Artificial hair cell sensors using liquid metal alloy as piezoresistors

In this paper, we present the design, fabrication process, and testing results of an artificial hair cell sensor made by liquid metal encapsulated in a polydimethylsiloxane (PDMS) substrate. Previously, a flexible force sensor was reported from our group, which can detect both normal and shear forces by using liquid metal alloy (Ga-In-Sn) as piezoresistive gauge material encapsulated in a PDMS substrate. Based on this method, we propose an artificial hair cell sensor which can detect two-axis tactile force with a standing artificial hair shaft. Since the liquid-metal piezoresistors deform with the elastomeric substrate, normal and shear force can be detected with resistance changes of the piezoresistors. Each force sensor comprises a pair of symmetric piezoresistors, which is screen-printed on a suspended PDMS membrane with opposite direction to be sensitive to shear forces. The testing results demonstrate the sensitivity of the force sensor in two-axis directions.