Regenerated Silk Fibroin Film with a Robust Functional Surface Physically Modified by Pollen Grains

Silk fibroin regenerated from silkworm cocoons has provided a biocompatible and environmentally friendly platform for various technological applications. The surface of regenerated silk fibroin prepared in bulk or film form is inherently hydrophilic, so it is important to modify the surface to achieve the desired level of wettability. However, traditional chemical approaches do not guarantee robust surfaces that can withstand a variety of extreme environments. Here, we present a new strategy to physically modify the surface of silk fibroin films by imprinting the microstructure of the pollen surface. The elastomeric mold, consisting of a pollen monolayer with a spike-shaped surface, is replicated into a wafer-scale silk fibroin film through a series of imprinting processes. The resulting pollen-imprinted silk fibroin film exhibits a high contact angle of 126° without any chemical treatment. The contact angle does not decrease after repeated washing with detergent due to the physically modified surface. Additionally, the unique hierarchical topology of the pollen-derived surface allows the film to exhibit excellent optical scattering, ensuring its applicability as functional optical films. In this presentation, we will show the potential applications based on the unusual properties of silk films with robust functional surfaces.