'Shrilk' Mimics Insect Exoskeleton

A new material that mimics the exoskeleton of insects has the strength and toughness of aluminum, but weighs half as much. "Shrilk," developed by a research team at Harvard University's Wyss Institute for Biologically Inspired Engineering, is also low-cost, biodegradable, and biocompatible.

Shrilk has possible applications in medicine for wound dressings, and as a possible alternative to packaging that degrades quickly. It was developed by Javier G. Fernandez, PhD, a postdoctoral fellow at the institute, and Donald Ingber, MD, PhD, the institute's founding director and a professor of bioengineering at the Harvard School of Engineering and Applied Sciences.

The research team studied the mechanical and chemical interactions between the different layers of natural insect cuticle, the material that makes up an insect's exoskeleton. These layers are chitin, which is a polysaccharide polymer, and protein, organized in a laminate-type, plywood-like structure. Interactions between these two materials give the natural cuticle its unique mechanical and chemical properties.

The team then recreated the cuticle's chemistry and laminar design in the lab, engineering a thin, clear film with similar composition and structure. Shrilk is composed of chitosan derived from chitin and a fibroin protein derived from silk. Chitin, one of the most abundant polymers, is readily available in large quantities as a waste product of shrimp. Shrilk can therefore be produced for a very low cost. It can also be easily molded into a variety of complex shapes, such as tubes.

Natural insect cuticle is very tough, but also very lightweight, and thin enough to be flexible. It protects but does not add weight or bulk. It can therefore resist external chemical and physical stresses while also providing structure.