One-step eccentric side-by-side electrospraying of Janus particle coatings on cotton in an ethanol–water system for multifunctional finishing

Abstract

Conventional multifunctional cotton finishing is often limited by multistep workflows, whereas single-bath formulations may suffer from component incompatibility and binder-induced masking of surface-active additives. Here, a one-step eccentric side-by-side electrospraying strategy in a benign ethanol–water system was developed to fabricate Janus particle coatings on cotton. An ethanol-diluted industrial finishing formulation, used for cooling or hydrophobic surface regulation, was co-electrosprayed with an aqueous ZnO nanoparticle-loaded waterborne polyurethane (ZnO–WPU) dispersion through an eccentric dual-channel nozzle. Electrostatic simulation showed that the eccentric geometry generated a less laterally split near-outlet field distribution and reorganized the force topology from lateral divergence to interfacial convergence, thereby promoting coordinated co-emission. Multiscale characterization by EDS, FTIR, and TEM, together with dual-dye confocal fluorescence imaging, supported Janus-type spatial segregation rather than homogeneous mixing, with the ZnO–WPU-rich domain serving primarily as an anchoring phase while also providing antibacterial activity and UV shielding, and the functional domain governing cooling or hydrophobic wettability. The treated fabrics achieved strong initial cooling performance (Qmax ≥0.22 W·cm−2) or superhydrophobicity (static water contact angle >150°), while maintaining >99% antibacterial efficacy against Escherichia coli and Staphylococcus aureus after washing exposure equivalent to 10 domestic laundering cycles. The ZnO-containing coatings also provided tunable UV protection, with UPF values up to 46.54. These multifunctional effects were obtained at low add-on weight with negligible visual change and only minor reductions in air permeability, demonstrating a practical route for integrating anchoring and surface functionality in a single step using industrially available formulations under mild processing conditions. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.