Bioinspired Catechol-PEG Functionalized PVDF Nanofiber Membranes with Hydrophilicity-Adhesion Synergy for Reliable Skin-Conformal Sweat Sensing

Wearable sweat sensors are emerging as transformative noninvasive platforms for real-time physiological monitoring. However, persistent challenges regarding dynamic skin conformability, reliable adhesion, efficient sweat uptake/transport, and biosafety impede clinical translation. Herein, we developed hydrophilic-adhesive polyvinylidene fluoride (PVDF) nanofiber membranes via a bioinspired modification strategy for sweat sensor construction. Catechol-functionalized polyethylene glycol copolymer (catechol-PEG) was synthesized through epoxy-amine ring-opening polymerization between poly(ethylene glycol) diglycidyl ether (PEGDE) and dopamine, followed by integration into PVDF electrospinning solutions to fabricate composite membranes. The composite membranes demonstrate robust reusable adhesion maintaining conformal skin contact on curved surfaces during movement, coupled with instantaneous superhydrophilicity reducing water contact angles from 135° to 0°. Remarkably, hydration enhances adhesive strength compared to dry conditions, ensuring stable interfacial bonding during perspiration. Furthermore, catechol-PEG endows the membranes with potent antibacterial activity (>98.6% and 97.7% inhibition against <i>S. aureus</i> and <i>E. coli</i>, respectively) and significantly improves air permeability (5.4-fold enhancement). Sensors constructed on this multifunctional substrate exhibit efficient sweat wicking for continuous biomarker analysis and maintain stable epidermal adhesion during intense physical activity. Human trials with athletes validated reliable multiplexed detection of sweat biomarkers, including pH and electrolytes (Cl^-, Ca²⁺). This integrated material system establishes a versatile platform for next-generation wearable diagnostics, effectively resolving critical limitations in epidermal monitoring technologies.