Protection from Chemical Agents

Thursday, January 31, 2013 @ 05:01 PM gHale

There may soon be a process out there that not only benefits every uniformed service member, but everyone else as well: Protection from Chemical/Biological agents.

Not only will this new discovery help ward off chemical and biological agents, it could also lead to self-cleaning apparel, to effortless thermal management, to fuel purification as well as enhanced control of leaks, especially with oil and fuels.

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A research team led by Anish Tuteja, University of Michigan in Ann Arbor assistant professor of materials science and engineering, specializing in chemical engineering and macromolecular science and engineering, demonstrated surfaces can effectively perform as “chemical shields against virtually all liquids.”

In 2006, Air Force Office of Scientific Research (AFOSR) Program Manager Dr. Charles Lee funded Professor Gareth McKinley at the Massachusetts Institute of Technology exploring nanocomposite technology for Defense applications. Tuteja, an MIT doctoral student at the time, was exploiting the unusual surface properties of a nanocomposite with fluorinated nanoparticles, to create a superoleophobic surface. After graduation, Tuteja moved to the University of Michigan. He earned the Young Investigator Program grant from AFOSR in 2011, and continued to conduct the same line of research begun at MIT.

To create chemical shields against liquids, surfaces undergo preparation using a nanoscale coating approximately 95 percent air, which in turn, repels liquids of any material in its class, causing them to literally bounce off the treated surface. The surfaces “possess hierarchical scales of re-entrant texture that significantly reduce the solid-liquid contact area,” Tuteja said. It all comes down to controlling how much contact the liquid ultimately has with the treated surface. To accomplish that the researchers apply the nanoscale coating using a process called electrospinning, using an electric charge to create fine particles of solid derived from a liquid solution.

The coating is a mixture of cross-linked “polydimethylsiloxane,” or PDMS, and liquid-resisting nanoscale cubes developed by the Air Force that contain carbon, fluorine, silicon and oxygen. While the material’s chemistry is important, so is its texture, because it hugs the pore structure of whatever surface it is applied to, and creates a fine web of air pockets within those pores, so any liquid that comes in contact with the coating is barely touching a solid surface.

Tuteja said when an untreated surface and a liquid get in close proximity, “they imbue a small positive or negative charge on each other, and as soon as the liquid comes in contact with the solid surface, it will start to spread….we’ve drastically reduced the interaction between the surface and the droplet.” By effectively eliminating the contact between the treated surface and the liquid, there is almost no incentive for the liquid to spread, as such, the droplets stay intact, interacting only with molecules of themselves, and maintaining their spherical shape.

The research team has tested more than 100 liquids and found only two that were able to penetrate the coating: They were both chlorofluorocarbons—chemicals used in refrigerators and air conditioners. In Tuteja’s lab demonstrations the surface repelled coffee, soy sauce and vegetable oil, as well as toxic hydrochloric and sulfuric acids, and the surfaces are also resistant to gasoline and various alcohols.

This program is can be useful to the Air Force and the Department of Defense for self-cleaning surfaces (in particular, integral breathable protective Chemical/Biological Warfare defense in uniform clothing and sensor systems), improvement of thermal management efficiency in phase change cooling systems, fuel purification and the control of oil and fuel leakages in rockets and airplanes.

Don’t forget, it can also protect against dreaded everyday coffee spill.



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