What happened?

Tattoo-like medical sensors are being developed as low-cost and practical alternatives to more cumbersome blood tests, wearables or implantable devices. These sensors, which are either applied to our skin like a temporary tattoo or injected beneath the skin like a real tattoo, can deliver real time and continuous measurements of, for instance, electrolytes and metabolites in sweat, plasma, saliva or tear fluid. Such sensors are already used by diabetes patients to monitor their glucose levels and the future may see many more applications, even including markers related to (types of) cancer.

What does this mean?

The patch-like sensors are highly flexible, stretchable sensors and can last for weeks, virtually unnoticed. They provide rich data on a range of parameters. Most use electrochemical techniques to measure a physiological parameter and connect to a separate device to store and display results. Others are able to measure minute movements and can be used as elaborate activity trackers (e.g. in rehabilitation processes) and can also be used to generate power for other sensors (i.e. energy harvesting). In another class of sensors, experiments are also ongoing with ink-like material, such as engineered human cellsthat change color in response to specific molecules. These are thus actual tattoos that produce directly visible “measurements” on the surface of human skin.

What’s next?

These temporary tattoos and sub-skin injections augment our skin with an additional interface. While our skin can already display embarrassment or nerves (blushing) and other emotions such as fear (goose bumps) as well as more serious conditions (so-called flushing), these applications create new possibilities to quantify ourselves. Obviously, most applications will be strictly medical and applied only to those with a direct medical need, but on a more speculative note, we can imagine how these kinds of tattoos could end up becoming interactive body decorations or even be put to more malign use as, for example, publicly visible lie detectors or alcohol testers.