Superhydrophobic silica surfaces: fabrication and stability

We report a simple method to make hybrid or pure silica micropatterns at the surface of a substrate based on the combination of sol-gel process and nano-imprint lithography. The silica patterns can be easily designed during the photolithographic step and functionalized with a vapor phase deposition of fluorosilane molecules to obtain superhydrophobic surfaces. Benefiting from the properties of silica, our superhydrophobic patterns can withstand elevated temperatures and show interesting optical properties. These surfaces can be used for thermal transfer applications or microfluidic devices for example to limit noise in fluorescence measurements for biological applications. In connection to the fabrication of superhydrophobic surfaces, the organization of patterns (period of grating) and height of patterns were tested, and the stability of the Cassie-Baxter state studied. The transition can be described on a wide range of tested parameters by the sliding threshold where the control of side wall angle of patterns and chemistry of surface is essential.