Development of Capacitive Tactile Sensors for Surgical Systems

Book excerpt: Minimally invasive surgery (MIS) has gained popularity over traditional open surgery due to its advantages of decreased incision size and pain to the patient, lower risk of infection, and shorter recovery time. Recent developments in robotic surgical systems have shown promise to further advance MIS by offering the surgeons with increased manipulability and dexterity along with 3D vision. However, one major disadvantage associated with robotic surgery is the absence of tactile feedback, which is critical in tool-tissue interaction. This paper provides an overview and information useful for approaching a novel tactile feedback sensor system. We aim to construct highly sensitive micro-scale tri-axial capacitive-based differential force sensors that will be integrated at the tips of surgical tools used in robotic surgery. To date, three capacitive sensor models have been proposed. Comb drive model, joystick model and single-sided capacitive sensor model. The first two models were initially created by COMSOL, with optimized geometry parameters. We demonstrate that all three models can satisfy the sensitivity and resolution requirement after being connected with a readout circuit. The fabrication process is proposed and short-loop experiments have been conducted. The integration of read-out circuits with the capacitive sensor is designed on a flexible printed circuit board, which will be first connected to the computer with LabVIEW based controller to convert the analog signal to digital capacitor signal, and the force information as well as the real-time sensitivity, resolution values can be obtained. After the functionality of the sensor is proven to be valid, the proposed tactile sensor system needs to integrate into current Haptic Feedback System. Both the microcontroller and the software need to be modified to function with the proposed sensor and the actuators.