Paintable biopolymer–liquid metal-based ionic-skin hydrogel for sustainable wearable bioelectronics:

Abstract: Wearable bioelectronic patches are transforming healthcare by enabling continuous monitoring of physiological signals. Nonetheless, existing systems face challenges, including inadequate skin adhesion, gel dehydration, mechanical fragility, and environmental concerns associated with single-use devices. To address these issues, we present a paintable, disposable, and biodegradable ionic-skin hydrogel electrode engineered for clinical-grade electrophysiology and multimodal sensing. This study was designed to integrate stabilized gallium-based liquid-metal networks into a gelatin-carrageenan biopolymer matrix. Carboxylic acid-functionalized F127 serves as an interfacial stabilizer. This formulation yields a soft, breathable surface that retains moisture and conforms seamlessly to the skin. Functional groups present in the matrix interact with the liquid-metal oxide shell, thereby preventing leakage, preserving metallic pathways, and facilitating self-healing under mechanical strain. Consequently, a hydrogel electrode is developed that integrates triboelectric energy generation with piezoresistive pressure sensing while ensuring long-term hydration and biocompatibility. Comprehensive evaluations will examine film formation, flow properties, impedance stability, hydration retention, motion durability, and biodegradation. Functional validation involves ECG, EMG, EEG, and pressure-sensing tests, with metrics like impedance drift, SNR, artifact suppression, alpha-band stability, R-wave accuracy, and pressure sensitivity. The F127 scaffold also offers a modular platform for ion recognition, allowing scalable electrochemical sensing without compromising electrophysiological performance. This study introduces a paintable, environmentally friendly hydrogel patch that can be removed with warm water, thereby ensuring user comfort and reducing environmental impact. By integrating ionic-skin mechanics, liquid-metal conductivity, and molecular stability, the platform facilitates simultaneous monitoring of biopotentials, pressure, and sweat chemistry.