Abstract

The present day endoscopic graspers are designed to be tooth-like in order to grasp slippery tissue during Minimally Invasive Surgery (MIS). However they do not have any sensing device to provide the surgeons any tactile feedback. This thesis describes the design, fabrication and testing of a micro-machined tooth-like tactile sensor, which can be integrated with the tip of an endoscopic grasper. The sensor consists of three parts; the first part is a 25-micron polyvinylidene fluoride (PVDF) film. The second part is made of a silicon substrate with cavities etched using anisotropic etching of silicon. The bottoms of the cavities are covered with a layer of aluminum. The two parts then are bond to each other in such a way that the lower aluminum layer of PVDF is facing the bottom of the cavities forming a parallel plate capacitor with the aluminum layer in the cavity. The third layer is a 0.5mm thick toothlike plexiglass glued on the top of the PVDF. The static response of the sensor is obtained by applying a static force on the tooth and measuring the change in capacitance between the bottom electrode of the PVDF film and the electrode deposited on surface of the etched cavity. The dynamic response of the device is determined by applying a sinusoidal force on the tooth of the sensor and measuring the output voltage from the PVDF film. The experimental results are compared with both analytical and finite element results. The sensor exhibits high sensitivity and linearity. The sensor can also be integrated with a commercial endoscopic grasper without changing its original design.