Jul 26 2016
Researchers from Penn State University have highlighted that at some point in the future chemically protective suits made from fabric coated in self-healing, thin films may be capable of preventing soldiers from biological or chemical attacks in the field, factory workers from accidental discharge of toxic materials and farmers from exposure to organophosphate pesticides.
SRT coated fabric self-heals. From left, fabric with hole, wet fabric and patch in a drop of water, self-healed fabric. (Photo Credit: Demirel Lab / Penn State)
Fashion designers use natural fibers made of proteins like wool or silk that are expensive and they are not self-healing. We were looking for a way to make fabrics self-healing using conventional textiles. So we came up with this coating technology.
Melik C. Demirel, Professor, Penn State University
The method involves an easy process of dipping the coating material in a series of liquids, and this leads to the development of material layers in order to form a self-healing, polyelectrolyte layer-by-layer coating.
This coating is deposited "under ambient conditions in safe solvents, such as water, at low cost using simple equipment amenable to scale-up," the researchers recently reported online in ACS Applied Materials & Interfaces.
Polyelectrolyte coatings are developed from both negatively and positively charged polymers, for instance, polymers like those in squid ring teeth proteins.
"We currently dip the whole garment to create the advanced material," said Demirel, who is also a member of the Huck Institutes of the Life Sciences. "But we could do the threads first, before manufacturing if we wanted to."
Enzymes can be included into the coating while layering. The researchers made use of urease - the enzyme that breaks urea into carbon dioxide and ammonia - however for market use, the coating would be adjusted with enzymes corresponding to the chemical being focused on.
If you need to use enzymes for biological or chemical effects, you can have an encapsulated enzyme with self-healing properties degrade the toxin before it reaches the skin.
Melik C. Demirel, Professor, Penn State University
The skin is capable of absorbing numerous toxic substances. For instance, organophosphates, that are used as insecticides and herbicides are absorbed through the skin and can have lethal effects. Some of these chemicals have additionally been employed as nerve agents.
Exposure can be minimized by a garment that is coated with a self-healing film comprising of an organophosphate hydrolase, which is an enzyme that is capable of breaking down the toxic material. In the presence of water, the squid ring teeth polymer is self-healing, so laundering would repair macro and micro defects in the coating, making the garments reusable and rewearable.
"The coatings are thin, less than a micron, so they wouldn't be noticed in everyday wear," said Demirel. "Even thin, they increase the overall strength of the material."
In order to build an environment where hazardous chemicals are required, clothing coated with an exact enzyme combination could secure against accidental chemical discharges. Further utilization of these coatings in medical meshes could also reduce infections in patients, enabling a fast recovery.
For the first time we are making self-healing textiles.
Melik C. Demirel, Professor, Penn State University
Some of the other Penn State researchers working on this project include Srinivas Tadigadapa, professor of electrical engineering and affiliate of the Materials Research Institute; David Gaddes, graduate student in bioengineering; and Huihun Jung and Abdon Pena-Francesch, graduate students in engineering science and mechanics.
Researchers from other universities include Genevieve Dion, assistant professor and director, Shima Seiki Haute Technology Lab, Drexel University; and Walter J. Dressick, U.S. Naval Research Laboratory, Washington, D.C. .
The work has been supported by the Army Research Office and the Office of Naval Research.