Brush Your Transistors
Researchers showed that a common whitener found in toothpaste is ideal for making edible transistors, which could power medical devices.
If you have scanned the toothpaste aisle at your local supermarket recently, you have surely noticed one brand that claims to whiten teeth better than the others, or maybe another that boasts of its higher fluoride content. But can you imagine picking up a box of toothpaste that proudly advertises that it is packed with transistors? Truth be told, you probably never will. But technological progress can take some curious twists and turns from time to time, and thanks to a recent advancement, your toothpaste could be loaded with a heaping helping of transistors one day.
This seemingly very odd possibility arose after a group of researchers at the Istituto Italiano di Tecnologia and the University of Novi Sad took a close look at a common toothpaste additive called copper phthalocyanine. It is a blue pigment that, when applied to the teeth, acts as an optical filter that temporarily gives them a whiter appearance. As the day wears on it will work its way off of the teeth, and down the hatch it goes. As a result, we inadvertently consume about a milligram of copper phthalocyanine each time we brush our teeth — assuming this whitening agent is in our toothpaste, of course.
This provides us with some solid evidence that small amounts of copper phthalocyanine are safe for human consumption. Interestingly, the researchers realized that this pigment is good for more than just acting as a dye — it has properties that make it a good semiconductor, as well. So they used copper phthalocyanine in conjunction with other edible electronic components like ethylcellulose substrate, gold particles, and chitosan to build edible circuits containing transistors.
A single milligram of copper phthalocyanine is sufficient to produce about 10,000 transistors which may not sound like a lot by today’s standards. But it is well more than enough to, in theory, at least, build a processor on par with a 6502 or Z80 of yesteryear. And of course the transistors can be used in sensors and other components as well.
Stuffing these components into a tube of toothpaste may not make a lot of sense, but edible electronics most definitely have some important uses. Properly equipped, these devices could be swallowed to collect data from the gastrointestinal tract to aid doctors in diagnosing and treating a number of medical conditions. And when they are done with their job, they safely dissolve away into nothing.
To prove the concept, the team took the step of developing an edible electrolyte-gated organic field-effect transistor from a very small amount of copper phthalocyanine that is generally considered safe for human consumption. This transistor was demonstrated to be capable of greater than two orders of magnitude of current modulation. Furthermore, it is stable for over a year in the air, and can be driven by less than one volt.
Beyond healthcare, the researchers also envision their edible transistors being used in the food industry in the future. They might, for example, be able to serve as intelligent food tags.
