Effects of electrode degradation and solvent evaporation on the performance ofionic-polymer–metal composite sensors

Abstract

An ionic-polymer–metal composite (IPMC) consists of an ionic polymer membrane andmetallic electrodes plated on both surfaces. When it bends, a voltage is generated betweenthe two electrodes across the membrane. Since it works not only in aqueous solutionsimilar to in vivo but also in air, it can be used for embedded biomedical as wellas surface-mounted sensors. The present study investigates the effect of solventevaporation and mechanisms of electrode degradation of an IPMC when it is operatedas a sensor. The output voltages and electrode resistances were measured withseveral cyclic bending motions applied on the sensor in both aqueous solution andair. There was a good correlation between the sensor voltage and the bendingangle when the sensor was tested in aqueous solution. The sensor worked fora long time without attenuation in the output voltage in an aqueous solution.The output voltage, however, decreased rapidly when the sensor was operatedin air. The results of resistance measurement showed that the electrode on thecompressive side deformed more and generated more cracks than on the tensile side.Optical microscopic images taken on the electrode surfaces validated the results.The results provided very useful information needed to understand electrodedegradation and solvent evaporation and to improve the performance of IPMC sensors.