They might sound like something out of a sci-fi novel, but teeth tattoos are actually quite popular these days. Applied to a cap or crown, these images are permanent and come in all shapes and sizes, from pictures of George Washington to sailboats to phrases like “Bite Me.”

Scientists at Princeton and Tufts are taking teeth tattoos in a completely different direction. Instead of ink, they’re using graphene, and it isn’t for art’s sake. These tattoos are actually electronic sensors, and they’re a bacterium’s worst nightmare. Imprinted on silk, the tattoos are placed onto a tooth, and after water washes the silk away the graphene remains and monitors the mouth for bacteria. Powered by electrodes and an inductive coil, the tattoo uses antimicrobial peptides to latch onto germs. Thanks to the electricity in a bacterium’s cell membrane, a signal is sent to a nearby antenna which scientists use to determine what kind of bacteria is crawling around inside your mouth. You still need to brush, though.