A screenshot from a video explaining how the biosensitive ink works. Photo: Harvard Medical School

In a proof-of-concept project, researchers from Harvard and MIT showed that “smart” tattoo ink can monitor an individual’s health by changing colors to indicate dehydration in athletes, or high blood sugar levels in diabetics, for example.

The study included a collaboration between MIT researchers Katia Vega, Xin Liu, Viirj Kan and Nick Barry, and Harvard Medical researchers Ali Yetisen and Nan Jiang.

The biosensitive ink project, referred to as Dermal Abyss, demonstrates how the body’s surface could potentially act as an interactive display to better monitor health conditions.

Traditional ink was replaced with color-changing biosensors: The pH sensor changed between purple and pink, and the glucose sensor between blue and brown, according to the researchers. A sodium and second pH sensor fluoresced at a higher intensity under UV light.

The change in color is a response to the chemistry of the body’s interstitial fluid. For example, with the glucose sensor, the ink changes from green to brown as glucose concentration increases.

The team tested the effectiveness of the ink using segments of pig skin and observed how the ink changed color or intensity in response to different biomarkers. The glucose ink is of particular interest, as it could eliminate diabetes patients from having to conduct blood draws from finger pricks multiple times daily to measure their glucose levels

The ink does solve some of the limitations with current biomedical monitoring devices – there would be no need to worry about battery life, or the need for wireless connectivity. But there are other challenges presented with this method – like ensuring the ink won’t fade over time or diffuse into surrounding tissue.

Lio and Vega did reiterate that the Dermal Abyss project is strictly a research project, and there are currently no plans to develop the biosensor ink into a medical product, or progress with clinical trials. The goal of the work was to spark innovative ideas and highlight the potential of this type of technology.

But the researchers did note that the ink could potentially be useful in a wide variety of applications – from monitoring chronic conditions, to creating temporary designs for shorter-duration monitoring. The ink could also help astronauts continuously monitor their health as part of space exploration missions.

The ink could also be developed to only be visible under specific kinds of light, such as from a smartphone, to address possible privacy concerns.