Geometric structure modification in cellulose acetate nanofibers and its impact on liquid resistance/repellency

Surface modification—altering geometric structures or surface energy—is a key factor in improving liquid resistance/repellency on a solid surface. In particular, roughness from geometric structures provides void spaces that enhance energy barriers in nanofibers that a liquid droplet should overcome to penetrate, thus preventing the transition of a liquid drop from the Cassie–Baxter state to Wenzel state. In this work, the design of a geometric structure that performs highly in liquid resistance/repellency was proposed by extending the Cassie–Baxter model into cellulose acetate (CA) nanofibers, entrapping SiO₂ nanoparticles, and examining the impact of void spaces created by the entrapped SiO₂ into nanofibers in prediction and experiment. The extended Cassie–Baxter equation was simplified using H*, which is characterized by T_np. The prediction and measurement of the apparent contact angle \( \theta_{nf} \) in CA-SiO₂ nanofabrics showed good agreement, and the results emphasized the role of void space in improving liquid resistance/repellency while minimizing chemical treatments for altering surface energy and geometric structure.