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.