More than 3,000 people a year swallow batteries in the US. Now a biomedical engineer has developed a way to reduce the resulting injuries and fatalities.
While choking is an obvious hazard when swallowing any small object, there’s also a serious risk from the current itself. When a battery is in a liquid such as saliva or stomach juices, it releases the current. The problem here isn’t electrocution, but rather that the current slowly breaks down surrounding liquids, increasing the proportion of the water made up of hydroxide ions.
Dr Jeff Karp is the senior author of a research paper on the subject published in the Proceedings of the National Academy of Sciences for the USA. He says the increase in hydroxide ions has the same effect as swallowing caustic soda. It can destroy tissue and even lead to uncontrollable bleeding when it damages major blood vessels.
Karp and his team spent two years working on a solution. They found it in quantum tunnelling composite, a silicone and metal compound that is used in some touchscreen designs. The way it works involves quantum mechanics, but the simplified version is that when the material is squeezed, the metal pieces get close enough to one another to produce a pathway for electrons. In its normal state, the material isn’t conductive.
Along with staff from MIT and Harvard, Karp developed a quantum tunnelling composite coating for batteries. The tests showed they still work as intended because the spring contacts that hold the battery in place inside a device create enough pressure to trigger the electron pathway. However, it doesn’t appear that swallowing would produce enough pressure, nor sustain any pressure for long enough, to release enough current to cause problems.
In testing the coating, the researchers found no problems when placing the batteries on gut tissue, inside live pig intestines, or soaking them for 24 hours in simulated stomach acid.
The team believe it would be possible to use the coating on existing batteries at a cost of a few cents, with no need to redesign electronic devices.