Reliable and Reversible Contact of Eutectic Gallium Indium and Copper Electrodes

Abstract Physically reconfigurable electronics provide a unique method to significantly increase the range of capabilities that a single component can possess. Room temperature liquid metal gallium alloys provide this function as a fluid that can be mobilized to drastically modify electrical performance in devices, such as tunable antennas, high isolation switches, and mechanically responsive stretchable electronics. One of the most critical limitations of using gallium alloys for reconfigurable electronics is the irreversible interactions at the interface between the liquid gallium alloy and a traditional solid electrode. In this work, the effect of repeated connection/disconnection cycles on the electrical performance of eutectic gallium indium, a common liquid gallium alloy, and a copper electrode is characterized. The effects of environment, surface treatment, and method of contact between the liquid metal and the solid surface are identified. The failure mechanisms which prevent the reversibility of the electrical interface of these contacts are determined and a mitigation strategy is provided which resulted in 1000 reversible contacts with no degradation in electrical performance.