One less trip to Accident and Emergency (Day 185)

There's some good advice online about how to care for a child that is choking, but there are are other hidden dangers, especially from small button batteries.

It is fairly common for flat, round batteries that power toys, hearing aids, calculators, and many other devices to be swallowed.

Swallowing these batteries has severe consequences, including burns that permanently damage the oesophagus, tears in the digestive tract, and in some cases, even death.

However, there is some good news, which has grabbed headlines around the world and deserves a place in ChemEng365.

Researchers at MIT, Brigham and Women’s Hospital, and Massachusetts General Hospital have devised a new way to coat batteries with a special material that prevents them from conducting electricity after being swallowed.

In animal tests, they found that such batteries did not damage the gastrointestinal (GI) tract at all.

“We are all very pleased that our studies have shown that these new batteries we created have the potential to greatly improve safety due to accidental ingestion for the thousands of patients every year who inadvertently swallow electric components in toys or other entities,” says Robert Langer, the David H. Koch Institute Professor at MIT and a member of MIT’s Koch Institute for Integrative Cancer Research, Institute for Medical Engineering and Science (IMES), and Department of Chemical Engineering.

Billions of button batteries are produced every year, and these batteries have become more and more powerful, making them even more dangerous if 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.

Disc batteries in the oesophagus require emergency endoscopic removal. Tissue damage starts as soon as the battery is in contact with the tissue, generating an electric current and leading to a chemical burn.

The research team began thinking about ways to alter batteries so they would not generate a current inside the human body but would still be able to power a device. They knew that when batteries are inside their housing, they experience a gentle pressure.

To take advantage of this, they decided to coat the batteries with a material that would allow them to conduct when under pressure, but would act as an insulator when the batteries are not being compressed.

Quantum tunneling composite (QTC), an off-the-shelf material commonly used in computer keyboards and touch screens, fit the bill perfectly.

QTC is a rubberlike material, usually made of silicone, embedded with metal particles.

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. This allows QTC to switch from an insulator to a conductor, depending on how much pressure it is under.

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 movements of the tract, known as peristalsis, help move food along.

They calculated that even under the highest possible forces, found in patients with a rare disorder called “nutcracker oesophagus,” 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.

The coating is also waterproof and the researchers believe it could be used to make batteries weather-resistant and more suitable for outdoor use. They also plan to test the coating on other types of batteries, including lithium batteries.

IChemE Award Global winner in 2014, Paul Shearing from UCL, who is a battery expert, and was asked to comment on the innovation by BBC News, said the design was an "exciting possibility", as long as it could be widely applied.

As ever, these projects are multi-disciplinary, but it is great to see chemical engineers heavily involved in making everyday life safer for children, and potentially relieving the pressure on A&E teams.