The line between human and robot is becoming increasingly blurred, with the latest breakthrough opening a new frontier in the field of skin electronics.

There has been plenty of talk about incredibly flexible, wearable devices being developed from wonder materials such as graphene, but what if we could skip the wearable part and actually carry electronics within us?

That’s the vision of a team of researchers from the University of Minnesota that has found a way to print customisable electronics right on to the surface of a person’s skin.

In a paper published to Advanced Materials, the team revealed how it altered a low-cost 3D printer built with a technique that allows it to adjust to the smallest movements of the body during printing.

This is achieved by placing temporary markers on the skin, scanning it and then using the printer’s built-in computer vision to adjust to movements in real time.

“No matter how hard anyone would try to stay still when using the printer on the skin, a person moves slightly and every hand is different,” said Michael McAlpine, the study’s lead author.

“This printer can track the hand using the markers and adjust in real time to the movements and contours of the hand, so printing of the electronics keeps its circuit shape.”

What also makes the new printing technique rather special is that it uses a specialised ink made of silver flakes that can cure and conduct at room temperature. This is important as standard 3D printers need to cure at high temperatures of around 100C, which would obviously burn a person’s hand.

Can be peeled off

Once the person needs to remove the electronics from their skin, they just peel it off with a set of tweezers or even just wash it off with water.

“We imagine that a soldier could pull this printer out of a backpack and print a chemical sensor or other electronics they need directly on the skin,” McAlpine said.

“It would be like a Swiss Army knife of the future, with everything they need all in one portable 3D-printing tool.”

Its use is also not limited to electronics, he added, saying that among its applications is the ability to print cells to help people with skin diseases.

During testing, the team successfully used a bio-ink to print cells on a mouse skin wound.

“I’m fascinated by the idea of printing electronics or cells directly on the skin,” McAlpine said. “It is such a simple idea and has unlimited potential for important applications in the future.”