Snail-inspired bio-based recyclable liquid-like ionic skins enabling ultra-conformal contact and elasticity recovery for epidermal electronics

Abstract

Booming ionic skins (i-skins) have demonstrated extensive applications in health monitoring, human-machine interfaces, and the Internet of Things. However, existing i-skins often struggle to establish conformal contact with intricate skin topographies and typically do not revert to their original state after deformation due to an imbalance between viscosity and elasticity. Here, inspired by snail mucus, we propose a novel design that encapsulates naturally occurring polyphenols, ionizable compounds, and moisturizing factors in gelatin through well-balanced cross-linking, resulting in a bio-based, liquid-like i-skin (GE/GKG i-skin). The GE/GKG i-skin mimics the softness of natural skin and features excellent elasticity, transparency, and self-adhesiveness. Like snail mucus, this i-skin exhibits an on-demand, thermally responsive, reversible fluid-gel transition that allows it to be applied to the skin as a fluid and solidify in situ into an elastic i-skin, effectively addressing these challenges. Additionally, the reversible phase transition subtly imbues it with outstanding recyclability. This breakthrough i-skin achieves an unprecedented combination of ultra-conformal contact and elastic recovery, dynamically adapting to human skin deformations. It is capable of creating mechanically durable, dynamically adaptable stable interfaces, and supports long-term monitoring of human motion and ECG signals. The proposed strategy provides a general and scalable approach for designing i-skins with customizable features to meet diverse application needs.