It’s not often that tattoos are thought of as being as functional as they are decorative, but a group of researchers at UT-Austin are about to change that.

They are developing “e-tattoos” which can be applied to the skin to measure a variety of different things, from electrical to biochemical signals, said Nanshu Lu, an aerospace engineering and engineering mechanic associate professor and one of the primary researchers in this project.

“For our graphene e-tattoo, we have demonstrated that it can measure electrophysiological signals, skin temperature and skin hydration,” Lu said.

Graphene is a single-layer hexagonal lattice of carbon atoms, she added. It’s considered the “wonder material” of the 21st century because of its exotic electronic properties, according to Lu. The material was chosen for the tattoo because of its electrical conductivity, mechanical robustness, atomic thinness and transparency.

It’s the first ultrathin, optically transparent and stretchable sensor made of 2-D material, added Shideh Kabiri Ameri, an electrical engineering postdoctoral associate and a major contributor to the project.

This tattoo has been in development since 2015, Lu said. According to UT News, the group developed a cost and time-effective “cut and paste” method to create e-tattoos.

“At that time, we were using polymer-supported metal sheets as electrodes and sensors, but their thickness are usually more than ten micrometers and they are not transparent,” Lu said.

It was well known that 2D materials are only one atom layer thick and transparent, so Lu’s lab collaborated with electrical and computer engineering associate professor Deji Akinwande, who is a pioneer of 2D materials, to create mechanically and optically imperceptible tattoos.

“The ultra low thickness of graphene allows thinning the sensors to achieve full conformability to skin, and consequently high sensing quality,” Ameri said.

The thinness of the tattoos makes them easy to apply to the skin, and they can be transferred onto the skin just like a temporary tattoo, Ameri said. The transfer process takes less than a minute, is chemical free and requires only water.

Current conventional medical electrodes are gel-based, thick, dry out over time and can be irritating to skin, Lu said. But graphene e-tattoos are a dry electrode, more breathable, and have a multiple-day wear time, while still having comparable signaling accuracy to the gel-electrodes.

“It paves the way for future ‘wear-and-forget’ wearable and medical devices,” Lu said.

Instead of placing conventional, bulky medical electrodes on the heart to measure electrocardiograms, or on the brain to measure electroencephalograms, these devices would be nearly imperceptible to the wearer.

But there are still some obstacles that must be overcome before the tattoos become mainstream.

“Graphene is too thin to reliably integrate with other rigid electronic components,” Lu said. “There are still many engineering difficulties to make a real product out of it, but our work demonstrates a possibility.”

However, the overall sentiment is that there is a lot of promise to the tattoo and its uses.

The group is especially proud of the tattoo’s “wet transfer, dry patterning” method, its viability and low cost, Lu added.

“There has been a lot of interest from scientific and industrial communities,” Ameri said. “We are very excited about the potential for commercialization of such sensors and about the fact that (they) can be accessible (and affordable) in the near future.”