3D printing on human skin possible

Scientists have developed a "revolutionary" new 3D printing technique which could be used to print electronics directly on human skin.

A one-of-a-kind 3D printer built at the University of Minnesota in the US can print touch sensors on a model hand.

"While we have not printed on human skin yet, we were able to print on the curved surface of a model hand using our technique," said Michael McAlpine, associate professor at University of Minnesota.

"We also interfaced a printed device with the skin and were surprised that the device was so sensitive that it could detect your pulse in real time," said McAlpine.

The ultimate wearable technology could eventually be used for health monitoring or by soldiers in the field to detect dangerous chemicals or explosives, researchers said.

McAlpine and his team made the unique sensing fabric with a one-of-a-kind 3D printer they built in the lab.

The multifunctional printer has four nozzles to print the various specialised "inks" that make up the layers of the device - a base layer of silicone, top and bottom electrodes made of a conducting ink, a coil-shaped pressure sensor, and a sacrificial layer that holds the top layer in place while it sets.

The supporting sacrificial layer is later washed away in the final manufacturing process.

All of the layers of "inks" used in the flexible sensors can set at room temperature. Conventional 3D printing using liquid plastic is too hot and too rigid to use on the skin.

These flexible 3D printed sensors can stretch up to three times their original size.

"This is a completely new way to approach 3D printing of electronics," said McAlpine, lead researcher on the study published in the journal Advanced Materials.

"We have a multifunctional printer that can print several layers to make these flexible sensory devices. This could take us into so many directions from health monitoring to energy harvesting to chemical sensing," McAlpine added.