The EES designs yield flat devices that are less than 50-microns thickthinner than the diameter of a human hairwhich are integrated onto the polyester backing familiar from stick-on tattoos.
The devices are so thin that close-contact forces called van der Waals interactions dominate the adhesion at the molecular level, so the electronic tattoos adhere to the skin without any glues and stay in place for hours. The recent study demonstrated device lifetimes of up to 24 hours under ideal conditions.
"The mechanics behind the design for our serpentine-shaped electronics makes the device as soft as the human skin," says Northwestern University engineer Yonggang Huang, also a lead researcher on the project. "The design enables brittle, inorganic semiconductors to achieve extremely vast stretchability and flexibility. Plus, the serpentine design is very useful for self adhesion to any surface without using glues."
While some areas of the body are ill-suited to adhesive electronics, such as the elbow, most regions commonly targeted for medical and experimental studies are ideal, including the forehead, extremities and the chest.
Regions of the body that previously proved difficult to fit with sensors may now be monitored, including the throat, which the researchers studied to observe muscle activity during speech.
The throat experiment yielded enough precision for the research team to differentiate words in vocabulary and even control a voice-activated video game interface with greater than 90 percent accuracy.
"This type of device might provide utility for those who suffer from certain diseases of the larynx," adds Rogers. "It could also form the basis of a sub-vocal communication capability, suitable for cov
|Contact: Josh Chamot|
National Science Foundation