It can be a herculean task to get kids to eat their vegetables, but they'll happily chow down on things they aren't supposed to. If one of those things is a button battery, serious injuries can result in the form of burns to the esophagus or tears in the digestive tract. Researchers may not have found a way to stop kids swallowing button batteries, but they have found a way to make such culinary no-nos safer.
When a battery is swallowed, it has the potential to interact with water or saliva to create an electrical current. This can trigger a chemical reaction that produces hydroxide, a caustic ion that can cause serious burns if the battery isn't removed within a couple of hours. To prevent this, researchers at MIT, Brigham and Women's Hospital, and Massachusetts General Hospital have developed a coating that prevents the battery from conducting electricity.
The team's solution is built around the fact that batteries are subjected to a gentle pressure when inside their housing. This allowed them to create a coating from an off-the-shelf material commonly used in computer keyboards and touchscreens known as quantum tunneling composite (QTC), which can switch from an insulator to a conductor when pressure is applied.
This capability comes from the structure of QTC, which is a rubber-like material, usually made of silicon, that is embedded with metal particles. When not under any pressure, the metal particles are too far apart to conduct an electric current, but when compressed, the particles are pushed closer together allowing an electric current to flow.
To ensure the coating would remain an insulator inside the body, the team first calculated how much pressure would be exerted on the battery inside the digestive tract, where peristalsis causes muscles to contract and relax in a wave to propel food through.
They calculated that even when subjected to the highest possible forces found in those with a rare disorder called "nutcracker esophagus," the QTC-coated batteries would remain non-conductive. After completing these calculations, the researchers tested the coated batteries in the esophagus of a pig and saw no signs of damage.
The researchers believe that because QTC is relatively inexpensive and already used in various other consumer products, it would be a fairly simple task for battery companies to implement the technology. To this end, they are now working on a scalable method for the manufacture of coated batteries and seeking interest from manufacturers.
"We were really interested in trying to impose design criteria that would allow us to have an accelerated path to get this out into society and reduce injuries," says Jeffrey Karp, an associate professor of medicine at Harvard Medical School and Brigham and Women’s Hospital. "We think this is a relatively simple solution that should be easy to scale, won’t add significant cost, and can address one of the biggest problems associated with ingestion of these batteries."
Aside from improving battery safety, the researchers say the coating could also make batteries weather-resistant and more suitable for outdoor use as it is waterproof. They also plan to test the coating on other battery types, including lithium-ion batteries.
A paper describing the team's battery coating was published this week in the Proceedings of the National Academy of Sciences.