Many parents have felt panic after seeing their toddler furtively sneak an unknown object in their mouth. The small batteries found in remote controls, laser pointers and toys are an example of just how dangerous that roulette can be.

In 2013, the National Capital Poison Center reported over 3,000 cases of ingested batteries, with over 2,000 of those occurring in children less than 6 years old. While the majority of batteries don't cause serious damage, the button-sized nubs can get stuck in the esophagus, leaving tissue burns, tearing the lining and even causing death.

The larger buttons, at 20 millimeters in diameter, are particularly dangerous. "One out of 8 children [under 6 years old] who swallow this larger battery are going to have a serious debilitating complication," says Dr. Tovy Litobitz, executive director of the National Capital Poison Center, which runs the National Battery Ingestion Hotline. The batteries can cause injuries that require surgical repair or the use of a tube for feeding or breathing.

Now, researchers from the Massachusetts Institute of Technology, Harvard Medical School and the Harvard Stem Cell Institute have created a shield that pastes directly onto the the negative terminal of the battery.

The results of their experiments published Monday in the Proceedings of the National Academy of Sciences show that a prototype shield is effective at keeping small, 11 millimeter batteries from damaging the esophagus after being swallowed.

Microscopic metal particles are embedded in the shield, which is a millimeter thick. When a battery is inserted into a device, the pressure from the device's cover or a spring that holds the battery in place pushes the metal particles together. The shield then acts like a switch, conducting electricity.

When the battery is free, floating down a child's esophagus, for instance, there's not enough pressure to make the microparticles smush together. The shield then acts as an insulator.

To test the prototype battery, the researchers put it and a regular button battery in two pig esophagi for two hours. They also inserted a camera to look for damage. While the normal battery damaged the lining of the esophagus, the shielded battery left no trace.

They also put three shielded batteries into a laser pointer and found that the pointer worked normally.

The shield's material is commercially available and currently used in touch-screen devices where a gentle press of a fingertip can complete a circuit.

The researchers say the material's availability makes it a cheap solution. "We think that probably it's going to be in the range of pennies per battery," Jeffrey Karp, associate professor at Harvard Medical School and an author of the study tells Shots.

The next step, he says, is to test the prototype battery in a wider range of devices to make sure it functions and fits like a traditional button battery.

Karp says considering battery safety hasn't significantly improved since batteries were created, this approach is surprisingly inventive, "It's a very simple, off-the-shelf potential solution."

However, it's too early to say if battery companies will be interested in buying the shield, and there are still many unanswered questions, says Litobitz. How long will the protective coating last in the body? Will it work with the bigger button batteries too? Will the coating deter companies that want the slimmest possible batteries to fit inside their toys?

"There are a lot more issues here that have to be investigated," she says, adding, "it would be a game-changer if it worked."

Copyright 2021 NPR. To see more, visit https://www.npr.org.