Microfabrication of Flexible Self-Repairing Ground Reaction Sensor With Liquid Metal Electrodes

In this paper we present a new technique that produces reliable flexible sensors using self-repairing interconnects. Instead of using conventional serpentine metal film interconnects, the flex sensor uses liquid GaInSn-filled microfluidic channels formed on top of thin Au wires. The free-flowing, low-resistivity GaInSn thus shunts the Au wire resistance forming an electrical bridge whenever a break in the Au wire appears. We implemented a flexible, ground reaction sensor cluster using the self-repairing liquid-metal scheme. The sensor array maps the ground contact forces in pedestrian navigation systems as a navigational aid. The fabricated sensor cluster can measure contact pressure and shear with sensitivities of 0.74 /MPa and 0.22/MPa, respectively. The device was subjected to 600,000 flexing cycles (∼40% strain) without any observable metal connectivity failure or noticeable resistivity degradation.