A flexible tri-axis contact force sensor for tubular medical device applications

A capacitive, tube-shaped tri-axis contact force sensor is fabricated and characterized in this paper. The sensor is inserted into a tubular medical device just like a small section of tube in order to sense the applied contact force on the tip of this tubular device. It comprises two SU-8 plates, wherein the outer and inner rims of the plates with diameters of 2.3 and 1.1 mm, respectively, are assembled together. Three proof masses were hinged to the outer and inner rims of the first plate by membranes. The different signals received from the three electrodes provide collective information indicating the precision and accurate direction of contact forces exerted on the tip of the tubular medical device. In the test, applied force range from 10 mN to 1.0 N was detected, the performance of the sensor is stable from 25 to 65 °C, and the device was functional under a shock of 2.0 N for 10 s in a shock test. In addition, a two-wire readout approach was also developed to minimize the lead wires.