Activation-Free Liquid-Metal Composite Elastomers via Ultrasonic-Enabled Interface Welding for Strain-Insensitive Electronics

Liquid metal (LM)-based stretchable electronics are often limited by their native insulating oxide shell, typically necessitating destructive post-activation or resulting in blends with limited extreme-strain capabilities. Herein, we report an activation-free LM composite elastomer (ALCE) featuring a robust metallurgical interface between LM nanoparticles and silver nanowires (Ag NWs). Unlike conventional physical mixing, we harness acoustic cavitation to facilitate in situ alloying. As the solvent subsequently evaporates, the welded components preferentially sediment to yield a macroscopic gradient architecture. This establishes a continuous conductive bottom network protected by a polymer-rich upper layer, delivering a conductivity of 2.4 × 10⁶ S/m. Benefiting from these robust welded junctions, the ALCE exhibits a distinctive initial decrease in resistance up to 400% strain, compensating for deformation-induced resistance increases to achieve exceptional strain insensitivity (R/R₀ = 1.8 at 1200% strain). Finally, we demonstrate its practical performance with robust stretchable sensors and a skin-conformable human-animal interactive system, establishing a scalable strategy toward high-performance bioelectronics.