Off-the-Jaw Tactile Sensing System for Tissue Stiffness and Thickness Assessment in Minimally Invasive Surgery

The missing tactile sensation in minimally invasive surgery (MIS) presents significant challenges and safety risks in routine surgical procedures. Previous attempts to integrate tactile sensors onto the jaws of surgical tools encountered issues with sterilization, biocompatibility, and wiring complexities. This work introduces a novel 'off-the-jaw' (OTJ) tactile sensing system, which tackles these limitations by integrating force and angle sensors onto the handle of MIS instruments to indirectly measure the grasping force and angle during tissue palpation while preserving the original design and functionality of the grasping jaws. A prototype was developed using a force-sensitive resistor and a rotary potentiometer integrated onto the handle of a laparoscopic grasper. Real-time data processing provides user-friendly visual feedback on tissue thickness and stiffness. Testing was performed using soft elastomeric samples designed to mimic human tissues of varying sizes and stiffness. Initial validation demonstrated a strong correlation between the force applied by the user's thumb on the handle and the force exerted by the grasping jaws on the samples. The sensor-equipped handle successfully differentiated samples based on thickness and stiffness and integrated seamlessly with various surgical end effectors in a plug-and-play manner. Pre-clinical trials with both regular and surgical users revealed significant improvements in sample sorting and lump detection tasks, with up to 30% increase in speed and accuracy. The OTJ technology holds promising potential to improve surgical precision and patient care by restoring tactile feedback in MIS, ultimately contributing to safer and more effective surgical practices.