This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.
In April, bombs fell on Khan Shaykhun, a village in the Middle Eastern country of Syria. The explosions released toxic chemicals that killed or injured hundreds of people. Some toxic materials kill when people breathe them in. Others need only pass through the skin to be deadly. On battlefields and in war-torn countries such as Syria, protection against attacks by skin exposure to chemical weapons is a life-or-death need. And a new technology may help them. It would put such protection in a person's clothing
Scientists recently showed how to coat fabric with a light layer of a certain chemical mix. This coating can absorb and neutralize chemical weapons in minutes. The U.S. military wants such a fabric for soldiers. Civilians in war-torn regions also might benefit from clothing treated with the new technology.
Engineers described their new coating June 13 in Chemistry of Materials.
The coating’s secret ingredient is a chemical known as a metal-organic framework, or MOF. Such materials are composed of carbon-containing molecules attached to clusters of metal atoms. These materials have tiny holes, or pores, that can trap other chemicals. An MOF can interact with the trapped chemicals to break them down into harmless pieces. In the last few years, scientists have identified many different MOFs.
“This light [MOF] material can absorb the nasty chemicals or harmful agents, and at the same time deactivate them,” explains Omar Farha. He is a chemist at Northwestern University in Evanston, Ill. Farha did not work on the fabric coating. But he knows all about it. His research focuses on materials that can hold chemicals and break them into less toxic substances. Those materials include MOFs. In the past, his lab identified MOFs that could be used to store and break down toxic chemicals on clothing. (The researchers didn't test these materials with chemical weapons. Instead, they used harmless chemicals with very similar structures.)
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An un-sticky problem
After Farha's team identified its candidate MOF, scientists looked for a way to use it as a chemical shield. That's where Greg Parsons and his team came in. He’s a chemical engineer at North Carolina State University, in Raleigh. He also does research for the U.S. Army, which asked him to help add Farha's MOF to fabrics.
This proved a major challenge. The MOF “doesn't want to stick to fibers that are typically used in clothing,” Parsons found. The material is like a powder made of tiny crystals. If you tried to sprinkle it on a piece of clothing, it would blow right off. (Imagine pouring sugar or salt crystals onto your shirt — they won't stay put!)
But Parsons had some ideas about how to solve that problem. He’s an expert in another area of science that requires getting materials to bond: electronics.
Many computer chips use a crystal made of silicon coated with thin layers of materials called metal oxides. To get metal oxide onto a chip surface, engineers use a process called atomic layer deposition. They expose the surface of a device to tiny quantities of chemical vapors, or gases. Those gases react with the surface. This chemical reaction leaves behind tiny amounts of a metal oxide. Over time, the process totally coats the surface with a very thin metal-oxide layer.
Parsons and his team used the same concept to solve their un-sticky problem. They first used atomic layer deposition to build up a thin layer of metal oxide on a fabric. That metal oxide let the MOF adhere tightly to the fabric.
Then they tested the treated fabric. They exposed it to a chemical similar to sarin. Sarin is a colorless, deadly poison that may be liquid, powder or gas. Experts believe Syrians were exposed to sarin gas during April's attacks. A person can sicken or die by breathing or touching sarin. Treated clothing would keep sarin off someone’s skin.
Previous materials have been able to capture toxic chemicals. They did not, however, degrade them quickly. In lab tests, the new material broke down the sarin-like chemical in as little as five minutes. “The faster the better,” says Farha.
Parsons says the treated clothing worked in the lab, but it's not ready for the real world just yet. He and his colleagues are still trying to find exactly the right MOF recipe to treat clothing. They also want to be able to treat lots of fabric at once. “Right now it's a very slow and tedious process,” he says. “We're thinking about how can we can do this quicker with the same good outcome.”
agent A compound or activating form of energy (such as light or other types of radiation) that has a role to play in getting something done.
atom The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
atomic Having to do with atoms, the smallest possible unit that makes up a chemical element.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
chemical engineer A researcher who uses chemistry to solve problems related to the production of food, fuel, medicines and many other products.
chemical reaction A process that involves the rearrangement of the molecules or structure of a substance, as opposed to a change in physical form (as from a solid to a gas).
chemistry The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances.
colleague Someone who works with another; a co-worker or team member.
compound (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.
computer chip (also integrated circuit) The computer component that processes and stores information.
crystal (adj. crystalline) A solid consisting of a symmetrical, ordered, three-dimensional arrangement of atoms or molecules. It’s the organized structure taken by most minerals. Apatite, for example, forms six-sided crystals. The mineral crystals that make up rock are usually too small to be seen with the unaided eye.
deposition (in chemistry) When atoms settle or are deposited onto a separate material (which is generally known as a substrate).
electronics Devices that are powered by electricity but whose properties are controlled by the semiconductors or other circuitry that channel or gate the movement of electric charges.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
fabric Any flexible material that is woven, knitted or can be fused into a sheet by heat.
fiber Something whose shape resembles a thread or filament. (in nutrition) Components of many fibrous plant-based foods. These so-called non-digestible fibers tend to come from cellulose, lignin, and pectin — all plant constituents that resist breakdown by the body’s digestive enzymes.
liquid A material that flows freely but keeps a constant volume, like water or oil.
metal organic framework (or MOF) These carbon-based chemicals contain clusters of metal atoms that can trap — and chemically react with — other compounds.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
organic (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms.
oxide A compound made by combining one or more elements with oxygen. Rust is an oxide; so is water.
pore A tiny hole in a surface. On the skin, substances such as oil, water and sweat pass through these openings.
salt A compound made by combining an acid with a base (in a reaction that also creates water). The ocean contains many different salts — collectively called “sea salt.” Common table salt is a made of sodium and chlorine.
sarin A chemical warfare agent that is usually dispersed as a gas. Known as a nerve agent, it has no color, smell or taste. German scientists developed sarin in the 1930s as an insect-killing chemical. It works by lethally deactivating the enzyme system that would turn off an already stimulated muscle or gland. Even one drop on the skin can cause sweating and muscle twitching. Larger doses can cause paralysis, convulsions, unconsciousness and death.
silicon A nonmetal, semiconducting element used in making electronic circuits. Pure silicon exists in a shiny, dark-gray crystalline form and as a shapeless powder.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
vapors Fumes released when a liquid transforms to a gas, usually as a result of heating.
Journal: D.T. Brown et al. Catalytic “MOF-Cloth” formed via directed supramolecular assembly of UiO-66-NH2 crystals on atomic layer deposition-coated textiles for rapid degradation of chemical warfare agent simulants. Chemistry of Materials. Vol. 29, June 13, 2017, p. 4894. doi: 10.1021/acs.chemmater.7b00949.
Web page: Facts about sarin, by U.S. Centers for Disease Control and Prevention.