Influence of environmental conditions and voltage application on the electromechanical performance of Nafion-Pt IPMC actuators

Abstract

Abstract Ionic polymer–metal composites (IPMCs) are a class of ionic-type electroactive polymers which can be configured as capacitor actuators with very low voltage requirements (⩽5 V AC or DC). Their compact, portable, and lightweight properties, coupled with a biomimetic bending actuation response, makes them ideal for human–machine integrated technologies such as medical implants, active skins, and artificial muscles. Unfortunately, IPMC actuator’s hydration-related sensitivity inhibits practical application in industry and makes experimental research difficult. Therefore, this research sought to quantify the hydration-related parameters of IPMC actuators by applying a wide range of experimental tests to characterize the material’s hydration-dependent features. This included saturation, dielectric, and bending actuation measurements. The IPMC’s degree of saturation properties were classified to establish sample rehydration, preparation, and preservation techniques. IPMC electrical-solvent properties were measured to estimate IPMC actuation performance based on capacitance and dissipation measurements. Maximized actuation was identified for samples tested in 95% RH (i.e. percentage relative humidity). This condition produced an optimized displacement range and retained quality. Through statistical analysis, the work showed large electroactive performance variability (up to 50% deviation), which is a primary obstacle inhibiting this technology from practical application. Finally, an array of electrical field bias applications (i.e. cycled, constant, and post voltage removal monitoring) at intensities ranging from 0.75 to 1.2 V (direct current voltage) were used to quantify actuation rate, maximum displacement, as well as voltage application and removal back-relaxation behavior.