Nanostructured Transformative Skin: From Instability to Function

X. Zhao
Duke University, US

Keywords: nanostructured coatings

Summary:

As human beings age, our skins develop wrinkles and folds – an undesirable feature that has fueled a multi-billion-dollar skin care industry. Conversely, many animals such as cephalopods can reversibly create skin patterns to match surrounding textures for active camouflage. Besides skins on animals and plants, thin films coated on various engineering objects are also frequently subject to diverse modes of instabilities including wrinkles, creases, delaminated buckles, period-doubles, localized ridges, folds, and crumples with length scales ranging from nanometers to meters. This talk will first present a unified model that can predict various modes of instabilities and patterns on skins of animals and surfaces of engineering objects across multiple length scales ranging from nanometers to meters. By adopting the Maxwell stability criterion, we model the film-substrate structures as a thermodynamic system, and quantitatively predict the initiation and evolution of all modes of surface instabilities by mapping free-energy landscape of the system. We will then discuss novel transformative applications of surface instabilities at nanoscale such as tunable superhydrophobicity and on-demand stem-cell alignment by seeking bioinspirations.