Diapers made from silk and shrimp shells?

Harvard University

Shrilk is a new material inspired by insect cuticle that is made with components found in silk and shrimp shells. Shown here is a replica of an insect wing made with Shrilk.

By John Roach

Parents who fret over the choice between cloth and disposable diapers may soon have another option: biodegradable ones made with a new material called called "Shrilk," so named because it's made by?combining a silk protein with chitin, a hard substance commonly extracted from shrimp shells.

The Wyss Institute for Biologically Inspired Engineering at Harvard University reports that Shrilk "replicates the exceptional strength, toughness, and versatility of one of nature's more extraordinary substances ? insect cuticle."


The wonder material is billed as "a low-cost, biodegradable, and biocompatible" replacement for plastics in consumer products ? think diapers, trash bags, and packaging ? as well as a range of medical applications such as sutures and "a scaffold for tissue regeneration."

To make the material, institute researchers studied the mechanical and chemical interactions between the materials that make up many a bug's exoskeleton?? chitin, a polysaccharide polymer, and protein organized in a laminar, plywood-like structure ??and recreated the chemistry and laminar design in their lab.

The result, according to the institute, is a "thin, clear film that has the same composition and structure as insect cuticle."

Manipulations of water content in the manufacturing process allows for variations in stiffness from elastic to rigid.

In other words, the researchers turned to nature and found a material ? insect cuticle ? that provides protection, is lightweight, flexible and versatile, and then they found a way in the lab to recreate it using natural raw materials.

Material limit
Of course, like all raw materials, chitin and silk are finite, noted Javier Fernandez, a researcher at the Wyss Institute who is the lead author of a paper describing the material this week in the journal Advanced Materials.

"In the case of chitin, the limit is very high because chitin is the second most abundant polymer on earth (only surpassed by cellulose) and is present from fungus to arthropod (for example, shrimp)," he told me in an email.?

For fibroin, which is a protein created in the production of silk, the limit is lower. And it isn't readily extracted from discarded waste, such as chitin is from shrimp shells.?

At the lab scale, where the researchers are developing the material and its production, these limits aren't a problem, but "if we are proposing a new technology for the future and we want to scale the production then we're going to find it," Fernandez said.

The limit is similar to what we've already found with lumber and cellulose, which are forest products that we use to build houses and make newspaper, for example. Trees seemed super abundant and renewable until we started using more than we grew each year and ecosystems began to fray.

Engineering solutions
Scientists, however, may be able to overcome the resource limitations in the production of Shrilk with the help of genetic engineering. Chitin, for example, can be over-expressed in genetically modified microbes and fibroin has been produced in bacteria and goat milk, Fernandez said.

(Similar genetic engineering, or course, is applied to other natural resource dependent industries, including forestry where trees are engineered to grow faster for pulp and paper products, for example.)

"In the process of harvesting fibroin and chitin, growing bacteria will be the equivalent to planting trees," he noted. "To produce more of our components, we only need to promote some specific ecological cycles."

That means that future parents juggling between diapers?made with petroleum products that clog landfills, or cloth ones that consume energy and require chemicals to keep clean, might get a more sustainable option: Shrilks.

First, though, Fernandez said that he and his team need to spend more time in the lab improving their biological and fabrication methodology.

"But behind [that lab work] is a new way of thinking in technological development where things should be produced and integrated in natural cycles."

More on futuristic bioinspired materials:


John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

Where nations used to compete to get into space, now the competition focuses on private businesses, pouring hundreds of millions of dollars into next-generation spaceships. Msnbc.com science editor Alan Boyle reports from inside the rocket factories on the future of spaceflight.

Source: http://futureoftech.msnbc.msn.com/_news/2011/12/15/9470925-diapers-made-from-silk-and-discarded-shrimp-shells

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