Additive Manufacturing of Elastic Conductors with Slippery Liquid Metal Particles

Liquid metal particle (LMP) polymer composites are gaining attention in soft robotics, skin electronics, and implantable devices due to their excellent conductivity and stretchability, making them ideal for stretchable conductors. However, composite inks based on liquid monomers or polymer solutions present challenges for 3D printing due to their fluidity. Additionally, in fused deposition modeling (FDM) 3D printing, the high stress during extrusion can damage the LMP's oxide shell, leading to leakage, process contamination, and potential electrical shorts. Here, I present a leakage-free additive manufacturing process for liquid metal polymer composites, enabling the customized 3D printing of elastic conductors. We induced slip on the LMP surface before the oxide shell ruptured, preventing LM leakage even under cutting damage. This high physical stability facilitated the direct printing of 3D circuits within multi-material objects, selectively imparting electrical conductivity and enhancing design flexibility. Furthermore, the strain-insensitive resistance over 500% strain addresses a key limitation in soft robotics by clearly differentiating sensors from electrodes.