Highly Conductive Ag Flakes-Based Bio-Adhesive for Multi-Functional Epidermal Electronics

Robust skin-electronic interfaces are essential for signal fidelity of wearable bioelectronics, particularly under dynamic physiological conditions. In situ fabrication of biocompatible electronics offers a promising strategy to achieve conformal skin-electronic integration through intimate interfacial contact. However, existing in situ-printable conductive inks face inherent trade-offs between high conductivity and strong adhesion, as well as between environmental resilience and on-demand removability, significantly limiting their practical utility. Here, we report a viscoelastic supramolecular polymer-based conductive adhesive ink (AgBioA) that simultaneously achieves high electrical conductivity (>15 000 S cm^-1), strong skin adhesion (∼3 N cm^-1), excellent environmental stability, ethanol-triggered on-demand dissolution, and superior biocompatibility. Our approach leverages a dynamically crosslinked supramolecular network, synthesized by copolymerizing α-lipoic acid (LA) with 1,3-diisopropenylbenzene (DIB) and reinforced with citric acid (CA) via hydrogen bonding. This unique design enables two key innovations: first, it ensures robust interfacial adhesion to diverse surfaces, from biological tissues to rigid electronic components; second, it facilitates the uniform dispersion of silver flakes into mechanically stable, percolated networks that guarantee highly reliable conductivity. Exploiting these advantages, we demonstrate fully integrated epidermal devices, including in situ fabricated bioelectrodes for reliable electrocardiography (ECG) and electrodermal activity (EDA) monitoring, and a skin-conforming photoplethysmography (PPG) sensor where AgBioA functions dually as structural adhesive and conductive interconnect.