New graphene electronic tattoos can be applied with water

Scientists have designed a graphene-based electronic tattoo that can be directly applied on the skin with water, and may help measure the electrical activity of the heart, brain and muscles.
The graphene tattoos may offer promising replacements for existing medical sensors, which are typically taped to the skin and require gel or paste to enable the electrodes to function, researchers said.
Since the ultrathin graphene tattoos can fully conform to the skin, they offer medical-grade data quality, in contrast with the lower performance of the rigid electrode sensors mounted on bands and strapped to the wrist or chest.
"The graphene tattoo is a dry physiological sensor which, because of its thinness, forms an ultra-conformal contact to skin, resulting in increased signal fidelity," said Shideh Kabiri Ameri from the University of Texas at Austin in the US.

The new tattoos are made of graphene that is coated with an ultrathin backing layer of transparent polymer poly(methyl methacrylate) (PMMA).
During fabrication, the graphene/PMMA bilayer is transferred to a piece of ordinary tattoo paper, and the bilayer is then carved into different patterns of serpentine ribbons to make different types of sensors.

The finished tattoo is then transferred to any part of the body by bringing the graphene side in contact with the skin and applying water to the back of the tattoo paper to release the tattoo, 'Phys.Org' reported.
The tattoos retain their full function for around two days or more, but can be peeled off by a piece of adhesive tape if desired.

Since the researchers previously showed that, theoretically, a graphene tattoo must be less than 510 nanometres (nm) thick to fully conform to human skin and exhibit optimal performance, the tattoo they fabricated here is just 460 nm thick.
Tests showed that the graphene electronic tattoos can be successfully used to measure a variety of electrophysiological signals, including skin temperature and skin hydration, and even the electrical activity of the heart, muscles, and brain.
The research was published in the journal ACS Nano.