A new method for creating highly flexible, tattoo-like circuits has been developed by researchers from Carnegie Mellon University and the University of Coimbra of Portugal that could one day power wearable devices.

The process uses a trace of an electrically conductive, liquid metal alloy that is applied to tattoo paper that adheres to human skin. The ultra-thin electronic tattoos can be applied with water, the same way a child’s decorative tattoo is applied with a damp sponge.

Flexible, ultra-thin electronic tattoos could be used in robotics or wearables of the future. Source: Carnegie MellonResearchers said other electronic tattoos either require complex fabrication techniques inside a cleanroom or lack the material required to be stretchable and function correctly on skin. The Carnegie Mellon method works by directly printing stretchable electronic circuits through technology developed by the University of Coimbra.

"This is a breakthrough in the printed electronics area," said Mahmoud Tavakoli, director of the Soft and Printed Microelectronics Lab at the University of Coimbra. "We showed for the first time that inkjet-printed patterns of silver nanoparticles can be sintered at room temperature using the gallium indium alloy. Removing the need for high temperature sintering makes our technique compatible with thin-film and heat sensitive substrates."

The process is low cost and includes mechanical properties similar to lightweight fabrics so they can bend, fold, twist and resist strains above 30%, which is the typical stretchability of human skin, researchers said.

Carnegie Mellon said the ultra-thin electronic tattoos could be used in epidermal biomonitoring, soft robotics, flexible displays and 3D-transferable printed electronics.

The full research can be found in the journal Advanced Materials.