Screen-Printed Capacitive\nTactile Sensor for Monitoring\nTool–Tissue Interactions and Grasping Performances of a Surgical\nMagnetic Microgripper

With miniaturization and wireless actuation for a class\nof magnetic\nmicrogrippers for robot-assisted minimally invasive endoscopic intraventricular\nsurgery, surgeons are unable to acquire tactile sensory information\non tissues and organs during tool–tissue manipulation and grasping\ntasks. To minimize the risks of tissue trauma and improve surgical\nperformance, surgeons require haptic feedback technologies to be integrated\nonto microscale surgical tools for tactile information. However, current\nsensors cannot be equipped onto the interior jaw of the microgripper\ndue to low-pressure range and small-scale criteria for RMIS implementation\nfor pediatric neurosurgery. This study proposes a 24 mm<sup>2</sup>, ultrathin, and flexible capacitive tactile sensor for the interior\njaws of a disposable surgical magnetically-controlled microgripper\nto potentially monitor and regulate tool–tissue manipulation\npressures/forces in real time to improve grasping performances and\nquality of surgical procedures. To lower fabrication costs, multiple\nlayers of the capacitive sensor were screen-printed and assembled\nto produce a 100 μm thick sensor. To enhance the range and sensitivity,\nfour different morphologies were developed for the dielectric layer\nand integrated into the sensor design. The dielectric layers were\nfabricated by optimizing and processing thermoplastic polyurethane\n(TPU) into a suitable ink adequate for screen printing large surfaces\nand microstructures. The final optimized capacitive tactile sensor\nwith a grid-like microstructured dielectric design’s electromechanical\nperformance was modeled as a bilinear response with two sensitivity\nmodes for a sensing range of 0.42–54.2 kPa (0.01–1.30\nN applied on 24 mm<sup>2</sup> of gripper jaw). The results also indicated\nperformance comparable to more expensive tactile sensors with a hysteresis\nof 8.8% and a repeatable response to applied cycling loadings with\na maximum response signal decay of 1.85%. This study highlights that\nsimple screen printing method can be used as a low-cost alternative\nto fabricate high-performance tactile sensors to be integrated to\nthe interior jaw of the microgripper designed for disposable endoscopic\nintraventricular surgeries.