Design of an ultra thin strain sensor using superelastic nitinol for applications in minimally invasive surgery

This paper introduces a novel ultra thin strain sensor made of superelastic nitinol wire that is well suited for force sensing applications of surgical instruments. The sensing principle used for the described sensor is the same as that for conventional strain gauges; however, the proposed sensor has significant advantages of thinner size (15 μm diameter), higher gauge factor (3.5), large strain measurement range (up to 4.25%), lower cost and easier installation process. To validate its force sensing capability for minimally invasive surgical instruments, the sensor was mounted on a da Vinci surgical tool to measure the lateral forces acting at the distal end. Experimental results showed that the sensor can accurately measure forces with an RMS error of 32 mN and with a resolution of 55 mN.