Biosensitive tattoos monitor glucose, hydration levels

Researchers at Harvard and MIT have developed smart tattoo ink that changes colour if the wearer is dehydrated or if his/her blood sugar rises.

HMS postdoctoral fellows Ali Yetisen and Nan Jiang collaborated with MIT researchers to develop the biosensitive tattoo ink, which, unlike current wearable monitoring devices, doesn’t require batteries or wireless connectivity.

The project, ‘Dermal Abyss’, was conducted as a proof of concept, and further refinements — stabilising ink so designs don’t fade or diffuse into surrounding tissue — would be required for a medical product.

The Dermal Abyss tattoo inks change colour according to the chemistry of the body’s interstitial fluid, which can be used as a surrogate for constituents of the blood. Inks developed so far change from green to brown as glucose concentration increases.

The team also developed a green ink, viewable under blue light, that grows more intense as sodium concentration rises, an indication of dehydration. Researchers tattooed the inks onto segments of pig skin and noted how they changed colour or intensity in response to different biomarkers.

Jiang and Yetisen said that once the bugs are worked out, the applications for biologically sensitive ink are fairly broad. Inks, Yetisen said, could be incorporated into long-lasting tattoos for chronic conditions or into temporary designs for shorter-duration monitoring. Ink can even be invisible, Yetisen said, readable under only particular kinds of light. That light could come from something as ubiquitous as a smartphone.

Yetisen has already developed an app that can analyse a picture of a sensor and provide quantitative diagnostic results. While patients are an obvious potential market, Yetisen said the technology could be used in astronauts, for whom continuous health monitoring is desirable.

Jiang said the project’s purpose was to excite artists and scientists alike about the potential for such technology, and to stimulate discussion of ethical issues it might raise, such as people’s willingness to have health information displayed for all to see.

A drawback of current wearable monitoring devices is that they don’t seamlessly integrate with the body, Yetisen said. Short battery life is a concern and so is the need for wireless connectivity, neither of which is an issue with the simple, colour-based interface of biosensitive tattoo ink.