Bioinspired Ultrahigh Water Pinning Nanostructures

Rose petal mimetic surfaces with ultrahigh water pinning forces have been fabricated via nanoimprinting process onto three different polymer films. Water pinning forces ranging from 104 to 690 mu N are obtained on free-standing polycarbonate films with imprinted nanostructures. Through a systematic variation of the surface structures, this study provides experimental evidence that an ultrahigh water pinning force can be achieved by combining two surface topographical designs: (1) conical- or parabolic-shaped nanoprotrusions and (2) isotropic and continuous nano-protrusions. These design criteria ensure that a continuous solid liquid contact line is achieved and provide a rule-of-thumb to engineer surfaces with tunable water pinning forces. The ultrahigh water pinning film is further demonstrated to mitigate the "coffee ring" effect, a phenomenon associated with nonuniform deposition from a drying solute-laden liquid droplet.