Development of a single-chip elasticity sensor using MEMS-based piezoresistive cantilevers with different tactile properties

Abstract

In this paper, we propose a micro-electronic-mechanical systems (MEMS)-based tactile sensor that can measure the elasticity of an object without having to measure the contact force and the object’s deformation. In our sensor design, a sensor chip that has three piezoresistive cantilevers is covered by a polydimethylsiloxane (PDMS) pad. The elasticity of an object pressed against the sensor is measured from the ratio of the deformations at different locations of the PDMS pad. One cantilever (C1) is designed to measure the deformation of the center of the PDMS pad, while the other two cantilevers (C2 and C3) are designed to measure the deformations of the outer ends of the PDMS pad. When the sensor is pressed against an object, the ratio of the deformations of the outer ends over that of the center of the PDMS varies depending on the object’s elasticity but not on the pressing force. Therefore, it is possible to measure the object’s elasticity from the ratio of the cantilevers’ outputs. Here, we report on the sensor design, numerical analysis, sensor fabrication, and demonstration of the elasticity measurement using the fabricated sensor. The proposed sensor is expected to be useful in practical applications, including robotic hand manipulation and tissue stiffness discrimination in minimally invasive surgery.