Bioinspired Ionic Biogels for Conformal On-Skin Wearable Bioelectronics.

Conductive gels are promising materials for on-skin wearable bioelectronics owing to their softness, ionic conductivity, and tissue-like interfacial characteristics. However, conventional preformed conductive gels often cannot fully accommodate complex and dynamically deforming skin surfaces, thereby limiting their interfacial adhesion and signal-transmission performance. Inspired by the reversible mechanical switching behavior of sea cucumbers, we developed a thermoresponsive ionic biogel (IBG) composed of gelatin, water, and 1-ethyl-3-methylimidazolium ethyl sulfate. In this system, gelatin forms a physical network with reversible sol-gel transition behavior, while the ionic liquid modulates the network through hydrogen bonding and electrostatic interactions and provides mobile ions for charge transport. This design integrates mechanical compliance, skin adhesion, water retention, and electrical functionality. The IBG can be directly coated onto skin in a flowable state and subsequently undergo mild in situ gelation, forming a soft, adaptive, and ion-conductive bioelectronic interface. The optimized IBG43 exhibits a low modulus, high stretchability, strong adhesion, and good environmental stability, together with stable strain sensing, reliable electrophysiological signal acquisition, and potential for self-powered sensing. This work presents a simple and effective strategy for constructing in situ formable skin-interfaced bioelectronic materials.