EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration

Abstract

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...

Liquid Metal–Based Soft Microfluidics

“…b) Integrated circuit image, including digital IMU and digital temperature sensor, prepared by using self‐aligning method (HCl). Reproduced with permission . Copyright 2018, John Wiley and Sons.…”

Liquid Metal Droplet and Graphene Co‐Fillers for Electrically Conductive Flexible Composites

“…In contrast to the small and reversible resistance change, which is seen for the mild rolled pressed membrane (≈1.0 mm thickness), a very soft roll pressed of less than 10 kPa (Figure d) or not pressed membrane (≈1.3 mm thick in this case) is not able to show a reversibility under high load . Additionally, the initial resistivity is very high (about six orders of magnitude higher, in the case of very soft press).…”

Magnetically‐ and Electrically‐Controllable Functional Liquid Metal Droplets

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including microelectromechanical (MEMS) actuators, [8][9][10][11][12] microscale heat exchangers, [13,14] soft and wearable electronics, [15][16][17][18][19] and reconfigurable structures. [20,21] Several techniques have been developed to control the motion and deformation of liquid metal droplets.

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