Nanosphere Lithography of Chitin and Chitosan with Colloidal and Self-Masking Patterning.

Dennis LaJeunesse,Kyle Nowlin,Rakkiyappan Chandran

doi:10.3390/polym10020218

Abstract

Complex surface topographies control, define, and determine the properties of insect cuticles. In some cases, these nanostructured materials are a direct extension of chitin-based cuticles. The cellular mechanisms that generate these elaborate chitin-based structures are unknown, and involve complicated cellular and biochemical “bottom-up” processes. We demonstrated that a synthetic “top-down” fabrication technique—nanosphere lithography—generates surfaces of chitin or chitosan that mimic the arrangement of nanostructures found on the surface of certain insect wings and eyes. Chitin and chitosan are flexible and biocompatible abundant natural polymers, and are a sustainable resource. The fabrication of nanostructured chitin and chitosan materials enables the development of new biopolymer materials. Finally, we demonstrated that another property of chitin and chitosan—the ability to self-assemble nanosilver particles—enables a novel and powerful new tool for the nanosphere lithographic method: the ability to generate a self-masking thin film. The scalability of the nanosphere lithographic technique is a major limitation; however, the silver nanoparticle self-masking enables a one-step thin-film cast or masking process, which can be used to generate nanostructured surfaces over a wide range of surfaces and areas.

Highlights

The surfaces of many insects are decorated with nanostructure topographies that control and determine specific physical and chemical properties
We demonstrate the generation of a nanostructured surface in a biopolymer—in this case, either the chitin-mats derived from an insect wing, or a thin film composed of chitosan
To determine whether a purified chitin scaffold could serve as a substrate for colloidal/nanosphere lithography, we prepared a purified chitin scaffold from a wing of the periodic 17-year cicada Brood II

Summary

Introduction

The surfaces of many insects are decorated with nanostructure topographies that control and determine specific physical and chemical properties. Insect cuticles are complex natural composite materials that are composed of a polysaccharide chitin fiber network and a matrix of proteins and lipids, and can potentially form through complex interactions during cuticle deposition [6,7] While many of these nanostructures in insect cuticles are surface features composed of a lipid–protein matrix, in the case of the dog day cicada (Tibicens species), the nanostructured surface is, in part, controlled by deeper extensions of the underlying chitin exoskeleton. This demonstrates that, in some cases, the nanoscale organization of chitin assists in the formation of nanoscale topology [4]. The initial step of the NSL process involves the masking of a Polymers 2018, 10, 218; doi:10.3390/polym10020218 www.mdpi.com/journal/polymers

Methods

Results

Conclusion