Tattoo ink with biosensorsPeople all over the world use tattoos to indicate many different things about themselves: personal interests, religious affiliations, family heritage, a deep and abiding love for guacamole, etc. Countless topics have adorned the human canvas, and now researchers at MIT and Harvard have developed tattoos that can also indicate what’s going on inside the body. The ink in these tattoos changes colors in response to different glucose, sodium or pH levels in the body, acting as automatic medical gauges on the skin. Researchers created the tattoo ink with biosensors that can measure the concentration of these chemicals in interstitial fluid (the liquid between our cells) and respond with different colors, which sure makes finger pricks seem outdated. While there are currently no plans to commercialize these medical-indicator tattoos, the technology could portend easier monitoring for diabetics, athletes and bio-curious tattoo lovers.