Soft Liquid Metal Infused Conductive Sponges

Liquid metal droplets of gallium (Ga) and Ga-based alloys are traditionally incorporated as deformable additives into soft elastomers to make them conductive. However, such a strategy has not been implemented to develop conductive sponges with real sponge-like characteristics. Herein, polyurethane-based sponges with Ga microdroplets embedded inside the polyurethane walls are developed. The liquid phase (at 45 °C) and solid phase (at room temperature) transition of the Ga fillers shows the temperature-dependent functional variations in the mechanical, thermal, and electrical properties on the prepared composite sponges, which are investigated in detail. Unlike elastomers, the sponge possesses excellent elastic recovery, at ≈90%, and conductivity durability without sacrificing structural integrity. The reversible change of resistivity range is remarkable. When the Ga fillers account for 18% of the total sponge volume, the electrical resistivity varies from infinite values (insulator) under no applied pressure to 39.0 Ω m for the solid phase and 3.8 Ω m for the liquid phase under 386.8 kPa. New opportunities in developing flexible electrically conductive composite sponges with tunable mechanical and electrical properties that can be implemented for a variety of future applications are proposed.