Scientists at Princeton University in New Jersey used silk strands and tiny gold wires bundled with graphene to create a removable tattoo that adheres to dental enamel and could eventually be used to monitor a patient’s health with unprecedented sensitivity.

They demonstrated its wireless capability by having a student breathe across a sensor attached to a cow’s tooth and, immediately, the sensor responded to the breath, transmitting signal to a nearby monitor.

Using graphene allowed the researchers to construct a small, flexible device able to detect bacteria at a much higher sensitivity level than traditional methods. By combining the graphene array with a small antenna, the detection can be picked up by a remote reader device small enough to be held in a user’s hand.

The research team imprinted tiny graphene sensors onto an thin film of water-soluble silk, then used a stencil-mask assisted evaporation technique to pattern an antenna made of thin gold strands onto the silk film and connect it to the sensors. The complete device looks like a common removable tattoo. The sensor can be attached to a person’s tooth or skin. When washed with water, the silk base dissolves, but the graphene sensor and the antenna remain securely fastened. The antenna coil transmits the signal without the need for a battery.

In tests, the researchers detected samples of bacteria that can cause surgical infections and others that can lead to stomach ulcers. It can be configured to detect DNA, certain viruses, and even a single bacterium.