Health claims that “free radicals”—particles that are highly reactive because they have an unpaired electron—can damage human cells and possibly even cause cancer are pretty widespread. But by facilitating the buildup of static, these same malicious molecules wreak havoc on electronics too, scientists say.
This week, researchers from Northwestern University report in the journal Science that antioxidants such as vitamin E have the potential to combat free radicals—not just in the human body but also in polymers used for electronic equipment. The scientists showed that static electricity dissipates quickly if polymers are infused with vitamin E or other free radical “scavengers.”
Static electricity might seem harmless, but it can lead to a range of industrial accidents such as shocks and explosions. New research even points to static electricity as the cause of the 1937 Hindenburg airship disaster.
Today’s methods for dissipating static electricity focus on eliminating charges by ionizing the air or by applying chemical coatings that absorb water from the air to make a conductive surface. But these methods require special conditions, such as high humidity, and can take hours to eliminate static buildup.
“What if you remove not the charges per se but the helpers, the radicals?” asks Bartosz Grzybowski, a professor of physical chemistry at Northwestern, who led the research. “It’s so simple.”
Grzybowski and his team began testing theories of static electricity in 2009, when his lab bought a Kelvin probe force microscope with a grant from the U.S. Department of Energy. The microscope maps surfaces on an atomic or molecular scale by measuring the energy it takes to remove an electron from that surface. The team found that when a polymer is charged—such as when radiation breaks chemical bonds—the charges appear in positive and negative patches on the surface in a sort of heterogeneous, fractal structure. But in addition to these charged particles, the researchers reasoned, there should also be bonds breaking in another way, producing free radicals.
By upgrading their microscope, the team was able to look for free radicals, and they found them, as predicted, on the surface of various types of charged polymers. But surprisingly, the researchers also noticed that the radicals tended to stay near the patches of charge. “It could be coincidence, but I don’t believe in coincidences,” Grzybowski says. So the group investigated further and discovered that the radicals were stabilizing the charges by giving up or receiving electrons. The team realized then that if the radicals were playing a supporting role in the buildup of static electricity, they could also be the key to dispersing it.
The group treated, or “doped,” every polymer they could think of, from Scotch tape to resins like polystyrene, with vitamins and other radical scavengers, either by mixing them in liquid form or by soaking solid polymers in a mixture of organic solvent and the scavenger. They then imaged the polymer with the Kelvin probe force microscope as well as a magnetic force microscope, and they compared the data to readings of the same materials in untreated form. Their results showed that doped polymers discharged static electricity in minutes, while the untreated polymers took hours.
Takeo Suga, who studies charge-storage polymers at Waseda University, in Tokyo, says there is broad potential for applying the radical scavenger method to reduce static electricity in electronics. But there is a hitch: “Based on the radical scavenging mechanism, the radical additives are consumed by the repeated contact electrification,” he says. “A regenerative mechanism will be required for actual applications.”
But the potential applications in medical-device manufacturing, aerospace electronics, and other areas are numerous, says Grzybowski, and he doesn’t think the process will need very much development to be ready for industrial use. “It’s ready. I mean, you take a bucket of vitamin K and add it to a plastic, and if owing to that simple chemical your computer won’t fry, that’s great.”