A micromachined piezoelectric tactile sensor for use in endoscopic graspers

Present day endoscopic graspers do not have any sensors built in them. Thus the surgeon cannot estimate the amount of pressure being applied to manipulate the tissue safely. The paper reports on the design, fabrication and results of a silicon micromachined piezoelectric tactile sensor which can be integrated on to the tip of the endoscopic grasper. The sensor has a rigid tooth-like surface similar to the present day endoscopic grasper. It consists of upper silicon, a perspex substrate and a patterned polyvinylidene fluoride(PVDF) film, which is sandwiched between the two layer. It is shown that the magnitude and the position of the applied force on the sensor can be found from the magnitude of the output signals from the PVDF sensing elements and the slope of the signal at the position of the application of the force respectively. The sensor exhibits high force sensitivity, large dynamic range and good linearity. The theoretical analysis of the sensor is made and compared with the experimental values. The advantages and limitations of the sensor are also reported. Since the sensor simulates the teeth-like surface of the existing endoscopic grasper, it is possible to integrate the device on to the grasper of the endoscopic surgical instrument.