Constructing a superhydrophobic surface on polydimethylsiloxane via spin coating and vapor-liquid sol-gel process

In this study, a superhydrophobic surface on polydimethylsiloxane (PDMS) substrate was constructed via the proposed vapor-liquid sol-gel process in conjunction with spin coating of dodecyltrichlorosilane (DTS). Unlike the conventional sol-gel process where the reaction takes place in the liquid phase, layers of silica (SiO₂) particles were formed through the reaction between the reactant spin-coated on the PDMS surface and vapor of the acid solution. This led to the SiO₂ particles inlaid on the PDMS surface. Followed by subsequent spin coating of DTS solution, the wrinkle-like structure was formed, and the static contact angle of the water droplet on the surface could reach 162° with 2° sliding angle and less than 5° contact angle hysteresis. The effect of layers of SiO₂ particles, concentrations of DTS solution and surface topography on superhydrophobicity of the surface is discussed.