Energy Focus: Skin pigment enables edible battery for biodegradable devices
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Energy Focus Skin pigment enables edible battery for biodegradable devices
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y using the skin pigment melanin as an electrode material, researchers have made batteries that people could swallow. Such edible batteries could potentially power medical implants that disintegrate in the body instead of having to be surgically removed. The idea behind biodegradable electronics is to make devices that go into the body, for example, to measure temperature, monitor wounds, or deliver drugs. Once their job is done, the devices could crumble into smaller pieces that are easily eliminated by the gastrointestinal tract, said Christopher Bettinger, a materials science and engineering professor at Carnegie Mellon University (CMU). “Unlike a pacemaker that has to last for five years, such edible electronics only need to last about 20 hours,” he said. “So we want simple devices that are cheap and biocompatible.”
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VOLUME 39 • MARCH 2014
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lease kinetics. The device’s function is not materials-dependent, Kohane said. “Unlike other approaches where the drug was distributed throughout the lens, in our design there was a real advantage from its macroscopic nature. The larger an object is, the smaller its surface area to volume ratio and therefore the slower and more controlled its release is going to be. The key concept here is the design rather than the specific materials.” While one concern for commercialization of the contact lens is degradation during storage, the PLGA can in principle be switched with a polymer with a longer shelf life. Nor is the lens substrate materialscritical. In the long term the team may switch to contemporary silicone hydrogel lenses. For now they will try to increase the size of the film “window.” Currently the aperture is equivalent to that of eye-color-changing contact lenses, but the researchers want the light transmission to be close to that of vision-correcting lenses.
“Here you have a contact lens that could be built with the patient’s refractive correction, so that the patient would be seeing better using the lens.... Right now patients don’t have much incentive to be compliant with their glaucoma medications. Glaucoma is commonly asymptomatic so most patients don’t appreciate any vision loss until it’s too late. So I think something that adds an incentive that is currently not there would be beneficial to improving compliance,” said Ciolino. Anuj Chauhan of the University of Florida uses vitamin E to slow contact lens drug release. “The strength of [the Boston] work is that you can release the medication for a month at zero-order release rates. Vitamin E is not zero order, it’s diffusion-controlled. The advantage of the thin films is that you get close to zero-order release. Other methods have their own advantages, and it’s good that multiple people are working on the problem.” Jen Gordon
Bettinger and others have already made biodegradable transistors and capacitors using various natural and synthetic materials. But the essential power sources for edible electronics were
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