Electrofluids with tailored rheoelectrical properties: liquid composites with tuneable network structures as stretchable conductors

Abstract

Flexible and stretchable electronics require both sensing elements and stretching-insensitive electrical connections. Conductive polymer composites and liquid metal structures are highly deformable but strongly change their conductivity upon elongation. Macroscopic Kirigami structures combine stretchability with constant conductivity, but their use is limited by geometrical restraints. Here, we introduce concentrated conductive particle suspensions based on Carbon Black as conductive “Electrofluid”. When using incompatible solvents, large agglomerates form that reduce the electrical percolation threshold by one order of magnitude and act as microscopic Kirigami-like structures with very small gauge factors < 0.4. In compatible solvents, well-dispersed fillers exhibit high percolation thresholds, high stiffness, and positive piezoresistivity (gauge factor > 2). Electrofluids enable the rational design of sustainable soft electronics components by simple solvent choice and can be used both as sensor and electrode materials, as we demonstrate.