“This is a real-time, wireless response from a sensor that can be directly interfaced with a variety of biomaterials,” said Michael McAlpine, the team’s principal investigator. He said the system not only has the ability to supply fast results, but is able to detect very small amounts of bacteria — a feature that could prove critical in treating certain diseases.

The researchers created the tattoo by bundling the silk and gold with graphene — an extremely thin sheet of carbon in which atoms are arranged in a honeycomb lattice. The material’s unique properties allowed the researchers to construct a small, flexible device able to detect bacteria at a much higher sensitivity level than traditional methods. In tests, the researchers detected samples of bacteria that can cause surgical infections and others that can lead to stomach ulcers.

“In principle, the graphene can be tailored to detect a range of different things,” said McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton. “It can be configured to detect DNA or certain viruses. Here, we detect a single bacterium.”

By combining the graphene array with a small antenna, the detection can be picked up by a remote reader device that is small enough to be held in a user’s hand.