New progress in multiscale structures construction on porous silicon (PSi) surface and it superhydrophobicity was accomplished by the research team headed by Prof. Zhang Junyan of LICP. They have fabricated papillary microstructures on mesoporous silicon film by electrochemical etching combined with subsequent surface texturing with capillary stress. Researchers have found that the preferred releasing of local capillary stress at macropore sites during pentane evaporation and the gradient variation of porosity are essential to the formation of papillary microstructures on mesoporous silicon surface. After modification with octadecene, the PSi surface with multiscale structures is superhydrophobic.

Inspired by natural species, researchers presented the idea to increase surface roughness with the synergistic effect of multiscale structures. Combined electrochemical etching with capillarity-driven surface texturing, the multiscale structures have been controlled efficiently. The method used is very useful for constructing biomimic surfaces with multiscale structures on porous films and, considering the excellent biocompatibility of PSi, the surfaces prepared may find application in microfluidics.

The research has won support from the National Natural Science Foundations of China and was published in the Chem. Commun (Chem. Commun., 2009, 4239–4241).

Surface-cracking models for porous films with homogeneous
pores (a) and heterogeneous pores (b). Both mesopores, with diameter
o10 nm (c, AFM image obtained on PSi with 10 min etching) and
macropores with diameter ca. 200 nm (d, FE-SEM image acquired on
PSi with 30 min etching) coexisted in the PSi films.

Abstract of the paper published in Chem. Commun.