Facile transition of surface wettability in hierarchical silica framework: from Wenzel to Cassie-Baxter regime

Facile control of surface wettability is demonstrated by introducing a scalable and cost-effective method using candle soot as a hierarchical template. Through soot deposition, silica sol-gel coating, calcination, and self-assembled monolayer (SAM) treatment, surfaces with tunable wettability from superhydrophobic (contact angle >150°) to superhydrophilic (contact angle = 0°) were fabricated. The hierarchical roughness introduced by soot deposition was instrumental for achieving radically biased surface wettability. Silica coating transformed the soot-coated surfaces to superhydrophilic by increasing surface energy, while calcination created a porous silica framework. SAM treatment restored superhydrophobicity by lowering surface energy and re-establishing the Cassie-Baxter wetting regime. Optimized soot deposition times retained transparency, ideal for optical applications, and mechanical stress testing caused a transition from Cassie-Baxter to Wenzel regime, exhibiting pinning of water droplet. This versatile approach enabled designed surface wettability depending on target purposes.

Graphical abstract

Versatile surface wettability control with candle soot template.