EndoTac: An Endoscopic Camera-Based Tactile Sensor with High Sensitivity for Minimally Invasive Surgery

Minimally invasive surgery (MIS) removes direct tactile feedback from surgical procedures, making it challenging for surgeons to manipulate delicate anatomy, such as vasculature and other soft tissue. Existing tactile tools developed for MIS in prior research are either too bulky or have limited sensing coverage, restricting their utility in practical surgical workflows. To address these challenges, we introduce EndoTac, a novel miniaturized vision-based tactile sensor designed to traverse a standard trocar while offering a large sensing area with high sensitivity. EndoTac integrates an endoscopic camera to achieve a compact and MIS-compatible form factor, and employs a convex mirror to capture the contact information across a wide sensing area, thereby maximizing effective sensing coverage. A soft membrane further enables the sensor to achieve high sensitivity by deforming under gentle interactions with soft and fragile tissue like vascular structures. Experimental results demonstrate that EndoTac achieves a low detection threshold of 20.5 mN, a high pixel-level sensitivity slope in the low-force regime, improved force resolution, and reliable estimation of vessel deformation in vascular palpation tests. Together, these results show that EndoTac provides a significant step toward restoring tactile perception in MIS, offering a practical pathway to safer and more precise surgical manipulation.