Intrinsically Conductive, Optical Transparent, and Underwater Self-healing Ionogel with On-Demand Bonding Triggered by Skin Temperature

Abstract

In the field of ionogels, reversible bonding–debonding triggered by mild and accessible stimuli is highly demanded especially for the use of bioelectric electrodes. In addition, the consistent stability of ionogels in underwater conditions are also needed to deal with complex practical scenarios. Herein, an intrinsically conductive, transparent, and underwater self-healing ionogel with on-demand bonding triggered by skin temperature is proposed. The ionogel is designed by incorporating long alkyl side chains into a chemically–physically crosslinked fluorine-rich elastomer with ionic liquid (IL) encapsulated as the conductive media. The long alkyl side chains undergo a semicrystalline-to-amorphous transition between 20 and 32 °C, resulting in large conductivity and adhesion variation of the ionogel. It can be reversibly bonding and debonding with the skin for more than 500 cycles without electrical/mechanical property degradation. The unique morphology with adaptive, conductive IL islands and ion shuttles ensure a high conductivity (1.3 × 10⁻² S m⁻¹) above the skin temperature even under 800% deformations. When utilized as bioelectric electrodes, the ionogel exhibits long-term stability, reusability, and high precision for electromyography and electrocardiogram signal collecting. This study proposes a new design of reversible bonding–debonding ionogel, which can be used in wet environments such as sweaty bodies and underwater conditions.