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Nature has come up with many clever designs for materials with superlative properties. By combining two natural materials that boast excellent mechanical traits, wood and spider silk, researchers have made a material that could be a possible sustainable alternative to plastic.
The new composite, reported in the journal Science Advances, comes from could be used for medical implants, sutures, textiles, and packaging. But unlike the plastics that would normally be used for those products, the material is biodegradable and is not made from petroleum.
Spider silk is well known for being five times as strong as steel by weight while being very flexible. The cellulose fibers found in wood, on the other hand, are extremely stiff and tough, that is, they take a lot of force to crack.
Researchers at Aalto University wanted to combine these properties to make a material that is stiff yet strong and flexible, a combination that is extremely hard to find.
They started with birch wood pulp and broke it down to make tiny microscopic cellulose fibers, which they aligned to make a stiff scaffold. Then they disperse these in spider silk proteins, which act like an adhesive and hold them together in a soft matrix.
The spider silk proteins they use are not extracted from spiders. Instead, the researchers first made synthetic DNA that mimics the spider’s silk protein-producing genes. Then they insert the DNA into bacteria that can then produce the protein in large enough quantities.
“Our work illustrates the new and versatile possibilities for protein engineering,” said bioproducts and biosystems researcher Pezhman Mohammadi in a press release. “In the future, we could manufacture similar composites with slightly different building blocks and achieve a different set of characteristics for other applications.”
Source: Pezhman Mohammadi et al. Biomimetic composites with enhanced toughening using silk-inspired triblock proteins and aligned nanocellulose reinforcements. Science Advances, 2019.