|Silver nanoparticles / Photo by 123rf.com|
In soft electronics, developing highly-flexible tattoo-like circuits usually require multiple techniques. But engineers at Carnegie Mellon University were able to create stretchable electronic tattoos for wearable computing.
The new flexible tattoo circuit was produced by Carmel Majidi, an associate professor of mechanical engineering, and his team. They used a commercially available printer to produce the highly flexible and robust circuitry. Meanwhile, the flexible tattoo contains trace amounts of a liquid metal alloy so it will attach to the human skin.
Their stretchable device was made of silver nanoparticles and a paper for temporary tattoos, printed via a desktop inkjet printer. The nanoparticles have been coated with a thin layer of gallium indium alloy that enhanced the electrical conductivity and mechanical strength of the circuit.
With this said mechanical strength, the circuit can withstand bends, folds, strains, and twists, and can retain its functionality. However, the circuit can only take up to 30 percent of maximum strain to remain functional.
The flexible, ultrathin electronic tattoo can easily be applied onto the skin using water, similar to the application of a children’s tattoo with a damp sponge. Since the robust and stretchable circuit can be produced at a low-cost, the engineers see its potential in numerous applications such as in biomonitoring devices for the skin, flexible screen displays, 3D transferable printed electronics, and soft robotics.
“Our technique is simple. We use a desktop inkjet printer to print traces of silver nanoparticles on temporary tattoo paper… The tattoos are ultrathin, very stretchable, and inexpensive to produce,” said Majidi, a pioneer in the field of soft electronics.
The engineers who developed the flexible circuit collaborated with Soft Machines Labs at CMU and the Institute of Systems and Robotics at the University of Coimbra.