Triaxial piezoresistive force sensor probe with high sensitivity and stiffness using 3D notch structure

Abstract This paper proposes a microelectromechanical system triaxial piezoresistive force sensor probe with high sensitivity and stiffness. The sensor probe is composed of a cantilever and four supporting beams. Two of the four beams had horizontal notch parts at the root, and sidewall-doped piezoresistors were utilised to detect the in-plane deformation. There was a vertical notch at the root of the remaining two beams and a surface-doping piezoresistor in one beam to detect the out-of-plane deformation. Thus, the proposed sensor probe measures the three directional forces applied to the cantilever tip with high sensitivity and stiffness owing to the corresponding piezoresistive notch structures. We demonstrate a fabrication process that forms the notch structure and the surface and sidewall doping methods. Our fabricated device was confirmed capable of measuring triaxial forces with a force resolution at the sub-micro-Newton level.