- Cambridge researchers have created a polymer film inspired by a spider’s web
- His new energy-efficient method uses a by-product of soybean oil production
- Plant-based film being tested in food packaging such as sandwich containers
Scientists say a new vegan sustainable film could replace single-use plastics in many consumer products.
The film, made at the University of Cambridge, is inspired by spider silk, one of the strongest materials known to nature.
It has the strength of man-made synthetic polymers in plastic bags and film wraps, but decomposes completely naturally without harming the environment.
The new product will be commercialized by the University of Cambridge spin-out company Xampla, which is developing replacements for single-use plastics and microplastics.
Xampla will introduce a range of single-use sachets and capsules later this year that could replace plastics used in everyday products like dishwasher tablets and laundry detergent capsules – many of which still have separate plastic wrappers. come in.
The firm is also testing plant-based film in food packaging such as sandwich containers and salad boxes.
Film developed by Cambridge spin-out company Xampla, featured here in food packaging, dishwasher tablets and laundry detergent capsules
Why are spider webs so strong?
The strength of biological materials like spider silk lies in the configuration of structural proteins, which contain small groups of weak hydrogen bonds that work cooperatively to resist the force and dissipate energy.
This structure makes a lightweight natural material as strong as steel, even though the ‘glue’ of hydrogen bonds that hold spider silk together at the molecular level is 100 to 1,000 times weaker than the mighty glue of steel’s metallic bonds. is.
It is also working on developing edible films, which can be used for applications such as the oral delivery of drugs.
Non-fading ‘structural’ paint can also be added to polymers, and can also be used to make water-resistant coatings.
Experts claim that the production method can be scaled up to an industrial scale.
Study author Rodriguez García at the University of Cambridge said, ‘Other researchers are working directly with silk materials as a replacement for plastics, but they are still an animal product.
‘In a way we have come up with “vegan spider silk” – we have made a single material without the spider.’
The material can be composted at home, while other types of bioplastics require industrial composting facilities to degrade.
It also requires no chemical modification to its natural building blocks, so that it can degrade safely in most natural environments.
The material was created using a new approach to assemble plant proteins into silk-mimicking materials at the molecular level.
Spiders are master builders, weaving silk threads into intricate webs that serve as the spider’s home and hunting grounds.
Xampla will introduce a range of single-use pouches to hold food items (pictured) and cleaning products this year
Spider webs are as strong as steel, even though the ‘glue’ of hydrogen bonds that hold spider silk together at the molecular level is 100 to 1,000 times weaker than the mighty glue of steel’s metal bonds.
The researchers became interested in why materials like spider silk are so strong when they have such weak molecular bonds.
Study author Professor Tumas Knowles at Cambridge said: ‘We found that one of the key characteristics that gives spider silk its strength is that the hydrogen bonds are arranged regularly in space and at very high densities.
The team began by looking at how to replicate this regular self-assembly in other proteins.
Researchers create film by mimicking properties of spider silk, one of the strongest materials in nature
Polymers and Monomers
Most plastics are made from chains of polymers, hydrogen and carbon, derived from petroleum products such as crude oil.
Polymers are made up of short strands called monomers.
Due to the additives added to many plastics, they cannot be reused, making them difficult to dispose of because the monomers cannot separate from them.
Any replacement of plastic requires another polymer.
The team replicated the structures found on spider silk using soy protein isolate (SPI), which is readily available as a by-product of soybean oil production.
Proteins have a tendency for molecular self-organization and self-assembly.
“Since all proteins are made up of polypeptide chains, we can self-assemble plant proteins, like spider silk, under the right conditions,” Knowles said.
‘In a spider, the silk protein dissolves in an aqueous solution, which is then assembled through the spinning process into an extremely strong fiber that requires very little energy.’
However, plant proteins such as SPI are poorly soluble in water, making it difficult to control their self-assembly into ordered structures.
The new technology therefore uses an environmentally friendly mixture of acetic acid and water combined with ultrasonication and high temperatures to improve the solubility of SPI.
This method produces protein structures with ‘intermolecular interactions’ guided by their unique and ultra-strong hydrogen bond formation.
In the second step the solvent is removed, resulting in the formation of a water-insoluble film.
The researchers used soy protein isolate (SPI) as their test plant protein, as it is readily available as a by-product of the soybean oil product.
The material has performance comparable to high performance engineering plastics such as low-density polyethylene – one of the most widely produced plastics in the world.
Polyethylene, also known as the #1 plastic, is used in everything from plastic bags, plastic milk jugs and shampoo bottles to…