Conductivity controllable rubber films: response to humidity based on a bio-based continuous segregated cell network

Abstract

Conductive rubbers are emerging in many applications including wearable devices, human health monitoring, and robotics. However, the design of rubbers with tailorable conductivity remains a great challenge because the conductive filler loading is fixed once the fabrication of a conductive rubber is complete. Herein, a simple strategy is proposed to introduce a continuous biomass segregated network into the rubber matrix and fabricate a flexible film with tailorable electromechanical properties. The conductive rubber film is prepared using carboxyl styrene butadiene rubber (XSBR) and sodium lignosulfonate (SL) biopolymer via latex film-formation. The bio-based segregated network formed by regenerated SL (rSL) serves as an integral skeleton texture that provides the un-crosslinked rubber film with considerable tensile strength up to 10.7 MPa. More importantly, the hygroscopicity of the rSL network endows the film with tailorable conductivity through the regulation of absorbed water content. The resistance change (R/R₀) in the conductive rubber film can be changed from 1 to 3 × 10⁻³, corresponding to water content ranging from 0 to 9 wt%. The rubber film displays a significant response to changes in humidity and can, therefore, be used as a humidity responder to monitor environmental humidity. Furthermore, the rubber film shows a sensitive and stable strain response when electromechanical properties reach a balance, demonstrating the potential of application in wearable devices.