Experimental investigation of superhydrophobic properties of the surface constructed by nanoparticles

Two kinds of micro- and nano-structural surfaces were constructed with hydrophobic nanoparticles(HNPs) directly. One of the surfaces was formed by compressing the nano powder to a smooth slice I the other was made by adsorbing the nanoparticles on the surface of rock wafer. The contact angles between water drops and the surfaces were measured and the rolling process of a water drop on the nanoparticles-adsorbed rock surface was pictured. The scanning electron microscope(SEM) was used to observe the microstructure of these surfaces also. The results show that the inorganic nanoparticles modified by weak hydrophobic material could have strong hydrophobic property, even though it was strongly hydrophibic initially. The measured contact angles of water drop on the nanoparticle-adsorbed rock surface are always greater than 120 degrees and the rolling angles are less than 7 degrees. These data means that these surfaces are superhydrophobic apparently. The SEM pictures show that these surfaces are air-solid compound interfaces with irregular micro- and nano-structure. It is these special structures that lead to the formation of superhydrophobic surfaces, which are in agreement with the Cassie-Baxter model.