A sensor skin using wire-free tactile sensing elements based on optical connection

A key to realize an elastic sensor skin that covers the entire body of machines is removing metal wires to tactile sensing elements. Using wireless tactile sensing chips based on RF connection is a hopeful method, which was proposed recently. However, it is difficult to make the RF tactile sensing element smaller than several millimeters because the energy transmission efficiency decreases as the chip size decreases. In this paper we propose a wireless tactile sensing element based on optical connection. The sensing chip with 1 mm cubic shape operates with optical power, and sends optical codes of 6 stress components measured by an optical sensing method. We describe the chip design and the 6 stress sensing principle, and show experimental results of the stress sensing using a prototype of a 4 mm cubic chip. Then we estimated the required optical power for the sensing chip, and checked the operation of the digital circuit on the chip.