Soft Anisotropic Conductors as Electric Vias for Ga-Based Liquid Metal Circuits

Lu, Tao; Wissman, James; Ruthika,; Majidi, Carmel

doi:10.1021/acsami.5b07464

Cited by 71 publications

(63 citation statements)

References 40 publications

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“…A thin layer of Galinstan was applied on top and bottom of the samples to minimize contact resistance at the sample–reference bar interface. The copper reference bars are not affected by gallium within the short timeframe of the measurements …”

Section: Methodsmentioning

confidence: 97%

“…Percolation can be enforced at φ ≪ φ p by imposing a magnetic field on an uncured polymer composite with magnetically permeable fill particles. This simple and cost‐effective process creates composites with highly anisotropic electrical and thermal conductivities that are significantly enhanced along the direction in which the particles are aligned . For example, magnetically aligning spherical nickel particles in a polymer matrix provides a twofold improvement for k c in the direction of particle alignment .…”

Section: Introductionmentioning

confidence: 99%

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Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Ralphs

Kong

Wang

et al. 2019

Adv Materials Inter

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Despite major advancements in the performance of thermal interface materials (TIMs), contact resistance between components persists as a major thermal bottleneck in electronics packaging. In this work, the thermal performance of composite TIMs is enhanced through a synergistic coupling of magnetic alignment and engineered particle coatings that reduce the thermal resistance between particles. By itself, magnetically induced percolation of nickel particles within a cross‐linked silicone matrix doubles the thermal conductivity of the composite. This process significantly increases contact between particles, making the interfacial particle–particle resistance a major contributor to the composites thermal performance. The resistance at these interfaces can be reduced by introducing soft metal (silver) or liquid metal coatings onto the nickel particles. Compressing powder beds of these hybrid particles reveals that, dependent on coating thickness, the contact engineering approach provides multifold increases in thermal conductivity at mild pressures. When dispersed in a polymer matrix and magnetically aligned, the coated particles provide a threefold increase in composite thermal conductivity, as compared to unaligned samples (up to nearly 6 W m−1 K−1 with volumetric fill fraction of 0.5). For equivalent coating thicknesses, silver coatings achieve better performance than liquid metal coatings.

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Section: Methodsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Ralphs

Kong

Wang

et al. 2019

Adv Materials Inter

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“…Figure proposes some emerging approaches for making electrical contacts. The first example involves aligning magnetic particles (Ni) particles in an encasing elastomer (Figure a–e) . These aligned particles can create anisotropic conductors that span from the liquid metal to the exterior of the elastomer.…”

Section: Challenges and Opportunitiesmentioning

confidence: 99%

“…a–e) One solution is to use stretchable, anisotropic conductors composed of conductive magnetic particles aligned in elastomer. Reproduced with permission . Copyright 2015, American Chemical Society.…”

Section: Challenges and Opportunitiesmentioning

confidence: 99%

Stretchable and Soft Electronics using Liquid Metals

2017

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can be patterned into non-spherical shapes using both conventional and unconventional methods to form highly conductive, durable, and stretchable wires, interconnects, and antennas. The deformation limits of conductors formed with liquid metal are only limited -in principle -by the mechanical properties of the encasing material. The geometrical changes to the metal during deformation can be harnessed to form softer-than-skin sensors of strain and touch. Liquid metals can also be utilized as active components in memory devices, diodes, electrodes, and capacitors built entirely from soft materials. In addition, liquid metals can form circuits that are self-healing and shape-reconfigurable.There are many exciting and promising applications that harness the unique properties of liquid metals. Recent advances, opportunities, and challenges with liquid metals based on gallium within the context of stretchable and soft electronics are discussed here.

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“…There has also been increasing focus on the integration of IC chips and other microelectronics to form multifunctional stretchable circuit assemblies. Indirect integration with a rigid printed circuit board (PCB) adapter or z ‐axis conductive film and direct integration of an IC chip with “gull wing” leads, a bare CMOS die, and a custom‐fabricated thin film transistor have all been demonstrated and the charge transport characteristics of self‐assembled monolayer/EGaIn tunneling junctions have been studied . However, direct wetting and interfacial characteristics between LM circuit terminals and the pins of IC microchips have not previously been investigated.…”

Section: Introductionmentioning

confidence: 99%

EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

Özütemiz

Wissman

Özdoğanlar

et al. 2018

Adv Materials Inter

Self Cite

175

167

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provide increased robustness and better mechanical impedance matching with the host material or structure. For instance, they can be integrated into clothing or mounted on the skin without constraining natural body motion or causing discomfort. A promising approach for realizing stretchable electronics is to create microfluidic traces of liquid-metal (LM) embedded in a soft elastomer. [1][2][3] Ga-based LM circuits offer attractive advantages over alternative approaches. Stretchable electronics based on soft-elastomers embedded with percolating networks of rigid metallic particles, [4,5] carbon allotropes, [6,7] or conductive polymers [8,9] typically suffer from low conductivity (three orders of magnitude lower than metals) or poor electromechanical properties. Micro/nanoscale geometries of thin conductive elements (e.g., serpentine and "wavy" electronics) represent a promising alternative that achieves stretchable functionality through flexure or twisting on a prestrained elastomer substrates. [10][11][12][13][14] However, obtaining stretchability with deterministic architectures requires conductive traces to be patterned into specific geometries (e.g., prebuckled waves, planar serpentines) that are only deformable in prescribed directions. By contrast, Ga-based LM alloys, such as eutectic Ga-In (EGaIn; 75% Ga and 25% In, by weight) and Ga-In-Sn (Galinstan; 68% Ga, 22% In, 10% Sn), can be incorporated into elastomers and preserve their elastic properties at all length scales and in all loading conditions without requiring specialized geometries. [15] These alloys provide high electrical conductivity (3.4 × 10 6 S m −1 ), low melting point (−19 °C for Galinstan, 15 °C for EGaIn), low viscosity (2 mPa s), low toxicity, [16] and negligible vapor pressure. [3,15] Since they are liquid at room temperature and have metallic conductivity, EGaIn and Galinstan can function as intrinsically stretchable and deformable conductors that are not subject to the limitations of conductive polymers or deterministic architectures. As such, LM-based electronics can provide a unique combination of metallic conductivity and elastomeric deformability. Although this promise of LM-based electronics has been well recognized in recent literature, [17] advances in scalable fabrication approaches and effective electrical interfaces between liquid metal traces and microelectronics are still needed to create functional and practical soft and stretchable electronics.Eutectic gallium-indium (EGaIn) has attracted significant attention in recent years for its use in soft and stretchable electronics. However, advances in scalable fabrication approaches and effective electromechanical interfaces between liquid metal (LM) traces and microelectronics are still needed to create functional soft and stretchable electronics. In this study, EGaIn-metal interfacing for the effective integration of surface-mount microelectronics with LM interconnects is investigated. The electrical interconnects are produced by creating copper patterns on a soft-elastomer su...

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Soft Anisotropic Conductors as Electric Vias for Ga-Based Liquid Metal Circuits

Cited by 71 publications

References 40 publications

Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Thermal Conductivity Enhancement of Soft Polymer Composites through Magnetically Induced Percolation and Particle–Particle Contact Engineering

Stretchable and Soft Electronics using Liquid Metals

EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

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