Study of piezo-electric elastomer as tactile sensor of a robot

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Aiming an application to the tactile sensor of a robot, we investigated the preparation and physical properties of piezo-electric elastomers. Three types of piezo-electric elastermers were designed namely, space-charge type (SC), parallel dipole type (PD), and rubber-rod-like polymer blend type (RRB). As an SC type elastomer, we used an emulsion of poly (propylene oxide) (PPO) doped with lithiumperchlorate and telechelic poly (dimethyl siloxane) (PDMS) which cross-links by heating. The morphology change under an electric field was first investigated for uncross-linked system. The migration of charged droplets towards the electrodes resulted in a deviation of the distribution of space charge. Based on this observation an electret composed of PPO/PDMS was prepared by cross-linking of PDMS under a strong electric field. The elastomer exhibited piezoelectricity higher than that of poly (vinylidene fluoride). Complicated piezoelectric sygnals were observed depending on the manner of applying stress indicating that the elastomer can distingush objects on which are touching the elastomer. As a PD type piezo-electric elastomer, we used stirene-isoprene-sryrene triblock copolymers (SIS) in which the isoprene block has a dipole aligned in the direction parallel to the chain contour and the stirene block acts as the cross-link. The results of dielectric measurements of SIS indicate that polarization is achieved by jump of the stirene block chains from one domain to the other. To inverstigate the rate of polarization in an RRB type elastomer, we carried out dielectric measurements on poly (hexyl isocyanate) /polyisoprene/toluene ternary system.