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Tattoo-like epidermal sensors are an emerging class of truly wearable electronics owing to their thinness and softness. While most of them are based on thin metal films, silicon membrane, or nanoparticle-based printable inks, we report the first demonstration of sub-micron thick, multimodal electronic tattoo sensors that are made of graphene. The graphene electronic tattoo (GET) is designed with 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%. 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 GET makes it breathable and its stiffness negligible. Bare GET is able to stay attached to skin, for several hours, without fracture or delamination. With liquid bandage coverage, GET may stay functional on skin 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. Graphene represents a new facile route for ultra-conformable multifunctional electronic tattoos, and paves the path for the introduction of other two dimensional materials for future advanced tattoo systems.
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