Electrofluids\nwith Tailored Rheoelectrical Properties:\nLiquid Composites with Tunable Network Structures as Stretchable Conductors

Abstract

Flexible and stretchable\nelectronics require both sensing elements\nand stretching-insensitive electrical connections. Conductive polymer\ncomposites and liquid metals are highly deformable but change their\nconductivity upon elongation and/or contain rare metals. Solid conductive\ncomposites are limited in mechanoelectrical properties and are often\ncombined with macroscopic Kirigami structures, but their use is limited\nby geometrical restraints. Here, we introduce “Electrofluids”,\nconcentrated conductive particle suspensions with transient particle\ncontacts that flow under shear that bridge the gap between classic\nsolid composites and liquid metals. We show how Carbon Black (CB)\nforms large agglomerates when using incompatible solvents that reduce\nthe electrical percolation threshold by 1 order of magnitude compared\nto more compatible solvents, where CB is well-dispersed. We analyze\nthe correlation between stiffness and electrical conductivity to create\na figure of merit of first electrofluids. Sealed elastomeric tubes\ncontaining different types of electrofluids were characterized under\nuniaxial tensile strain, and their electrical resistance was monitored.\nWe found a dependency of the piezoresistivity with the solvent compatibility.\nElectrofluids enable the rational design of sustainable soft electronics\ncomponents by simple solvent choice and can be used both as sensor\nand electrode materials, as we demonstrate.