Multilayer liquid metal stretchable inductors

Abstract

Liquid metals are ideally suited for creating low resistance traces able to undergo large mechanical strains. In this work, multilayer fluidic channels in soft silicone are used to create two inductor topologies, a solenoid and a double planar coil, based on the liquid metal galinstan. Electromechanical models were developed for the inductance upon stretching for each inductor, finding that the double planar coil has lower strain sensitivity in each direction than the solenoid. A three turn double planar coil and six turn solenoid, with unstretched inductances of approximately 250 nH and 55 nH respectively, were fabricated and tested using custom tensile and compressive strain testing setups and compared with the analytical model. The double planar coil was found to increase in inductance when stretched in either in-plane axes, with a measured rise of approximately 40% for 100% strain. The solenoid decreased in inductance by 24% for 100% strain along the core direction, and increased by 50% for the same strain along the core width.