NiCr MEMS Tactile Sensors Embedded in Polyimide Toward Smart Skin

Piezoresistive NiCr tactile sensors have been developed on surface micromachined aluminum oxide membranes, embedded between two polyimide layers, i.e., one serving as a substrate, another as a superstrate. A novel method to bond a flexible superstrate polyimide layer onto a microelectromechanical system tactile sensor array is presented. The piezoresistors were connected in a half-Wheatstone bridge configuration to minimize the effects of thermal drift. Three different types of sensor designs were fabricated and characterized to obtain the nichrome thin-film gauge factor. The experimental results were compared with those simulated for the same conditions of membrane deflection. The gauge factors range between 2.2 and 7.9 for sensors with a superstrate and between 1.5 and 3.2 without a superstrate.