Skin Temperature-Triggered switchable adhesive coatings for wearing comfortable epidermal electronics

Smart adhesives with switchable adhesion strength on demand are crucial for ensuring the stability of the epidermal electronics-skin interface and preventing skin damage caused by device detachment. However, challenges such as harsh triggering conditions, lack of precise control over material comprehensive performance, and difficulty in achieving micron-level controlled integration of materials on device surfaces hinder the application of switchable adhesives in epidermal electronics. Herein, we designed a coatable, thermally-triggered switchable adhesive that has a high adhesion of 68.8 N/m at skin temperature, e.g., 33 °C, and after a slight cooling, e.g., 20 °C, the adhesion decreases to 6.59 N/m, resulting in a high switching ratio of 10.4. The switching time is < 1 min. This unique property is achieved by combining side-chain crystalline polymers and self-adhesive polymers through a strategy of constructing core–shell particles. The results of thermal analyses, rheology, and solid-state nuclear magnetic resonance indicate that a rapid and reversible crystallization-melting transition within the material is the essence of the adhesion switching. By depositing the material on flexible electrodes using spraying technology, we have obtained an ultra-thin (<5 μm), and peelable on-demand epidermal electrode, demonstrating the advantages of emulsion materials in the fabrication of wearing comfortable devices.