A bioinspired self-pumping Janus interface for wet-adhesive epidermal ECG monitoring

A bioinspired self-pumping Janus paper electrode was developed for wet-skin ECG. • Asymmetric wettability (127°/28°) enabled directional liquid transport within 10 s. • The interface combined wet adhesion, high breathability, and conductive stability. • Stable ECG signals were acquired during sweating, walking, and brief submersion. • The platform offers active liquid management for wet-stable epidermal bioelectronics. Wet epidermal electrocardiogram (ECG) interfaces commonly suffer from the coupled deterioration of adhesion, breathability, and signal fidelity under sweating and motion. Here, we report a self-pumping Janus paper electrode comprising a skin-contacting hydrophobic polydimethylsiloxane (PDMS)-based adhesive layer, a mechanically compliant interlayer, and an outer hydrophilic carbon-nanotube (CNT)-doped porous paper layer. A coupled wettability and pore-size gradient promotes directional drainage of interfacial liquid away from the skin–electrode contact. The interface exhibits asymmetric wettability (127°/28°), directional liquid transport within 10 s, measurable water uptake, adhesion on moist skin, water-vapor permeability, and stable ECG acquisition during sweating and walking. Distinct from Janus liquid-transport materials or wet-adhesive ECG interfaces that primarily address either directional wetting or adhesion, this work presents a coupled-gradient capillary-rectification strategy in which wettability and pore-size gradients generate an asymmetric capillary-pressure landscape. The paper-based interface integrates wet adhesion, water-vapor permeability, liquid management, and ECG signal acquisition, providing a strategy for stable wet-skin ECG monitoring under the tested conditions.