Researchers at Harvard's Wyss Institute for Biologically Inspired Engineering, Boston, MA, say that they have developed a method for large-scale manufacturing of everyday objects using a fully degradable bioplastic that’s been isolated from shrimp shells.

Chitosan is commercially produced from chitin, the structural element in shrimp exoskeletons. (Credit: NOAA)

While the objects exhibit many of the same properties as those created with synthetic plastics, the environmental threat is lessened considerably, and it poses no threat to plants or competition with the food supply.

The Wyss team formed its bioplastic from chitosan, a form of chitin, a long-chain polysaccharide responsible for the shells of shrimps and other crustaceans, armor-like insect cuticles, tough fungal cell walls, and even flexible butterfly wings.

The majority of available chitin in the world comes from discarded shrimp shells, and is either thrown away or used in fertilizers, cosmetics, or dietary supplements. However, material engineers had not previously been able to fabricate complex 3D shapes using chitin-based materials.

They say that they have developed a new way to process the material so that it can be used to fabricate large, 3D objects with complex shapes using traditional casting or injection molding manufacturing techniques. What’s more, their chitosan bioplastic breaks down when returned to the environment within about two weeks, and it releases rich nutrients that efficiently support plant growth.

After fully characterizing in detail how factors like temperature and concentration affect the mechanical properties of chitosan on a molecular level, the researchers honed in on a method that produced a pliable liquid crystal material that was just right for use in large-scale manufacturing methods, such as casting and injection molding.

They also found a way to combat the problem of shrinkage, where the chitosan polymer fails to maintain its original shape after the injection molding process, by adding wood flour, a waste product from wood processing.

The next challenge is for the team to continue to refine their chitosan fabrication methods so that they can take them out of the laboratory, and move them into a commercial manufacturing facility with an industrial partner.

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