Mechanical sintering-induced conductive flexible self-healing eGaInSn@PDA NDs/TPU composite based on structural design to against liquid metal leakage

Room-temperature liquid metals are potential candidates for developing flexible and reconfigurable conductive composites. However, an auxiliary sintering process is required to rupture the oxide and organically modified layers on the liquid metal (LM) nanodroplets (NDs) surface to reactivate their conductive and fluidic properties, thereby forming a continuous conductive pathway inside the composite. However, such a destructive strategy leads to leakage of liquid metal and destruction of composite integrity. Here, the "solvent volatilization strategy" was introduced to cause the organic solvent within thermoplastic polyurethane (TPU) to rapidly volatilize and be actively degassed during the polymerization process, forming densely packed micron-scale cavities. The polydopamine (PDA)-modified eGaInSn NDs were uniformly distributed and anchored to the inner wall of the cavity, providing sufficient filling space for the stress-ruptured eGaInSn@PDA NDs. During the application of mechanical pressure, the composite gradually converted from a dielectric state to a conductive state and it was able to quickly and repeatedly self-healing to restore conductivity after fracturing. In particular, no liquid metal pump-out or leakage was observed on the composite surface even after applying an 8 MPa high stress. In addition, the composite embedded with a high fraction eGaInSn@PDA NDs still exhibited high flexibility and had excellent electromagnetic shielding and X-ray attenuation capabilities.