Bioinspired 3-D Tactile Sensor for Minimally Invasive Surgery

This paper reports the development of a bioinspired 3-D tactile sensor for minimally invasive surgery. Inspired by the principle of hair cells, the sensor is composed of a central silicon post and a piezoresistor-embedded polyimide diaphragm to which the silicon post is attached. The high-aspect-ratio silicon post helps to increase the sensitivity to shear force significantly. Another unique advantage is that the silicon post is surrounded by a cylindrical cavity that provides a safety stop for the excessively large force/displacement. A fabrication process using deep reactive-ion etching, as well as a simple but effective packaging scheme, was demonstrated. The packaged tactile sensor was characterized by monitoring the resistance change of the piezoresistors when the central post was pushed in different directions. The sensor exhibited a shear force sensitivity of 10.8 N^-1 and a normal force sensitivity of 3.5 N^-1. The measured displacement sensitivities in shear and normal directions are 1.2 × 10^-3 and 6.0 × 10^-3, respectively. The responses of single and multiple sensors to the rubber scratching test were studied to demonstrate the capability of the sensor to detect the direction and other information of the scratching.