Melik said the synthesis is classical protein expression, whereby the target squid protein is expressed in bacteria through a fermentation process. He added that the researchers are currently using E. coli, but are trying to express the protein in yeast, which has the advantage of secreting the protein, thus eliminating a purification step and reducing cost. Melik described the resulting polymer as a thermoplastic elastomer with both soft and brittle components whose self-healing mechanism is governed by hydrogen bonding and offering claimed "tunability in physical performance." He said the polymer is amenable to standard plastic processes like extrusion, injection molding, and blow molding, as well as coating techniques like casting, spin coating, and dip coating; typical coating thickness ranges from 10 nm to several millimeters depending on the application.
The group is currently using Penn State facilities; specifically it is employing a 300 L fermenter which produces 100 g of target polymer in 24 hrs. Melik said current cost using E. coli bacteria is $250/kg to $300/kg, but he aims to reduce cost below $50/kg to by moving to yeast. Target applications include cosmetics, DNA swabs, medical meshes and sutures, food packaging, 3D printing, textiles, and water purification. Melik said he is currently in talks with a cosmetics company and a medical company.
Melik's team is wise to focus on improving process economics as current cost will be quite commercially prohibitive. Although even below $50/kg, the self-healing polymer is likely to price out all but the most high performance applications, which likely explains the initial traction with companies from the high-margin cosmetics and medical industries. What's more, Penn State's material will also have to compete with other self-healing innovations being developed by the likes of NEI Corporation, PPG, LG Electronics, Autonomic Materials, GK Materials, Nanosonic, Luna Innovations, and IBM. That being said, the bio-based nature of Penn State's self-healing polymer is distinct and offers potentially significant life cycle advantages. Overall, this is a compelling bio-based performance technology to watch.
Ross Kozarsky is a Research Director who leads the materials teams at Lux Research, which provides strategic advice and on-going intelligence for emerging technologies. For more information, visit Lux Research.