Coating prevents electrical current from damaging the digestive tract after battery ingestion.
Every year, nearly 4,000 children go to emergency rooms after swallowing button batteries — the flat, round batteries that power toys, hearing aids, calculators, and many other devices. Ingesting these batteries has severe consequences, including burns that permanently damage the esophagus, tears in the digestive tract, and in some cases, even death.
To help prevent such injuries, 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.
Langer and Jeffrey Karp, an associate professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, are the senior authors of a paper describing the new battery coatings in this week’s edition of the Proceedings of the National Academy of Sciences. The paper’s lead authors are Bryan Laulicht, a former IMES postdoc, and Giovanni Traverso, a research fellow at the Koch Institute and a gastroenterologist at MGH.
About 5 billion button batteries are produced every year, and these batteries have become more and more powerful, making them even more dangerous if swallowed. In the United States, recent legislation has mandated warning labels on packages, and some toys are required to have battery housings that can only be opened with a screwdriver. However, there have been no technological innovations to make the batteries themselves safer, Karp says.
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 esophagus require [emergency] endoscopic removal,” Traverso says. “This represents a gastrointestinal emergency, given that 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 esophagus,” the QTC-coated batteries would not conduct.
“You want to know what’s the maximum force that could possibly be applied, and you want to make sure the batteries will conduct only above that threshold,” Laulicht says. “We felt that once we were well above those levels, these coatings would pass through the GI tract unchanged.”
After those calculations were done, the researchers monitored the coated batteries in the esophagus of a pig, and found no signs of damage.
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.
“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,” Karp says. “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.”
Also, because the coating is waterproof, 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.
Edith Mathiowitz, a professor of medical science at Brown University who was not involved in the research, says she believes this approach is a “brilliant idea” that offers an easy fix for the potential dangers of battery ingestion.
“What I like about it is that it’s a simple idea you could implement very easily. It’s not something that requires a big new manufacturing facility,” she says. “And, it could be useful eventually in any type of size of battery.”
Simple Explanation of What how a Battery Works
So, how do batteries work
Electricity, as you probably already know, is the flow of electrons through a conductive path like a wire. This path is called a circuit.
Batteries have three parts, an anode (-), a cathode (+), and the electrolyte. The cathode and anode (the positive and negative sides at either end of a traditional battery) are hooked up to an electrical circuit.
The chemical reactions in the battery causes a build up of electrons at the anode. This results in an electrical difference between the anode and the cathode. You can think of this difference as an unstable build-up of the electrons. The electrons wants to rearrange themselves to get rid of this difference. But they do this in a certain way. Electrons repel each other and try to go to a place with fewer electrons.
In a battery, the only place to go is to the cathode. But, the electrolyte keeps the electrons from going straight from the anode to the cathode within the battery. When the circuit is closed (a wire connects the cathode and the anode) the electrons will be able to get to the cathode. In the picture above, the electrons go through the wire, lighting the light bulb along the way. This is one way of describing how electrical potential causes electrons to flow through the circuit.
However, these electrochemical processes change the chemicals in anode and cathode to make them stop supplying electrons. So there is a limited amount of power available in a battery.
When you recharge a battery, you change the direction of the flow of electrons using another power source, such as solar panels. The electrochemical processes happen in reverse, and the anode and cathode are restored to their original state and can again provide full power.
What are Batteries
A battery can change chemical energy to electricity by putting certain chemicals in contact with each other in a specific way. Electrons, which are small parts of an atoms, will travel from one kind of chemical to another under the right circumstances. When electrons flow, this makes an electrical current that can power something. What a battery does is put the right chemicals in the right relationships, and then puts a wall between them. Only when the two sides of a battery are connected by a wire or another conductor can the electrons flow.
Batteries come in several styles; you are probably most familiar with single-use alkaline batteries. NASA spacecraft usually use rechargeable nickel-cadmium or nickel-hydride batteries like those found in laptop computers or cellular phones. (DS1 uses nickel-hydrogen batteries.) Engineers think of batteries as a place to store electricity in a chemical form.
Batteries tend to expend their charge fairly quickly. DS1 can last from half an hour to three hours running purely on battery power before the batteries need to be recharged from the solar panels. These batteries are recharged thousands of times over the life of the spacecraft.
– Credit and Resource –
Anne Trafton | MIT News Office