State-Programmable Conductive and Reactivatable Bio-Adhesive for High-Fidelity Epidermal Biointerfaces

This study developed a printable, state-programmable reactivatable conductive adhesive for high-fidelity epidermal biointerfaces. The material is based on a polyurethane-poly(acrylic acid) graft interpenetrating network loaded with PEDOT:PSS to create ionic-electronic conductive pathways. The RCA can be printed as a viscoelastic conductive gel, dried into a mechanically robust non-tacky film for storage and handling, and then reactivated with a small amount of isopropyl alcohol to recover a soft, conformal, adhesive state. This transition allowed the adhesive to infiltrate skin microtopography and hair-occluded scalp regions while maintaining strong interfacial contact. Increasing PEDOT:PSS content increased conductivity, but also reduced stretchability and adhesion, leading the authors to identify the P4:A6 formulation as the best balance between conductivity, stretchability, and interfacial adhesion. Compared with commercial conductive gel, P4:A6 produced lower skin and scalp impedance with both rigid Ag/AgCl and soft PEDOT:PSS-PU-CNT electrodes, especially in the low-frequency range relevant to electrophysiological signals. EEG recordings from the occipital scalp showed clear alpha rhythms during eyes-closed conditions and alpha suppression during eyes-open conditions, while pulse recordings showed clear periodic waveforms. Human dermal fibroblast extract testing showed no detectable cytotoxicity under the tested conditions. Overall, the study presents a scalable, printable, reactivatable conductive adhesive strategy for stable wearable and clinical bioelectronic interfaces.