One-step modification method to fabricate wettability patterns on aluminium substrate

Since there is currently no method to selectively fabricate superhydrophobic regions on superhydrophilic surfaces of metal substrates, wettability patterns on metal substrates are prepared via the three-step technique including superhydrophilic, superhydrophobic and selectively superhydrophilic modifications. Here, an innovative method that can selectively lower surface energy of superhydrophilic surfaces, and thereby makes it more convenient to fabricate the wettability patterns, is proposed. Chemical etching is used to formulate micro/nanoscale rough structures and fabricate superhydrophilic aluminium (Al) surface, which is then covered by patterned mask whose main composition is siloxane. Removing the mask after 80 degrees C water bath heating for 20 s, the covered Al surface has been modified to become superhydrophobic (contact angles >165 degrees, sliding angles <1.5 degrees), while the uncovered region is still superhydrophilic, and wettability patterns are therefore obtained. Fourier transform infrared spectrophotometer and Raman spectra indicate that the change of wettability is induced by hydrophobic groups on the modified surfaces. The superhydrophobic surfaces fabricated by this method have excellent high-temperature resistance. The method proposed is simple, rapid and environmental-friendly.