Design of a piezoresistive triaxial force sensor probe using the sidewall doping method

In this study, we propose a triaxial force measurement sensor probe with piezoresistors fabricated via sidewall doping using rapid thermal diffusion. The device was developed as a tool for measuring micronewton-level forces as vector quantities. The device consists of a 15 mu m thick cantilever, two sensing beams and four wiring beams. The length and width of the cantilever are 1240 mu m and 140 mu m, respectively, with a beam span of 1200 mu m and a width of 10-15 mu m. The piezoresistors are formed at the root of the cantilever and the sidewalls of the two sensing beams. The sensor spring constants for each axis were measured at k(x) = 1.5 N m(-1), k(y) = 3.5 N m(-1) and k(z) = 0.64 N m(-1). We confirmed that our device was capable of measuring triaxial forces with a minimum detectable force at the submicronewton level.