Preparation of biobased wrinkled surfaces via lignification-mimetic reactions and drying: a new approach for developing surface wrinkling

Abstract

A simple and green approach to surface wrinkling via a lignification-mimetic reaction and drying is reviewed. A skin layer is synthesized on a chitosan (CS) film via immersion in a methanol solution containing a phenolic acid (PH) and a subsequent surface reaction with horseradish peroxidase (HRP), mimicking wood lignification. A surface relief with micron-scale wrinkles is formed upon drying as a result of inhomogeneous shrinkage. The wrinkle size of this system is predominately determined by the hardness of the skin layer, and the hardness in turn can be controlled by varying both the molecular structure of the PH and the immersion temperature. The crosslinking structure in the skin is composed of ionic bonding between the CS and an oligophenolic residue generated by the HRP-catalyzed surface reaction on the CS, and the quantity of the ionic bonds determines the skin hardness. Furthermore, the wrinkle direction can be highly controlled by the external stress during drying. Notably, this is a totally biobased system that involves green materials and processes. Recently, we have developed a simple and green approach to surface wrinkling via lignification mimetic reaction and drying. A skin layer is synthesized on a chitosan film via immersion in a methanol solution containing a phenolic acid and subsequent surface reaction by horseradish peroxidase, mimicking wood lignification. A surface relief with micron-scale wrinkles is formed upon drying and as a result of inhomogeneous shrinkage. This focus review overviews this innovative approach and its detailed mechanism.