Fabrication and transient responses of highly flexible and humidity-insensitive ionic polymer–metal composites in different sensory modes

Abstract

Ionic polymer–metal composites, although with attracting properties such as flexibility, easy processing, resilience, and high sensitivity, have some drawbacks including the fragility of electrodes and strong humidity dependence which limit their practical applications. This study aims to fabricate ionic polymer–metal composites with sputtered gold thin film electrodes and to coat them with a waterproof acrylic material to extend their consistent sensory response over time. For this aim, after explaining the sensing mechanism of ionic polymer–metal composites based on streaming potential hypothesis for compression, bending, and shear modes, the fabrication process of the proposed ionic polymer–metal composites is presented. A signal conditioner is designed based on the measurement results of the equivalent resistance and capacitance of the devices. A shock tube setup is then utilized to obtain the impulse response of fabricated ionic polymer–metal composite devices in different modes of deformation. To verify how this waterproof coating maintains the ionic polymer–metal composite’s sensing performance, some experiments are carried out over a period of 6 days after fabrication for both acrylic-coated and uncoated samples. Analyzing the results shows that fabricated ionic polymer–metal composites represent an appropriate linearity, sensitivity, and reliability over time and this coating approach not only suppresses the diluent permeation but also has a negligible effect on the ionic polymer–metal composite electromechanical properties.