Abstract
Liquid metal (LM) offers exceptional potential for stretchable and flexible applications due to its outstanding stretchability, flexibility, and electrical conductivity. The inherent characteristics of LM-such as high surface tension, low viscosity, poor wettability, and sintering challenges-pose significant obstacles for use in commercial printing. To overcome these, a self-sintering liquid metal composite particle (LMCP) ink with tunable surface tension, viscosity, and wettability is developed. LMCP inks are tailored for commercial printing processes requiring low surface tension and high viscosity, enabling printing on diverse substrates. The ink achieves coffee-ring-free, crack-free, bilayer-free, and post-processing-free deposition through simple evaporation under ambient conditions, while preserving electrical conductivity. Key innovations include: i) utilizing polyvinylpyrrolidone (PVP)-capped liquid metal particles (LMPs) to reduce surface tension and enhance wettability; ii) incorporating Laponite as a viscosity enhancer and leveraging LMP sedimentation to control viscosity; iii) forming LMCPs encapsulated by PVP and Laponite through co-self-assembly on LMP surfaces to promote self-sintering; and iv) achieving uniform deposition via solutal-Marangoni-driven mixing and particle settling. The resulting LMCP electrodes exhibit over 1200% stretchability, patternability into complex configurations, and stability for nearly one year in air. Additionally, their application as stretchable metamaterial absorbers is highlighted, showcasing their potential in advanced printable electronics.