Superhydrophobic surfaces templation

Another widely used approach in this area is a sol-gel process. In order to create surface roughness after deposition of thin films, a secondary component is included in the sol-gel deposition process which can be removed later by dissolution in hot water or sublimation. The removal of the secondary components gives porous structures. Subsequent lluorinated silane coating can render these sol-gel processed films superhydrophobic [81-83]. Microporous structures can be created through phase separation of organic polymer solutions and then used as a template for sol-gel processing of porous silica substrates. Ruorosilane treatment of these substrates produces superhydrophobic surfaces [84]. 

Figure 1 Typical superhydrophobic surface structure fabricated by templating method (A) replica of Co/ocas/a-like leaf surface on PDMS template (Singh et al., 2007), (B) a microporous pattern of polyvinylidene fluoride film (Li et al., 2006), (C) superhydrophobic hair shaped polymer surface grown through an AAO template (Zhang et al., 2006) and (D) water droplet resting on a polymer hot-press transferred pattern (Bormashenko et al., 2006). PDMS, polydimethylsiloxane AAO, aluminum oxide. Images reprinted with permission from (A, B) Elsevier, Copyright2007and2006 respectively, (C, D) American Chemical Society, Copyright2006.

Peng, R, Ke, Q., Zhou, G.,Tang,T., 2013. Fabrication ofmicrocavity-array superhydrophobic surfaces using an improved template method.. Colloid Interface Sci. 395,326. 

According to Wenzel s equation, obviously, high roughness can enhance the hydrophilicity of a native hydrophilic surface. In our study, such porous film is much rougher than relatively flat surface obtained without using template, so this model can explain why our as-synthesized films show superhydrophilicity with a CA about 5°. After modification with a lower surface free energy material, the air can be trapped in such ordered pore array, and hence a composite surface composed of air and pore array is formed. The measurements show that the surface is superhydrophobic with water CA of 154°. In this case, the Cassie equation is applicable. Based on a simplified model, as schematically illustrated in Fig. 6, the relationship... 

The inset of Fig. 13b shows the water droplet on the surface of the Au particle array after modification with 1-hexadecanethiol. It exhibits superhydrophobicity with a CA 162°. On the contrary, CAs for the smooth Au film, prepared by vacuum physical vapor deposition on ITO substrate, and rough Au film, prepared by electrodeposition on ITO substrate without template, are 94° and 122°, respectively. 

Q. F. Xu, B. Mondal and A. M. Lyons, Fabricating superhydrophobic polymer surfaces with excellent abrasion resistance by a simple lamination templating method, ACS Appl. Mater. Interfaces, 3,3508-3514 (2011). 

Feng, J., Lin, E, Zhong, M., 2010. Stretching-controUed micromolding process with etched metal surfaces as templates towards mass-producing superhydrophobic polymer films. Macromol. Mater. Eng. 295. 

---