Characterization of a silicon-based shear-force sensor on human subjects

A silicon sensor is developed and its ability to measure both compressive and shear forces at the skin-object interface is characterized. The sensor is designed based on the piezoresistive effect and fabricated using integrated circuit and microelectromechanical systems technologies. The sensor utilizes a mesa structure that leads to asymmetric diaphragm deformations in response to nonnormal loading. Four independent ion-implanted piezoresistors are used to detect the stresses induced in diaphragm and resolve both the compressive- and shear-force components. The sensor is calibrated on human subjects over a range of applied force (5- to 40-N shear force at increments of 1.25 N; 0- to 30-N compressive force). Force measurement via a tracking experiment is evaluated at four shear (9, 18, 25, and 35 N) and three compressive (7, 15, and 26 N) force levels. The sensor has good repeatability (SD≅1.7 N) with an average error of 12.1%.