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 approximately 1.7 N) with an average error of 12.1%.