Sep 4 2015
An international collaboration of researchers has discovered that a drop of water could self-heal a multiphase polymer developed based on the genetic code of squid ring teeth. This breakthrough research holds promise for extending the service life of fiber-optic cables, medical implants and other difficult to repair in place objects.
"What's unique about this plastic is the ability to stick itself back together with a drop of water," said Melik Demirel. Image: Demirel Lab/Penn State
"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, Penn State. "There are other materials that are self healing, but not with water."
The team observed the ring teeth of squids procured from various parts of the world including the Atlantic, Mediterranean, Argentina, near Hawaii and the Sea of Japan. They realized that all the samples possessed proteins with self-healing characteristics. However, in a recent issue of Scientific Reports, they explained that "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."
Demirel’s team chose the field of biotechnology to create the proteins in bacteria, so as to create a uniform material, and not deplete squid populations. By using heat or by casting using solvent evaporation, the polymer can be molded.
The material is a copolymer possessing two parts - an unstructured segment that is soft, and a well structured molecular architecture.
The structured part is made up of strands of amino acids linked by hydrogen bonds to form a pleated and/or twisted sheet. This part provides the polymer with strength. The unstructured part is what provides the polymer with the self-healing ability.
self-healing polymer
The research team built a polymer sample in the shape of a dog-bone and then split it into two. When a combination of minimal pressure with a metal tool and warm water at approximately 113°F was applied on the two portions, they reunited to once again form the dog-bone shape. Strength tests performed on the material revealed that after healing, the material was as strong as when first produced.
"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 said. "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."
Abdon Pena-Francesch and Huihun Jung, graduate students in engineering science and mechanics; and Carlos Pacheco, NMR spectroscopist were also involved in this project at Penn State.
Others include Metin Sitti, Max Planck Institute at Stuttgart, Germany and Carnegie Mellon University; Veikko Sariola, former postdoctoral fellow at Carnegie Mellon University; and Murat Cetinkaya, BASF SE, Ludwigshafen, Germany. Sariola and Pena-Francesch were co-first authors of this paper.
The Jenny and Antti Wihuri Foundation, Walter Ahlström Foundation, Academy of Finland, the National Science Foundation and the Office of Naval Research supported this work.