One-step wet electrospinning of graphene oxide-coated fibrous interfaces for flexible humidity sensing

Abstract In this work, we use GO-assisted wet electrospinning/coagulation to investigate how polymer-matrix chemistry controls GO interfacial organization and humidity-responsive behavior in flexible fibrous coatings directly integrated on interdigitated electrode chips. The study focuses on the direct implementation of this approach for humidity-sensing interfaces and on the matrix-dependent organization of GO within PLA- and PVDF-based fibrous coatings. The process relies on electrospinning polymer solutions into a coagulation bath containing dispersed GO, thereby enabling fiber precipitation, solvent–non-solvent exchange, and interfacial GO adsorption to occur simultaneously. This enables the formation of flexible micro/nanofibrous coatings that are consistent with preferential GO localization at the fiber surface, yielding matrix-dependent GO-rich interfacial architectures, ranging from a sleeve-like GO-rich layer in PLA to discontinuous/partially embedded GO-rich domains in PVDF without post-deposition coating treatments. The wet electrospinning route yielded porous fibrous architectures via diffusion-induced phase separation (DIPS), while the GO-rich outer layer introduced hydrophilic and electrically active domains that interact strongly with water vapor. When integrated onto interdigitated Au chips, only the GO-containing systems showed a reproducible increase in resistance from 40% RH onward, achieving normalized responses of approximately 4%, 8%, and 16% at 40, 60, and 80% RH, respectively, over three consecutive cycles. The sensing behavior appears to be governed primarily by the presence and surface chemistry of GO, and it was interpreted in terms of water adsorption, GO swelling, modulation of interflake spacing and tunneling barriers, and proton-assisted transport through hydrogen-bonded networks. Beyond humidity sensing, the proposed approach provides a versatile framework for engineering multifunctional polymer/GO interfaces by coupling process-induced hierarchical structuring with surface-confined nanocarbon functionality.