Water repellency of large-scale imprinting-assisted polymer films

We report that the water repellency of polymeric film surfaces can be simply tuned by pressing softened polymer films into porous anodized aluminum oxide (AAO) templates. Highly-dense nano-pillars and nano-hairs on the polymer surfaces are reproduced via physically or chemically separating the AAO templates from the impressed polymer films. The resulting polymeric nano-textures show various aspect ratios (ARs) between height and cross-sectional diameter (from 2 to 130), depending on the viscoelastic response of the polymer chains during hot AAO pressing and the subsequent separation procedures. The water contact angle values on the nano-textured polymer films considerably changed from 91° to 160° with an increase in AR. Using hot pressing and physical detachment of a porous AAO-covered Al cylinder roller, we successfully demonstrated the potential for large-area fabrication of superhydrophobic polymer films with characteristics that are similar to lotus leaves. [Figure not available: see fulltext.].