Liquid Metal Hybrid Composites with High-Sensitivity and Large Dynamic Range Enabled by Micro- and Macrostructure Engineering

Conductive elastic composites composed of conductive fillers and polymer matrices are showing an increasing number of applications in the fields of flexible sensors, wearable devices, and stretchable electronics. Under mechanical deformation, the conductive filler network in the matrix shifts to change the conductive pathway among particles and thus, electrical conductivity of the composite. For most conductive composites, their conductivity changes monotonically with strain. Here, we report a composite that exhibits an unconventional strain response; its electrical conductivity increases sharply under both compressive and tensile loads. The Ecoflex-based composite contains spike-shaped nickel microparticles and liquid metal microdroplets. Because of the elastomeric mechanical properties of Ecoflex, the composite has an extremely high stretchability and pressure sensitivity, which is ideal for tactile sensing and mechanical responsiveness. On the basis of a composite film with a grooved or pyramidal surface structure, we demonstrate a pressure-controlled intelligent heating film and a pressure sensor with extremely high sensitivity and dynamic range.