A single drop of water is all that is needed to repair tears in a novel multiphase polymer derived from the genetic code of the suckers on squid tentacles, known as ring teeth. This polymer could help extend the life of medical implants, fiber-optic cables and other objects in hard to reach places, according to an international team of researchers.
"What's unique about this plastic is the ability to stick itself back together with a drop of water," said Melik Demirel, professor of engineering science and mechanics at Penn State. "There are other materials that are self healing, but not with water."
"What's unique about this plastic is the ability to stick itself back together with a drop of water. There are other materials that are self healing, but not with water."Melik Demirel, Penn State.
Demirel and his team looked at the ring teeth of squid collected from around the world -- in the Mediterranean, Atlantic, near Hawaii, Argentina and the Sea of Japan -- and found that they all contain proteins with self-healing properties. However, as the researchers note in a recent issue of Scientific Reports, "the yield of this proteinaceous material from natural sources is low (about 1 gram of squid ring teeth protein from 5 kilograms of squid) and the composition of native material varies between squid species."
So as not to deplete squid populations, and to produce a uniform material, the researchers used biotechnology to create genetically-modified bacteria that could synthesize the proteins. They then used these proteins to produce a polymer that can either be molded with heat or cast by solvent evaporation.
The two-part material is a copolymer consisting of an amorphous segment that is soft and a harder segment with a more structured molecular architecture. The structured portion consists of strands of amino acids connected by hydrogen bonds to form a twisted and/or pleated sheet. This part also provides strength for the polymer, but the amorphous segment provides the self-healing.
The researchers created a dog-bone shaped sample of the polymer and then cut it in half. Next, they brought the two halves together while exposing them to drops of warm water at about 113°F – slightly warmer than body temperature – and applying a small amount of pressure with a metal tool, causing the two halves to reunite. Strength tests showed that the material after healing was as strong as when originally created.
"If one of the fiber-optic cables under the ocean breaks, the only way to fix it is to replace it," said Demirel. "With this material, it would be possible to heal the cable and go on with operation, saving time and money.
"Maybe someday we could apply this approach to healing of wounds or other applications," he continued. "It would be interesting in the long run to see if we could promote wound healing this way, so that is where I'm going to focus now."
This story is adapted from material from Penn State, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.