The days of plastic derived from oil may be coming to an end, thanks to work by an international team including Penn State researchers.
The team, which includes Melik Demirel, professor of engineering science and mechanics at Penn State, is investigating biological plastics, or elastomeric materials, that can be grown and have the same characteristics as conventional plastics.
Biological polymers are everywhere, Demirel said, but until recently, scientists couldn’t find the right molecular structure in nature that had the same properties as regular plastic.
For example, biological polymers exist in a person’s hair and fingernails, but they make for a poor plastic.
“The issue with your hair or nails is that you can heat them up, but you can’t mold them,” he explained. “What you need is a material that is soft, but moldable.”
It wasn’t until a collaboration with researchers at Nanyang Technological University in Singapore that Demirel and his colleagues discovered that the elastomeric structures in squid proteins could be used to produce elastomeric polymers.
“This was the Holy Grail,” Demirel stated. “It doesn’t exist in any other known species.”
The team’s work centers on various types of squid from around the world.
“We have to collect live squid to extract the genomic information.”
By understanding the genomes behind the squids’ elastomeric structures, the researchers can grow their own natural plastic.
Demirel said his work began with investigating biological asymmetric structures, trying to understand how nature solves problems, such as butterfly wings’ ability to shed water and gecko feet’s capacity for scaling walls.
The idea, Demirel said, was to mimic these natural structures to create tools on the micro- and nano scales.
“The issue became whether we could make these devices or not.”
But the strategy to imitate animals’ abilities proved extremely challenging and costly.
Then the team struck upon the idea of using the genomic blueprint nature already was providing.
While his colleagues in Singapore had an excellent grasp of the squid’s genomic information, it wasn’t until the addition of Demirel’s materials expertise that everyone realize the squid was animal the team was looking for.
“We found that it could be molded and reshaped,” Demirel said of the squid’s elastomeric structure.
The result was a next generation soft material that can transform from a complete solid to liquid.
“It can go from colloidal gas to liquid to solid,” he said.
The materials can be shaped into almost anything that consumer plastics are made of. Demirel said elastomerics could be used in medical implants, for example, or gels in tissue scaffolds.
But it could prove to be a game-changer in consumer products.
“The big impact will come in an eco-friendly area. This will open up the door,” he said.
Demirel said the work has gone beyond the laboratory stage.
“The key issue was, ‘How can we make this cheaper and in a large scale?’ Now we have the technology and we have the information to produce these materials.”
He said according to the U.S. Environmental Protection Agency, in 2010 the country generated nearly 14 million tons of oil-based plastics for use as containers and packaging, about 11 million tons for durable goods such as appliances and 7 million tons for non-durable goods such as plates and cup. Of the plastic generated, only 8 percent was recovered for recycling.
The engineer said the team’s elastomeric material is infinitely recyclable and can be easily turned from solid to liquid to solid again.
“elastomeric material lasts a long time. It is a plastic, but it’s bio-derived,” Demirel said. Unlike conventional plastic, “it’s a protein. It’s a part of nature.”
Curtis Chan is the coordinator of College Relations at Penn State College of Engineering.