Phase transition and mechanochemistry enabled lightweight liquid metal skeleton for multifunctional conductive composites

Stretchable conductive composites show promising applications ranging from wearable electronics to soft robotics. Gallium-based liquid metals (LMs) characterized by both high metallic conductivity and fluidity are ideal deformable fillers for stretchable conductive composites. However, high loading of LM and post-sintering are required to create conductive pathways, leading to high metal consumption, high density of composites, and increased fabrication complexity. Herein, we report a phase transition and mechanochemistry-enabled lightweight three-dimensional LM skeleton with a low density of 0.2 g/cm 3 using a salt sacrificial template strategy. The initially conductive skeleton allows the capillary filling of various polymer precursors for sintering-free and on-demand formation of various functional composites. The resulting LM-Ecoflex composite exhibits low metal loading (3.7 vol%), high conductivity (1.3 × 10 3 S/m) and stretchability (774% strain), and good durability (Δ R  = 1.2% over 10,000 cycles at 100% strain). Moreover, we show the monolithic fabrication of soft robotic actuators, which can be achieved by integrating the LM skeleton with thermally responsive polymers. We also demonstrate potential applications of LM-Ecoflex composites in enhanced electromagnetic shielding and heat transfer. This work provides a versatile way to on-demand create lightweight and multifunctional LM-based soft devices. Graphical A phase transition and mechanochemistry-enabled lightweight three-dimensional liquid metal (LM) skeleton is created using a salt sacrificial template strategy. The initially conductive skeleton allows the capillary filling of various polymer precursors for the sintering-free and on-demand formation of various functional composites. Such lightweight and conductive LM composites have advantages in robotic actuators, electromagnetic shielding, and thermal management.