Development and characterization of touch sensing devices for robotic applications

This paper presents the development of touch sensing chips for robotic applications and the experimental results from touch sensing elements on the chip. The high resolution tactile sensing chips have overall dimension of 1.5 cm × 1.5 cm and consist of 25 touch sensing elements. The touch sensing elements on the chip are the POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) devices, obtained by depositing piezoelectric polymer directly on to the gate area of MOS transistor. Each sensing element has an effective sensing area of 0.5 mm × 0.5 mm. The tactile sensing chips are suitable for fingertips of a robot where large numbers of sensors are needed in a small space (typically 1 cm × 1.5 cm). The tactile sensing elements on the chip have been experimentally evaluated in time and frequency domain. Typically, protective rubber films of materials like PDMS (Polydimethylsiloxane) are used to improve robustness of the sensors, albeit, at the cost of reduced sensitivity. Such effects on the response of POSFET touch sensing elements are studied with PDMS films having different thicknesses.