A customizable, low-cost 3D printer has printed electronics on a real hand for the first time, leading the way for next-generational wearable devices. The adaptive printer, which is both autonomous and portable, could be used by soldiers to print temporary chemical sensors on their bodies or charge essential electronics.
"We are excited about the potential of this new 3D-printing technology using a portable, lightweight printer costing less than $400," said Michael McAlpine, the study's lead author, in a statement. "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. It would be like a 'Swiss Army knife' of the future with everything they need all in one portable 3D printing tool."
Unlike typical 3D printers that have to calibrate then print, this one uses monitoring cameras to predict and adjust to small movements in the body in real time by placing temporary markers on the skin while it is being scanned.
"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 McAlpine. "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."
A highly conductive water-soluble ink made of silver flakes conducts and cures at room temperature so that it won’t burn the skin. Ethanol is added to the ink to speed up drying time. Fabricated inductive coils serve to both charge wireless electronic devices and sense moisture, something scientists say could help monitor physical exertion or stress via sweat. The device can stay on the hand for more than two hours, after which point the user can simply peel or wash it off.
In the same study, which is published in Advanced Materials, researchers successfully printed "bioink" – a hydrogel containing biological cells – onto a mouse’s skin wound. They say this could lead to new medical treatments for healing wounds and directly printing grafts for skin disorders.
"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."