Ultrathin Transformable Polymer Nanomembranes for Conformal Bioelectronic Interfaces

Soft bioelectronic devices require not only high-performance electronic materials, but also mechanically compliant and stable interfaces with wet, soft, and dynamically moving biological tissues. However, conventional polymer-based bioelectronic devices often suffer from a mismatch between device rigidity and tissue softness, which can limit long-term conformal contact and stable signal recording. Here, we present an ultrathin transformable polymer nanomembrane for imperceptible and high-performance bioelectronic interfaces. The system integrates a high-performance mixed ionic–electronic conducting conjugated polymer, P(g2T2-Se) (μC* = 1034 F cm^-1V^-1s^-1), with a tissue-adhesive alginate-catechol hydrogel layer to form an ultrathin bilayer organic electrochemical transistor platform (~350 nm total thickness). Selenophene substitution in the conjugated polymer enhances backbone planarity, electrolyte wettability, and mixed ionic–electronic transport, leading to improved OECT performance. Meanwhile, the alginate-catechol layer provides strong interfacial adhesion and enables a dry-to-wet mechanical transformation: the membrane is self-supporting in the dry state but becomes soft and conformal upon hydration. Owing to its ultrathin architecture and tissue-adhesive interface, the device can form conformal contact with biological tissues while maintaining stable transistor operation under mechanical deformation. We further demonstrate reliable in vivo electrophysiological recording from wet and moving tissues, including the heart, muscle, and brain, in rat models. This work highlights a functional polymer design strategy that combines high-performance conjugated polymer electronics with transformable and adhesive soft interfaces, offering a promising route toward conformal, stable, and tissue-integrated bioelectronics.