Hydrophobic/superhydrophobic oxidized metal surfaces showing negligible contact angle hysteresis

Dynamic wettability of oxidized metal (aluminum and titanium) surfaces could be tuned by chemical vapor deposition (CVD) of 1,3,5,7-tetramethylcyclotetrasiloxane (D-H(4)). This facile CVD method produces not only monomeric layers but also particulate films by changing the CVD temperature, resulting in a marked difference in the final wetting properties. In the samples prepared at 80 degrees C for similar to 3 days, D-H(4) layers with thicknesses of similar to 0.5 nm were formed on the surfaces without discernible change in surface morphology, as evidenced by X-ray photoelectron spectroscopy and atomic force microscopy. After this 14 monomeric layer formation, the hydrophilic oxidized aluminum and titanium surfaces became hydrophobic (advancing/receding water contact angles (0(A)/0(R)) 102-104 degrees/99-102 degrees) showing essentially negligible contact angle hysteresis. Performing CVD of D-H(4), at 180 degrees C for similar to 1 day produced opaque film with particulate morphologies with diameters in the range of 500 nm to 4 mu m observed on the surfaces. This geometric morphology enhanced the surface hydrophobicity (0(A)/0(R) = 163 degrees/160-161 degrees). Droplets on these negligible-hysteresis surfaces moved very easily without pinning. (C) 2010 Elsevier Inc. All rights reserved.