In situ interfacial engineering enabled mechanically adaptive and highly stretchable liquid metal conductor

Liquid metal (LM) based stretchable conductors have broad application due to their excellent conductivity and deformability. However, the poor interfacial interaction between LM and majority of elastic substrates because of the high surface tension of LM, limits the spread of LM on the substrate and the reconciliatory deformation of LM with underlying substrate. Herein, through the specific affinity between the immediately formed oxide layer on surface of eutectic gallium-indium (EGaIn) and carboxyl groups, an in-situ interfacial engineering for LM conductive coating on hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) (PEO/PAA) elastomers is presented. Particularly, EGaIn patterned on PEO/PAA elastomers can autonomously adapt to the mechanical deformation of substrates to form a stable interface conductive layer, and the slope of deformation ratio between EGaIn layer and PEO/PAA elastomers keeps nearly 1 even at strain of 800%. The design of interfacial interaction also ensures the simultaneous achievement of excellent stretchability and stable conductivity of LM based stretchable electronics, that is, the resistance of the EGaIn conductor will not change significantly and remain below 1 Ω even at a strain of 800%. This work provides guideline for the design of stretchable LM-based conductor.