Harvard University, March 3, 2014 - Researchers at Harvard's Wyss Institute have developed a method to carry out large-scale manufacturing of everyday objects — from cell phones to food containers and toys — using a fully degradable bioplastic isolated from shrimp shells. The objects exhibit many of the same properties as those created with synthetic plastics, but without the environmental threat. It also trumps most bioplastics on the market today in posing absolutely no threat to trees or competition with the food supply. The advance was reported online last week in Macromolecular Materials & Engineering.
Most bioplastics are made from cellulose, a plant-based polysaccharide material. The Wyss Institute team developed its bioplastic from chitosan, a form of chitin, which is a powerful player in the world of natural polymers and the second most abundant organic material on Earth. Chitin is a long-chain polysaccharide that is responsible for the hardy shells of shrimps and other crustaceans, armor-like insect cuticles, tough fungal cell walls — and 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, for example. However, material engineers have not been able to fabricate complex three-dimensional (3D) shapes using chitin-based materials — until now.
The Wyss Institute team, led by Postdoctoral Fellow Javier Fernandez, Ph.D., and Founding Director Don Ingber, M.D., Ph.D., 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.
"There is an urgent need in many industries for sustainable materials that can be mass produced," Ingber said. Ingber is also the Judah Folkman Professor of Vascular Biology at Boston Children's Hospital and Harvard Medical School, and Professor of Bioengineering at the Harvard School of Engineering and Applied Sciences. "Our scalable manufacturing method shows that chitosan, which is readily available and inexpensive, can serve as a viable bioplastic that could potentially be used instead of conventional plastics for numerous industrial applications."
After fully characterizing in detail how factors like temperature and concentration affect the mechanical properties of chitosan on a molecular level, Fernandez and Ingber 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.
This advance validates the potential of using bioinspired plastics for applications that require large-scale manufacturing, Fernandez explained. 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.
The Wyss Institute for Biologically Inspired Engineering at Harvard University (http://wyss.harvard.edu) uses Nature's design principles to develop bioinspired materials and devices that will transform medicine and create a more sustainable world.
Cover photo: Alaskan shrimp. This image is in the public domain because it contains materials that originally came from the U.S. National Oceanic and Atmospheric Administration, taken or made as part of an employee's official duties.