Wireless tactile sensing element using stress-sensitive resonator

Robots that work with humans require a soft sensor skin to cover the entire body. In this paper, we propose a new method to realize such a skin. By implanting wireless sensing elements in an elastic body, we obtain an elastic and tough sensor skin which is able to be shaped freely. The element is a passive resonator chip whose resonant frequency reflects the stress around the chip. The resonant frequency is read out by a ground coil located at the bottom of the skin. The chip is simply composed of three functional parts: a coil for receiving and transmitting electrical power with wireless coupling, capacitance sensitive to stress, and ceramic resonator to provide high-Q resonance. The high quality factor brought by the ceramic resonator enables one to distinguish a large number of chips, and to sense the stress with high accuracy. The structure, the method of wireless signal detection, and basic experiments of tactile sensing are presented.