Stretchable elastomer based on viscous sensing fluid with a positive piezoconductive effect

Conductive elastomers based on a fully filled structure have been widely used in soft electronics, such as wearable strain sensor for human motions detection. These elastomers are typically conductors because of the conductive fillers within elastic substrate, which can directly reflect the deformation via a contact-separation effect between the fillers. Nevertheless, most reported elastomers so far display a negative piezoconductivity, i.e., the conductivity decreases under a tensile strain, which is undesirable since catching a weak conductivity under large deformation is inconvenient. Here, we report a sensing fluid-filled elastomer comprising cellulose nanofibers (CNF–C) and sodium chloride crystals (NaCl), which exhibits an unconventional positive piezoconductive effect (gauge factor is −0.504). Our elastomer uniquely possesses the worst conductivity (σ: 0.28 S/m) in a relaxed state, and increases rapidly when stretches due to the reversion of the CNF–C flakes, namely ‘shutter effect’. Such a novel strain response mechanism has been achieved in a fully filled conductive elastomer, making it prospective in advanced applications such as strain sensors, stretchable conductors, and smart robotics. [Display omitted] •The fluid only comprises CNF–C and NaCl, which are low cost and environmental.•Our recyclable fluid brings new route to solve the electronics garbage pollution.•The device exhibits a novel positive piezoconductivity due to the shutter effect.