By mimicking the self-assembling microstructures that give spider silk its incredible strength, scientists at the University of Cambridge have produced a plant-based film with the strength of common single-use plastics, offering a "vegan" eco-friendly alternative to the material. The free-standing film can be colored and scaled up for industrial use, and then easily composted once its job is done.
Its fine strands might seem flimsy to us relatively large humans, but with a strength five times greater than steel by weight, spider silk has many secrets to share with the world of material science. We have seen researchers in this field take inspiration from spider silk to develop materials for more sensitive hearing aids, to encase cancer drugs for better delivery and even use it to repair severed nerves, just to list a few examples.
The University of Cambridge scientists had been studying the behavior of proteins, and as part of this, had turned their attention to the makeup of spider silk and the unique composition that affords it such great strength.
“We found that one of the key features that gives spider silk its strength is the hydrogen bonds are arranged regularly in space and at a very high density,” says study author Professor Tuomas Knowles.
The scientists then set out to recreate this process using self-assembling proteins sourced from plants instead. This began with soy protein isolate, which like all proteins, is made of polypeptide chains that can be made to self-assemble under the right conditions. Achieving this involved a mix of acetic acid and water, high temperatures and ultrasonication, to improve the solubility of the protein and make it easier to control its self-assembly into ordered structures.
“Because all proteins are made of polypeptide chains, under the right conditions we can cause plant proteins to self-assemble just like spider silk,” says Knowles.
The finished product is a set of protein structures with enhanced molecular interactions driven by hydrogen bond formation, just like in spider silk. When the solvent is removed, a water-insoluble film remains with a mechanical performance equivalent to common single-use plastics like polyethylene. And because it involves no chemical modifications to its all-natural building blocks, the material can safely degrade in home composting systems.
“Other researchers have been working directly with silk materials as a plastic replacement, but they’re still an animal product,” says co-author Dr Marc Rodriguez Garcia. “In a way, we’ve come up with ‘vegan spider silk’ – we’ve created the same material without the spider.”
The researchers have patented the technology and plan to commercialize it through spin-off company Xampla, while the research was published in the journal Nature Communications.
Source: University of Cambridge