Harvard’s Wyss Institute specializes in designing new materials and devices that mimic patterns found in living things. Their latest contribution was inspired by the versatile material found in insect cuticle, which is strong and flexible, yet remarkably lightweight.
The result was “shrilk,” a moldable, biodegradable substance derived from shrimp shells and silk that is as strong as some aluminum alloys but only half their weight.
“Shrilk could be used to make trash bags, packaging, and diapers that degrade quickly,” according to a Wyss Institute press release.1
The inventors copied the plywood-like arrangement of interconnected layers from the cuticles of arthropods like shrimp, lobsters, or insects. They arranged chitin taken from discarded shrimp shells in thin sheets sandwiched between proteins derived from silk. The cross-layering pattern doubled the overall strength.
Chitin is a sugar-based polymer that provides rigid yet flexible protection and framework for arthropods and a few other creatures.2 Experimenters had long ago defined procedures that use acid to modify and extract chitin from source cuticles like shrimp shells.3 This chitin-derivative has been extruded into an array of forms, then hardened under the influence of certain chemicals.
The shrilk engineers added the layering technique, in effect copying the plan that provided strength to the original shrimp shells, but in new shapes and thicknesses. They did not build machines that can manufacture the chitin or silk proteins produced by arthropods and worms. They merely mimicked the creatures’ strategies for layering the materials.
Taken together, at least three different and dependent levels of information are required for both insect cuticles and shrilk. First, genetic blueprints specify the suites of tiny cellular machines that manufacture and excrete chitin and silk. Second, the chitin and silk proteins are arranged according to molecular patterns that are exactly specified for their purposes. Finally, these ingredients are laid out according to an overall sheet-like strategy to become strong, flexible, and biodegradable….
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