Electronic tattoos: the most multifunctional but imperceptible wearables

Wearable electronics are finding emerging applications in mobile health, rehabilitation, prosthetics/exoskeletons, athletic training, human-machine interaction, etc. However, our skin is soft, curvilinear and dynamic whereas wafer-based electronics are hard, planar, and rigid. As a result, state-of-the-art wearables can only be strapped or clipped on human body. The development of flexible and stretchable electronics offers a remedy for such challenge. E-tattoos represent a class of stretchable circuits, sensors, and actuators that are ultrathin, ultrasoft, skin-conformable and deformable just like a temporary tattoo. We introduce a low-cost, dry and freeform “cut-and-paste” and “cut-solder-paste” method invented by my lab to fabricate e-tattoos. This method has been proved to work for thin film metals, polymers, ceramics, as well as 2D materials. Using these method, we created the first truly imperceptible e-tattoos based on graphene, and modular and reconfigurable Bluetooth and NFC enabled wireless e-tattoos.