Needle Tip Force Sensor for Medical Applications

Abstract

We present a 10 N nominal needle tip force sensor based on silicon-based semiconductor strain gauges that can be used in brachytherapy or biopsies. As deformation body the guiding rod of such a surgical needle with a diameter of 1.2 mm is used. In a thinned area, near the tip of the needle, the strain gauge, as sensing element, is applied with a flexible PCB for electrical connection. Two needles are built and characterized using a testing machine. The sensors provide sensitivities of 6.1 mV/N and 6.4 mV/N for only 1 mA supply current of the bridge, respectively. The linearity and hysteresis errors are in the range of 0.6 % to 4.4 %, which allows measuring interaction forces at the needle tip. Our results prove that the force sensor will provide new measurement means or applications with haptic feedback or for robotic insertion tools.