Research led by Deji Akinwande and Nanshu Lu at the University of Texas at Austin has demonstrated tattoo-like epidermal sensors as an emerging class of truly wearable electronics, owing to their thinness and softness.
While most wearable electronics are based on thin metal films, a silicon membrane, or nanoparticle-based printable inks, the researchers reported sub-micrometer thick, multimodal electronic tattoo sensors that are made of graphene.
The graphene electronic tattoo (GET) is designed as filamentary serpentines and fabricated by a cost- and time-effective "wet transfer, dry patterning" method. It has a total thickness of 463 ± 30 nm, an optical transparency of ∼85%, and a stretchability of more than 40%. The GET can be directly laminated on human skin just like a temporary tattoo and can fully conform to the microscopic morphology of the surface of skin via just van der Waals forces.
The open-mesh structure of the GET makes it breathable and its stiffness negligible. A bare GET is able to stay attached to skin for several hours without fracture or delamination. With liquid bandage coverage, a GET may stay functional on the skin for up to several days. As a dry electrode, GET-skin interface impedance is on par with medically used silver/silver-chloride (Ag/AgCl) gel electrodes, while offering superior comfort, mobility, and reliability. GET has been successfully applied to measure electrocardiogram (ECG), electromyogram (EMG), electroencephalogram (EEG), skin temperature, and skin hydration.
Source and top image: ACS Nano