Superhydrophobic, Low-Hysteresis Patterning Chemistry for Water-Drop Manipulation

A method for preparing superhydrophobic surfaces containing guiding lines that control water motion is described. The background surfaces exhibit contact angles of θA/θR = 173°/171°, and the guiding lines are also hydrophobic (θA/θR = 104°/102°). The low-contact-angle hysteresis allows facile water motion. The sequence of steps used to prepare these surfaces is central to their success, is designed to minimize defects, and involves only two inexpensive and fluorine-free reagents: methyltrichlorosilane and dimethyldichlorosilane. Examples of patterned surfaces that direct water motion are described. The disparity in receding contact angles is identified as the key parameter for guided motion.