Design and fabrication of a microtactile sensor

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. We propose a micromachined membrane endoscopic tactile sensor that can measure both static and dynamic applied pressure. In this paper we describe the design, fabrication of a micromachined tactile sensor, which can be integrated, with the tip of the endoscopic grasper. The sensor consists of two 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 in TMAH. 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. The static response is obtained by measuring the change in capacitance between the bottom electrode of the PVDF film and the electrode deposited on surface of the etched cavity under the membrane. The dynamic response of the device is determined by the output potential difference across the PVDF film. The sensor can also be integrated with a commercial endoscopic grasper.