Hydroxyl-Rich PVA Coating Enables Robust Adhesion of Liquid Metals for Circuit Patterning on Rough Substrates

The practical application of gallium-based liquid metal (GaLM) in flexible electronics is limited by its inherent high surface tension and rapid formation of oxide layers, which hinder its effective adhesion to rough substrates. To address this challenge, this study proposes a strategy: constructing a hydroxyl-rich poly(vinyl alcohol) (PVA) coating that simultaneously planarizes rough substrate surfaces and introduces abundant hydroxyl groups (-OH), enabling strong interfacial adhesion with GaLM oxide layers for patterned circuits on textured substrates. Experimental results reveal that the synergistic effects of surface morphology regulation and hydroxyl-mediated interfacial bonding play a critical role in enhancing GaLM's adhesion across multiple dimensions. Density functional theory (DFT) simulations further elucidate the synergistic effects of hydrogen bonding and covalent bonding at the interface between hydroxyl groups and the GaLM oxide shell. Additionally, flexible electrothermal patches and resistive strain sensors are fabricated by leveraging the selective adhesion of GaLM between hydroxyl-enriched smooth surfaces and rough substrates. This work broadens the selection of substrates for liquid metal-based flexible electronics by enabling the use of rough substrates for circuit fabrication, holding significant implications for wearable devices.