Photoswitching between Water-Tolerant Adhesion and Swift Release by Inverting Liquid Crystal Fingerprint Topography

Abstract

Although switchable adhesive surfaces are important and desirable for soft robotics, it is still challenging to replicate nature's switchable adhesion capability on artificial surfaces, especially for underwater applications. Here polymeric coatings with fingerprint topographies that are capable of switching the surface adhesion upon light illumination are reported. This is achieved via a synergistic combination of surface topographical inversion and spatially selective distribution of adhesive polymers. The surface topographical inversion is accomplished by the anisotropic deformation of the fingerprint-configured liquid crystal network (LCN) coating upon light-controlled order parameter modulation. Adhesive and nonadhesive polymers are spatial-selectively arranged on top of the LCN coating following the alternating homeotropic and planar domains, respectively, where liquid crystal mesogens are orthogonally aligned. The adhesive part is composed of a water-tolerant adhesive polymer with 3,4-dihydroxy-l-phenylalanine (catechol) groups inspired by mussel byssus. This report presents a dynamic surface with locally alternating nonadhesive indented areas and adhesive elevated areas where the topographical positions can be dynamically changed with light illumination which can serve as smart skins for robotic applications.