When you think of digital electronics, you probably think of printed circuit boards, silicon semi-conductor chips, and rigid wires. That’s great technology if you’re creating a smartphone, When you’re trying to create a sensor that will adhere to an organ inside the human body, however, you’ll want something softer and more flexible. That’s precisely the problem that researchers at the University of Manchester and Harvard University were trying to solve: metal-free electrodes that can flex to fit surfaces within the human body.

Their solution uses a hydrogel as a flexible base for printed electrodes. They created an ink based on carbon nanotubes that naturally contact each other to create a conductive channel. The researchers found that adding special graphene flakes — created at the University of Manchester — made the conductors even more flexible and performed better than either nanotubes or graphene by themselves.

The result is a new electrode design that can be used inside or outside the body. By conforming more closely to irregular surfaces, the electrodes can deliver electrical impulses with greater reliability and produce more accurate sensor data.