Graphene Electronic Tattoo Sensors

TLDR

Tattoo-like epidermal sensors are an emerging class of truly wearable electronics, prized for their thinness and softness. The authors present sub‑micrometer thick, multimodal electronic tattoo sensors fabricated from graphene. The graphene electronic tattoo (GET) is a filamentary serpentine structure produced by a cost‑effective wet‑transfer, dry‑patterning process that can be laminated directly onto skin, conforming via van der Waals forces and featuring an open‑mesh design that is breathable and nearly unstiff. The GET measures 463 ± 30 nm thick, ~85 % transparent, and >40 % stretchable; it adheres to skin for hours (days with liquid bandage), exhibits impedance comparable to Ag/AgCl gel electrodes while offering superior comfort, mobility, and reliability, and has been used to record ECG, EMG, EEG, skin temperature, and hydration.

Abstract

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, a silicon membrane, or nanoparticle-based printable inks, we report 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.