A novel, flexible and ultra-thin pressure sensor for concentric tube manipulators in intra-ventricular neurosurgery robotic tools

Tianhao Chen (1,2), Zia Saadatnia (1,2,3), Hani Naguib (4,5)

1. Institute of Biomaterials and Biomedical Engineering, University of Toronto

2. Department of Mechanical and Industrial Engineering, University of Toronto

3. Department of Materials Science and Engineering, University of Toronto

Minimally invasive endoscopic intraventricular surgery is a robot-assisted technique that has improved patient outcomes with less wound healing time due to small size of incisions. Small and dexterous surgical tool can be designed and miniaturized to a size of 2 mm while maintaining its dexterity and force required to resect brain tumors without open-skull surgery. To provide instrument-tissue interaction information for this tool, force feedback is required to ensure safety and effective operation. In this study, a small and highly sensitive smart material-based sensor was designed and integrated to the tool shaft, known as the concentric tube manipulators. A 200 um- ultrathin layer of micropatterned resistive carbon-filled polyvinylidene fluoride (PVDF) conductive polymer was wrapped spirally around the 2 mm-diameter concentric tube for static and quasi-static force sensing. A layer of interdigitated electrodes was designed to achieve pressure readings with both directional and locational information. Optimizations were performed on the size, pitch and shape of the microstructures as well as the width and spacing of the electrodes to improve sensitivity with reduced hysteresis. The finalized design can sense a pressure down to 0.55 kPa while retaining its flexibility, biocompatibility and sterilizability. The sensor will also enhance more intuitive force feedback for surgeons to use the dexterous neurosurgical tool, which will have a significant impact on brain tumor and epilepsy practice.

Keywords: Minimally invasive surgeries, conductive polymer, interdigitated electrodes, microstructures, force feedback.