A self-compensating stretchable conductor based on a viscous fluid for wide-range flexible sensors

Abstract

Stretchable conductors (SCDs) are one of the essential functional elements for soft electronics, such as next-generation wearable and bio-implantable devices. However, most of the reported SCDs display a variable conductivity upon deformation, resulting in a high error level of electrical signals. Here, we develop a full-filled SCD composing an Ecoflex silicone rubber substrate and a novel conductive filler, i.e. a viscous fluid containing graphitized carbon black (GCB) and sodium chloride (NaCl). These two components show opposite electrical responses during stretching: the conductivity of GCB reduces due to the piezoresistive effect, but the ionic carriers from NaCl enhance the conductivity because of cellulose nanofiber (CNF, the only insulated component in the fluid) reversal, namely the shutter effect. The cooperative effects endow the fluid with excellent conductivity and stability during stretching (i.e. self-compensation), only slight resistance change (≤6.7%) over a large tensile range (100%, GF ≤ 0.07). Our stretchable conductor presents a satisfactory stable electrical performance under various deformations (e.g. twisting, bending, and stretching) simulating real wearing situation. This work provides a unique and efficient avenue for the preparation of stretchable conductors.