A large range multi-axis capacitive force/torque sensor realized in a single SOI wafer

Abstract

A silicon capacitive force/torque sensor is designed and realized to be used for biomechanical applications and robotics. The sensor is able to measure the forces in three directions and two torques using four parallel capacitor plates and four comb-structures. Novel spring and lever structures are designed to separate the different force components and minimize mechanical crosstalk. The fabrication process is based on deep reactive ion etching on both sides of a single silicon-on-insulator wafer and uses only two masks making it a straight-forward and robust process. The sensor has a force range of 2 N in shear and normal direction and a torque range of more than 6 N mm. It has a high sensitivity of 38 fF N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 550 fF N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in shear and normal direction respectively.