Each year, nearly 4,000 children go to emergency rooms after swallowing button batteries, which can cause burns that damage the esophagus, tears in the digestive tract, and in some cases, even death. To help prevent such injuries, researchers at MIT, Cambridge, MA, Brigham and Women's Hospital, and Massachusetts General Hospital, Boston, MA, have devised a new way to coat batteries with a special material that prevents them from conducting electricity after being swallowed.

When batteries are swallowed, they start interacting with water or saliva, creating an electric current that produces hydroxide, a caustic ion that damages tissue. This can cause serious injury within just a couple of hours, especially if parents don't realize right away that a child has swallowed a battery.

The researchers decided to coat the batteries with a material that would allow them to conduct electricity when under pressure, but would act as an insulator when the batteries are not being compressed. Quantum tunneling composite, an off-the-shelf material commonly used in computer keyboards and touch screens, is a rubberlike material, usually made of silicone, embedded with metal particles, provided the answer they were seeking. Under normal circumstances, these particles are too far apart to conduct an electric current. However, when squeezed, the particles come closer together and start conducting.

To verify that this coating would protect against tissue damage, the researchers first calculated how much pressure the battery would experience inside the digestive tract, where peristalsis helps move food along. They calculated that even under the highest possible forces, the QTC-coated batteries would not conduct.

Because QTC is relatively inexpensive and already used in other consumer products, the researchers believe battery companies could implement this type of coating fairly easily. They are now working on developing a scalable method for manufacturing coated batteries and seeking companies that would be interesting in adopting them.