Such considerations can severely limit the types of geometries that flexible circuits can conform to. As a result, there is an increasing need for materials that have high flexibility, exceptional electrical conductivity, strong adhesion, and processibility at low temperature, as these properties are essential to component integration in flexible electronic systems.

[0031] In recent years, polymer-based electrically conductive adhesives (ECAs) have been more widely used as interconnects in deformable systems. However, their fabrication andAttorney Docket: 222204-2960 integration into these systems has proven to be difficult. For example, intrinsically conductive polymers have been used as ECAs, but these typically have lower values of conductivity (e.g., 102< ı < 103S m-1) and poor adhesion strength (e.g., < 1 kPa in shear), and various chemical processes are required to enhance these properties. Another method to enhance electrical conductivity and adhesion is to put fillers such as conductive ceramics, carbon-based fillers, and metals into naturally adhesive polymers such as epoxies. However, most epoxies do not have the desired mechanical properties to function as a flexible interconnect, as they are typically rigid (E ^ 1 GPa) and thus do not easily interface with flexible substrates. Additionally, rigid fillers can further increase the modulus of the composite system, which is highly detrimental in deformable applications. It therefore remains a challenge to create solder-like materials with optimal combinations of flexibility, conductivity, and adhesion for integrated hybrid systems such as flexible electronics with rigid components.

[0032] To address the aforementioned problems associated with incorporating electrical components into flexible and / or stretchable substrates in general and with respect to existing ECA approaches, embodiments described herein include an electrically and thermally conductive liquid metal (LM) paste and methods for fabricating the same. The LM paste may be embodied in some examples as a LM copper paste having copper elements (e.g., particles, flakes) mixed in a eutectic gallium-indium liquid metal. The LM utilized in one example is a eutectic alloy of 75% gallium (Ga) and 25% indium (In) known as “eGaIn,” although other ratios may be utilized. Copper elements having one or more defined sizes (e.g., uniform or nonuniform in size) are mixed with the LM in various examples at different mass ratios up to a defied percentage to form semi-solid mixtures. In one example, copper elements of 500 nm size are mixed with the LM at different mass ratios up to 30% to form semi-solid mixtures, although other particle sizes and / or mass ratios may be relied upon in some cases.

[0033] Different compositions of the LM paste are described in embodiments herein. One example has a 4% copper loading, and another example has a 7% copper loading. However, copper loadings of less than 4% and greater than 7% may be relied upon in some cases. The LM pastes described herein may be applied on a surface in a particular pattern using a stencil mask to form traces in some cases or by using an extrusion application or a three-dimensional (3D) printing application in other examples. The LM pastes may be used to form a different component in some examples such as, for instance, a contact pad, among other components. In one example, LM paste traces formed on a surface may be encapsulated using a thin polyurethane coating. A conductiveAttorney Docket: 222204-2960 component (e.g., electrical, electromechanical, electromagnetic, optical) may also be coupled to any or all of the LM paste traces in some examples.

[0034] The LM pastes described in some examples can be embodied and implemented as an adhesive interconnect component (e.g., a trace, contact pad) that is electrically and / or thermally conductive and operable to couple integrated conductive components formed in or on at least one of a rigid, flexible, or stretchable substrate. The LM pastes can be combined (e.g., mixed) with one or more elastomers such as, for instance, silicones and polyurethanes to impart adhesion characteristics in the paste. When printed or cast on a surface these LM paste embodiments can be adhesive to a surface after curing while also being thermally and / or electrically conductive. An LM-4%Cu paste is mixed in one example with a silicone elastomer and applied to a surface in a certain pattern using a stencil mask, although an extrusion or 3D printing application may be utilized to apply an LM paste having a different mass ratio in some cases.

[0035] The LM pastes described in some examples for electronic applications can also be formulated with other low melting point alloys including, but not limited to, a eutectic alloy of gallium (Ga), indium (In), and tin (Sn), an alloy of bismuth (Bi), indium (In), and tin (Sn), an alloy of bismuth (Bi), lead (Pb), and tin (Sn), an alloy of lead (Pb), tin (Sn), and cadmium (Cd). In other cases, a different combination of gallium, indium, tin, bismuth, lead, cadmium, and / or another metal may be used to form any LM paste described herein. Additionally, the melting and crystallization point of such alloys could be modified by adding other metals in some cases.

[0036] One LM paste embodiment described herein can be created by doping any of the aforementioned alloys with micro or nanoparticles of other metals such as, for instance, iron (Fe), zinc (Zn), nickel (Ni), silver (Ag), gold (Au), titanium (Ti), platinum (Pt), copper (Cu). In another example, an LM paste can be created by initially fabricating elements of a low melting point alloy and fusing it with one or more other metal elements listed above at room temperature or elevated temperatures to form intermetallics (e.g., intermetallic compounds defined as solid phases with metallic or semi-metallic elements having an ordered structure and / or a well-defined, fixed stoichiometry).

[0037] The LM pastes of the present disclosure provide numerous technical advantages and benefits. For example, in the uncured state, an LM paste can be stenciled or deposited through extrusion or 3D printing, allowing for versatility in manufacturing techniques and a high degree of precision when needed. Curing can take place between room temperature and, for instance, 100 °C to allow for low-temperature processing for heat-sensitive components. The rheologicalAttorney Docket: 222204-2960 behavior (e.g., flow properties) of the LM pastes can be modified in different examples by the choice of metal elements that either react / interact to form different alloys or do not have any chemical reaction / interaction and merely form mixtures. The electrical and / or thermal conductivity of the LM pastes can be custom defined to achieve a certain goal in different examples by modifying their material content or composition, and / or by altering the fabrication process used to form them. Some example LM pastes described herein that are formed with low melting point alloys can be printed as particles or traces directly onto or into at least one of a rigid, flexible, or stretchable circuit board for electrical connections of conductive components.

[0038] Turning now to the figures, FIG. 1A illustrates a cross-sectional view of an example device 100 according to various aspects and embodiments of the present disclosure. FIG. 1B illustrates a top view of the example device 100 according to various aspects and embodiments of the present disclosure. The device 100 includes a substrate 110 and a liquid metal (LM) paste 120 formed on the substrate 110, although the LM paste 120 can be embodied and implemented independent of the substrate 110 in some cases. The LM paste 120 can be embodied and implemented as an electrically and thermally conductive LM paste or adhesive in various examples. The LM paste 120 can also be embodied and implemented as an inherently conductive and adhesive semi-solid or solid structure that couples conductive components formed on or in the substrate 110 in other examples. Some example embodiments and implementations of the LM paste 120 with or without the substrate 110 include, but are not limited to, an electrical and thermal contact, interconnect, trace, or other electrically and thermally conductive components.

[0039] The substrate 110 can be embodied as a rigid substrate in one example, or as at least one of a flexible or stretchable substrate in another. The LM paste 120 includes liquid metal having conductive elements (e.g., particles, flakes) and an elastomer material mixed with the liquid metal to form a conductive and adhesive mixture. The elastomer material may be omitted from the LM paste 120 in another example. The LM paste 120 can be deposited or otherwise at least partially formed on a surface of the substrate 110 in some examples or at least partially integrated into the substrate 110 in other examples.

[0040] The liquid metal in the LM paste 120 can be embodied as a eutectic gallium-indium liquid metal in one example. In other examples, the liquid metal in the LM paste 120 can be formed using one or more liquid metals that can include, but are not limited to, gallium, indium, tin, bismuth, lead, or cadmium liquid metal. The liquid metal in the LM paste 120 can be embodied as a eutectic gallium-indium-tin liquid metal in one example. The liquid metal in the LM paste 120Attorney Docket: 222204-2960 can be embodied as a bismuth-indium-tin liquid metal in another example, as a bismuth-lead-tin liquid metal in yet another example, or as a lead-tin-cadmium liquid metal in still another example. In the example depicted in FIGS.1A and 1B, the liquid metal in the LM paste 120 is embodied as a eutectic gallium-indium liquid metal having a gallium to indium mass ratio of 3:1, although another mass ratio may be relied upon in some cases.

[0041] The conductive elements in the LM paste 120 can be embodied as copper elements in one example, although other metal elements may be used in place of or in addition to the copper elements in other cases. For example, the conductive elements in the LM paste 120 can be embodied as at least one of copper, iron, zinc, nickel, silver, gold, titanium, platinum, or another conductive element. The elastomer material in the LM paste 120 can be embodied as polyurethane material in one example or as a silicone material in another.

[0042] The LM paste 120 can include up to approximately 30 percent (%) by mass (mass%) or by volume (vol%) of the conductive elements in various examples, although a percentage greater than 30% may be relied upon in some examples. In one example the LM paste 120 can include approximately 4% (e.g., mass% or vol%) of the conductive elements. The LM paste 120 can include approximately 7% (e.g., mass% or vol%) of the conductive elements in another example. In a different example the LM paste 120 can include a liquid metal with a 4% loading (e.g., mass% or vol%) of copper mixed at approximately 70% loading (e.g., mass% or vol%) into silicone material, although a percentage loading greater or less than 70% may be relied upon in some cases. The elastomer material mixed in the liquid metal of the LM paste 120 provides the LM paste 120 with intrinsic adhesive properties in addition to the conductive properties provided by the conductive elements. The conductive elements may be formed into various shapes and sizes. For instance, any or all of the conductive elements may be formed as a nano-sized conductive particle or flake, a micron-sized conductive particle or flake, or a conductive particle or flake formed to another size. In one example at least one of the conductive elements is approximately 500 nanometers in size.

[0043] In an uncured state the LM paste 120 may be embodied and applied (e.g., directly) as an ink to the substrate 110 shown in FIG. 1. The LM paste 120 may be embodied as a stencil ink that can be applied to the substrate 110 at room temperature (e.g., approximately 20-22°C) in some examples using a stenciling process involving the use of a stenciling mask. The LM paste 120 may also be embodied as dispensable 3D printer ink that can be applied to the substrate 110 at room temperature in other examples using a 3D printing process involving the use of a 3D printer. InAttorney Docket: 222204-2960 still other examples the LM paste 120 may be embodied as dispensable ink that can be applied to the substrate 110 at room temperature using an extrusion process involving the use of an extruder. The LM paste 120 can be applied to the substrate 110 according to various widths W. Some example applications of the LM paste 120 on the substrate 110 include widths W ranging between approximately 50 micrometers (μm) to approximately 250 μm.

[0044] In an uncured state the LM paste 120 can form a conductive and adhesive semi-solid mixture. For instance, the conductive and adhesive mixture formed by all the components of the LM paste 120 can take on a semi-solid form in an uncured state. In a cured state the LM paste 120 can form a conductive and adhesive semi-solid mixture in some examples or a conductive and adhesive solid mixture in other examples, depending on the composition elected for the LM paste 120. For example, the conductive and adhesive mixture formed by all the components of the LM paste 120 can take on a semi-solid or solid form in a cured state, depending on the composition elected for the LM paste 120. The curing rate for the LM paste 120 (e.g., time for transition from a semi-solid uncured state to a semi-solid or solid cured state) can also vary depending on the composition elected for the LM paste 120.

[0045] FIG.2A illustrates a cross-sectional view of another example device 200 according to various aspects and embodiments of the present disclosure. FIG. 2B illustrates a top view of the example device 200 according to various aspects and embodiments of the present disclosure. The device 200 is an example alternative embodiment of the device 100 described herein and illustrated in FIGS.1A and 1B. The device 200 includes one or more conductive components 230 coupled to the LM paste 120 and to the substrate 110 by way of the LM paste 120. The conductive component 230 can also be at least partially positioned in or integrated into the substrate 110 and coupled to the LM paste 120 in some examples. Example conductive components 230 can include, but are not limited to, an electrode, a light emitting diode (LED), a Hall effect sensor, a passive component, a resistor, a capacitor, an inductor, a transformer, an integrated circuit (IC), or another conductive component.

[0046] FIG.3A illustrates a cross-sectional view of another example device 300 according to various aspects and embodiments of the present disclosure. FIG. 3B illustrates a top view of the example device 300 according to various aspects and embodiments of the present disclosure. The device 300 is an example alternative embodiment of the device 200 described herein and illustrated in FIGS. 2A and 2B. The device 300 includes conductive components 230a, 230b coupled to the LM paste 120 and to the substrate 110 by way of the LM paste 120. One or both of the conductiveAttorney Docket: 222204-2960 components 230a, 230b can also be at least partially positioned in or integrated into the substrate 110 and coupled to the LM paste 120 in some examples. Example conductive components 230a, 230b can include, but are not limited to, an electrode, a light emitting diode (LED), a Hall effect sensor, a passive component, a resistor, a capacitor, an inductor, a transformer, an integrated circuit (IC), or another conductive component.

[0047] FIG.4A illustrates a cross-sectional view of another example device 400 according to various aspects and embodiments of the present disclosure. FIG. 4B illustrates a top view of the example device 400 according to various aspects and embodiments of the present disclosure. The device 400 is an example alternative embodiment of the device 300 described herein and illustrated in FIGS.3A and 3B. The device 400 includes a protective layer 440 encapsulating at least a portion of at least one of the substrate 110, the LM paste 120, or one or more of the conductive components 230a, 230b. The protective layer 440 can be embodied as a polyurethane coating in some examples. The protective layer 440 can also at least partially couple at least a portion of at least one of the LM paste 120 or one or more of the conductive components 230a, 230b to the substrate 110.

[0048] FIG.5A illustrates a cross-sectional view of another example device 500 according to various aspects and embodiments of the present disclosure. FIG. 5B illustrates a top view of the example device 500 according to various aspects and embodiments of the present disclosure. The device 500 is an example alternative embodiment of the device 400 described herein and illustrated in FIGS. 4A and 4B. The device 500 includes liquid metal (LM) pastes 520a, 520b, 520c, 520d formed on the substrate 110. The device 500 further includes conductive components 530a, 530b, 530c, 530d, 530e, 530f, 530g, 530h coupled to the LM pastes 520a, 520b, 520c, 520d as shown in FIGS.5A and 5B, although other patterns and circuits including such pastes and components may be formed in other examples.

[0049] The conductive components 530a, 530b are coupled to the LM paste 520a and to the substrate 110 by way of the LM paste 520a. The conductive components 530c, 530d are coupled to the LM paste 520b and to the substrate 110 by way of the LM paste 520b. The conductive components 530e, 530f are coupled to the LM paste 520c and to the substrate 110 by way of the LM paste 520c. The conductive components 530g, 530h are coupled to the LM paste 520d and to the substrate 110 by way of the LM paste 520d. Any or all of the conductive components 530a, 530b, 530c, 530d, 530e, 530f, 530g, 530h can also be at least partially positioned in or integrated into the substrate 110 and coupled to their corresponding LM paste 520a, 520b, 520c, 520d in some examples. Example conductive components 530a, 530b, 530c, 530d, 530e, 530f, 530g, 530hAttorney Docket: 222204-2960 can include, but are not limited to, an electrode, a light emitting diode (LED), a Hall effect sensor, a passive component, a resistor, a capacitor, an inductor, a transformer, an integrated circuit (IC), or another conductive component.

[0050] The LM pastes 520a, 520b are spaced apart from one another at a distance D1, the LM pastes 520b, 520c are spaced apart from one another at a distance D2, and the LM pastes 520c, 520d are spaced apart from one another at a distance D3. The distances D1, D2, D3can be equal to one another in some examples and in other examples at least one of the distances D1, D2, D3can be different from at least one of the other distances D1, D2, D3. Some example applications of the LM pastes 520a, 520b, 520c, 520d on the substrate 110 include distances D1, D2, D3 that each range between approximately 100 μm to approximately 1 millimeter (mm).

[0051] The device 500 further includes the protective layer 440 encapsulating at least a portion of at least one of the substrate 110, one or more of the LM pastes 520a, 520b, 520c, 520d, or one or more of the conductive components 530a, 530b, 530c, 530d, 530e, 530f, 530g, 530h. The protective layer 440 can also at least partially couple at least a portion of at least one of the LM pastes 520a, 520b, 520c, 520d or one or more of the conductive components 530a, 530b, 530c, 530d, 530e, 530f, 530g, 530h to the substrate 110.

[0052] FIG. 6A illustrates a plot 600a of example x-ray diffraction results showing the interaction of gallium-indium liquid metal with iron (Fe) microparticles according to various aspects and embodiments of the present disclosure. FIG.6B illustrates a plot 600b of example x- ray diffraction results showing the interaction of gallium-indium liquid metal with copper (Cu) microparticles according to various aspects and embodiments of the present disclosure. FIG. 6C illustrates a plot 600c of example x-ray diffraction results showing the interaction of gallium- indium liquid metal with nickel (Ni) microparticles and silver (Ag) microparticles according to various aspects and embodiments of the present disclosure.

[0053] FIGS. 7A, 7B, 7C, and 7D illustrate diagrams 700a, 700b, 700c, 700d, respectively, of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure. FIGS. 7E, 7F, and 7G illustrate plots 700e, 700f, 700g, respectively, of example thermodynamic and kinetic simulations of a multiphase solid-liquid system containing gallium-indium liquid metal and solid copper microparticles according to various aspects and embodiments of the present disclosure.Attorney Docket: 222204-2960

[0054] Disjunctive language, such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is to be understood with the context as used in general to present that an item, term, or the like, can be either X, Y, or Z, or any combination thereof (e.g., X, Y, and / or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to be each present. As referenced herein in the context of quantity, the terms “a” or “an” are intended to mean “at least one” and are not intended to imply “one and only one.”

[0055] As referred to herein, the terms “include,” “includes,” and “including” are intended to be inclusive in a manner similar to the term “comprising.” As referenced herein, the terms “or” and “and / or” are generally intended to be inclusive, that is (i.e.), “A or B” or “A and / or B” are each intended to mean “A or B or both.” As referred to herein, the terms “first,” “second,” “third,” and so on, can be used interchangeably to distinguish one component or entity from another and are not intended to signify location, functionality, or importance of the individual components or entities. As referenced herein, the terms “couple,” “couples,” “coupled,” and / or “coupling” refer to chemical coupling (e.g., chemical bonding), communicative coupling, electrical and / or electromagnetic coupling (e.g., capacitive coupling, inductive coupling, direct and / or connected coupling), mechanical coupling, operative coupling, optical coupling, and / or physical coupling.

[0056] It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications can be made to the above- described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

Claims

Attorney Docket: 222204-2960 CLAIMS Therefore, at least the following is claimed:

1. A liquid metal paste, comprising: liquid metal; and copper elements mixed with the liquid metal to form a conductive mixture.

2. The liquid metal paste of claim 1, wherein the liquid metal comprises a gallium- indium liquid metal.

3. The liquid metal paste of claim 1, wherein the liquid metal comprises a eutectic gallium-indium liquid metal having a gallium to indium mass ratio of 3:

1.

4. The liquid metal paste of claim 1, wherein the liquid metal paste comprises up to approximately 30 percent by mass of the copper elements.

5. The liquid metal paste of claim 1, wherein the liquid metal paste comprises approximately 4 percent by mass of the copper elements.

6. The liquid metal paste of claim 1, wherein the liquid metal paste comprises approximately 7 percent by mass of the copper elements. The liquid metal paste of claim 1, wherein the copper elements comprise at least one of a nano-sized copper particle or a micron-sized copper particle.

8. The liquid metal paste of claim 1, wherein at least one of the copper elements is approximately 500 nanometers in size.

9. The liquid metal paste of claim 1, further comprising an elastomer material mixed with the liquid metal to form a conductive and adhesive mixture.Attorney Docket: 222204-2960 10. The liquid metal paste of claim 1, further comprising a silicone material mixed with the liquid metal to form a conductive and adhesive mixture.

11. The liquid metal paste of claim 1, further comprising a polyurethane material mixed with the liquid metal to form a conductive and adhesive mixture.

12. The liquid metal paste of claim 1, wherein the liquid metal comprises a eutectic gallium-indium-tin liquid metal.

13. The liquid metal paste of claim 1, wherein the liquid metal comprises a bismuth- indium-tin liquid metal.

14. The liquid metal paste of claim 1, wherein the liquid metal comprises a bismuth- lead-tin liquid metal.

15. The liquid metal paste of claim 1, wherein the liquid metal comprises a lead-tin- cadmium liquid metal.

16. The liquid metal paste of claim 1, wherein the liquid metal comprises at least one of gallium, indium, tin, bismuth, lead, or cadmium liquid metal.

17. The liquid metal paste of claim 1, further comprising at least one of iron, zinc, nickel, silver, gold, titanium, or platinum elements mixed with the liquid metal.

18. The liquid metal paste of claim 1, wherein in an uncured state, at least one of the liquid metal paste or the conductive mixture comprises a conductive semi-solid mixture.

19. The liquid metal paste of claim 1, wherein in a cured state, at least one of the liquid metal paste or the conductive mixture comprises a conductive semi-solid mixture.

20. The liquid metal paste of claim 1, wherein in a cured state, at least one of the liquid metal paste or the conductive mixture comprises a conductive solid mixture.Attorney Docket: 222204-2960 21. A liquid metal adhesive, comprising: liquid metal; conductive elements mixed with the liquid metal; and an elastomer material mixed with the liquid metal and the conductive elements to form a conductive and adhesive mixture.

22. The liquid metal adhesive of claim 21, wherein the liquid metal comprises a gallium-indium liquid metal.

23. The liquid metal adhesive of claim 21, wherein the liquid metal comprises a eutectic gallium-indium liquid metal having a gallium to indium mass ratio of 3:

1.

24. The liquid metal adhesive of claim 21, wherein the liquid metal adhesive comprises up to approximately 30 percent by mass of the conductive elements.

25. The liquid metal adhesive of claim 21, wherein the liquid metal adhesive comprises approximately 4 percent by mass of the conductive elements.

26. The liquid metal adhesive of claim 21, wherein the liquid metal adhesive comprises approximately 7 percent by mass of the conductive elements.

27. The liquid metal adhesive of claim 21, wherein the conductive elements comprise at least one of a nano-sized conductive particle or a micron-sized conductive particle.

28. The liquid metal adhesive of claim 21, wherein at least one of the conductive elements is approximately 500 nanometers in size.

29. The liquid metal adhesive of claim 21, wherein the elastomer material comprises a silicone material mixed with the liquid metal and the conductive elements to form the conductive and adhesive mixture.Attorney Docket: 222204-2960 30. The liquid metal adhesive of claim 21, wherein the elastomer material comprises a polyurethane material mixed with the liquid metal and the conductive elements to form the conductive and adhesive mixture.

31. The liquid metal adhesive of claim 21, wherein the liquid metal comprises a eutectic gallium-indium-tin liquid metal.

32. The liquid metal adhesive of claim 21, wherein the liquid metal comprises a bismuth-indium-tin liquid metal.

33. The liquid metal adhesive of claim 21, wherein the liquid metal comprises a bismuth-lead-tin liquid metal.

34. The liquid metal adhesive of claim 21, wherein the liquid metal comprises a lead- tin-cadmium liquid metal.

35. The liquid metal adhesive of claim 21, wherein the liquid metal comprises at least one of gallium, indium, tin, bismuth, lead, or cadmium liquid metal.

36. The liquid metal adhesive of claim 21, wherein the conductive elements comprise copper particles, copper flakes, silver particles, or silver flakes.

37. The liquid metal adhesive of claim 21, further comprising at least one of copper, iron, zinc, nickel, silver, gold, titanium, or platinum elements mixed with the liquid metal.

38. The liquid metal adhesive of claim 21, wherein in an uncured state, at least one of the liquid metal adhesive or the conductive and adhesive mixture comprises a conductive and adhesive semi-solid mixture.

39. The liquid metal adhesive of claim 21, wherein in a cured state, at least one of the liquid metal adhesive or the conductive and adhesive mixture comprises a conductive and adhesive semi-solid mixture.Attorney Docket: 222204-2960 40. The liquid metal adhesive of claim 21, wherein in a cured state, at least one of the liquid metal adhesive or the conductive and adhesive mixture comprises a conductive and adhesive solid mixture.

41. A device, comprising: a substrate; a liquid metal adhesive coupled to the substrate; and a conductive component coupled to the liquid metal adhesive, the liquid metal adhesive comprising: liquid metal; conductive elements mixed with the liquid metal; and an elastomer material mixed with the liquid metal and the conductive elements to form a conductive and adhesive mixture.

42. The device of claim 41, wherein the liquid metal comprises at least one of a gallium-indium liquid metal or a eutectic gallium-indium liquid metal having a gallium to indium mass ratio of 3:

1.

43. The device of claim 41, wherein the substrate comprises at least one of a rigid substrate, a flexible substrate, or a stretchable substrate.

44. The device of claim 41, wherein the liquid metal adhesive comprises up to approximately 30 percent by mass of the conductive elements.

45. The device of claim 41, wherein the liquid metal adhesive comprises approximately 4 percent by mass of the conductive elements.

46. The device of claim 41, wherein the liquid metal adhesive comprises approximately 7 percent by mass of the conductive elements.Attorney Docket: 222204-2960 47. The device of claim 41, wherein the conductive elements comprise at least one of a nano-sized conductive particle or a micron-sized conductive particle.

48. The device of claim 41, wherein at least one of the conductive elements is approximately 500 nanometers in size.

49. The device of claim 41, wherein the elastomer material comprises at least one of a silicone material or a polyurethane material mixed with the liquid metal and the conductive elements to form the conductive and adhesive mixture.

50. The device of claim 41, further comprising: a polyurethane film formed on at least one of the liquid metal adhesive, the substrate, or the conductive component.

51. The device of claim 41, wherein the liquid metal comprises a eutectic gallium- indium-tin liquid metal.

52. The device of claim 41, wherein the liquid metal comprises a bismuth-indium-tin liquid metal.

53. The device of claim 41, wherein the liquid metal comprises a bismuth-lead-tin liquid metal.

54. The device of claim 41, wherein the liquid metal comprises a lead-tin-cadmium liquid metal.

55. The device of claim 41, wherein the liquid metal comprises at least one of gallium, indium, tin, bismuth, lead, or cadmium liquid metal.

56. The device of claim 41, wherein the conductive elements comprise copper particles, copper flakes, silver particles, or silver flakes.Attorney Docket: 222204-2960 57. The device of claim 41, further comprising at least one of copper, iron, zinc, nickel, silver, gold, titanium, or platinum elements mixed with the liquid metal.

58. The device of claim 41, wherein in an uncured state, at least one of the liquid metal adhesive or the conductive and adhesive mixture comprises a conductive and adhesive semi-solid mixture.

59. The device of claim 41, wherein in a cured state, at least one of the liquid metal adhesive or the conductive and adhesive mixture comprises a conductive and adhesive semi-solid mixture.

60. The device of claim 41, wherein in a cured state, at least one of the liquid metal adhesive or the conductive and adhesive mixture comprises a conductive and adhesive solid mixture.

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