A Highly Integrated 3D MEMS Force Sensing Module With Variable Sensitivity for Robotic-Assisted Minimally Invasive Surgery

In robotic-assisted minimally invasive surgery (RMIS), non-sentient surgical instruments make it impossible for surgeons to perceive operational force during the procedure. To facilitate surgeons with force telepresence during surgery, a highly integrated MEMS-based piezoresistive 3D force sensing module, which is composed of a MEMS-based piezoresistive sensor chip, an encapsulation cap with miniature pyramids, and a top elastic layer, is demonstrated. This innovative combined construction allows for rapid replacement of elastic layers with different thicknesses and different Young's modulus, so as to realize an adjustable sensitivity and measurement range for different surgeries. By replacing the elastic layer, the same amount of change in resistance can be achieved for external force of 3 and 10 N in the Z-axis; the sensitivity in X- and Y-axes can be increased by a maximum of eight and seven times, respectively. Meanwhile, miniature size enables it to be integrated into various surgical instruments’ tip. Experimental demonstrations involving palpation simulated nodule detection of kidney, ex vivo puncture, and threading forces estimation of tissue-mimicking are conducted to validate the effectiveness of adjusting sensitivity and range. This sensing module is potentially a promising solution for low-cost and versatility to surgical instruments, which can facilitate unification of force-sensing/intelligent surgical instruments.