Formation of superhydrophobic-superhydrophilic pattern on flowerlike alumina thin film by the sol-gel method

We have prepared superhydrophobic surfaces which become superhydrophilic by heat-treatment at 500 degreesC or irradiation of UV-light. When hydrolyzed fluoroalkyltrimethoxysilane (FAS) was coated on Al2O3 gel film with a roug hness of 20 to 50 nm, the films showed superhydrophobicity and high transpa rency; the contact angle for water of the film was 165 degrees and the tran smittance for the visible light was higher than 92%. When the FAS-coated th in films were heat-treated at temperatures higher than 500 degreesC, the fi lms became superhydrophilic; the contact angle for water on the films was s maller than 5 degrees. Thin films of amorphous TiO2 or anatase TiO2 were co ated between Al2O3 gel and FAS layer, and the contact angle for water was a lso about 160 degrees. UV irradiation using high-pressure mercury lamp on t hese films resulted in the contact angle to be smaller than 5 degrees. When UV light was irradiated through a photomask, superhydrophobic-superhydroph ilic micropatterns applicable as a stamper for printing or a substrate of m icro-optical components were successfully obtained on the films.