Tuning the wettability of an aluminum surface via a chemically deposited fractal dendrite structure

We have developed a straightforward method to tune the wettability of an aluminum substrate within a contact angle (CA) range from 2 degrees to 170 degrees by chemical deposition in CuCl2 solution and fluoroalkylsilane (FAS) modification. The CA of the as-deposited surface decreases with deposition time due to the growth of fractal copper dendrites, which enhance the surface roughness significantly. After subsequent modification with FAS, a superhydrophobic surface with CA 170 degrees and sliding angle less than 5 degrees has been obtained. With the increase of CA, the maximum spreading of water droplets is reduced. A bouncing behavior is observed for droplets impinging on the superhydrophobic substrate, suggesting its potential application as a self-cleaning surface.