Bio-inspired design of tactile sensors based on ionic polymer metal composites

SUMMARY Ionic polymer metal composites (IPMC) have been widely investigated as newly-emerging materials for transducer applications due to their good performance, such as low weight, good flexibility and large strain. A bio-inspired design was described and applied to build 3-D papillae dome structure for vectorial tactile sensors. INTRODUCTION The electrical-chemical-mechanical effect in ionic polymer metal composites (IPMCs) was first reported by Oguro et al in 1992 [1]. A typical IPMC sample contains an ionic polymeric membrane saturated with solvent (usually water) and counter ions, which is sandwiched by two compliant metal electrodes. Ionic polymer metal composite have already attracted great attention as a recently developed new material for actuator and sensor applications due to its potential as a bio-mimetic candidate. It is physically light and flexible. Moreover, it could be easily actuated under a really low voltage [2, 3]. Conversely, we demonstrated that it was able to sense small deformation or force as sensor [4]. IPMC is a promising candidate for bio-related applications mainly due to its biocompatibility, flexible structures and operation in wet condition [5]. Due to the similarities in the mechanism of electroactive polymer and some biological actuation and sensing systems, we can learn about their energy-conservative sensing and actuation mechanisms as well as the relationship between microstructure and macro-behavior for these intelligent materials [6, 7]. Biological systems are an ideal intelligent structural system with integrated sensing and actuating capability. In Fig.1, the natural mechanosensor of papillae in cucurbitaceae possesses well-developed sensor microstructure and its distributed pattern on the surface is a very good scheme of arrayed mechanosensor system for identification of vectorial forces. Most of the tactile sensors that have been developed so far are based on piezoelectric sensing elements covered by elastomeric top coating or by piezo-resistive mechanism. To extend the sensing capability of tactile sensors in x-y-z three directions, novel design of three dimensional structures based on flexible materials should be achieved.