Low-cost, μm-thick, tape-free electronic tattoo sensors with minimized motion and sweat artifacts

Electronic tattoos (e-tattoos), also known as epidermal electronics, are ultra-thin and ultra-soft noninvasive but skin-conformable devices with capabilities including physiological sensing and transdermal stimulation and therapeutics. The fabrication of e-tattoos out of conventional inorganic electronic materials used to be tedious and expensive. Recently developed cut-and-paste method has significantly simplified the process and lowered the cost. However, existing cut-and-paste method entails a medical tape on which the electronic tattoo sensors should be pasted, which increases tattoo thickness and degrades its breathability. To address this problem, here we report a slightly modified cut-and-paste method to fabricate low-cost, open-mesh e-tattoos with a total thickness of just 1.5 μm. E-tattoos of such thinness can be directly pasted on human skin and conforms to natural skin texture. We demonstrate that this ultra-thin, tape-free e-tattoo can confidently measure electrocardiogram (ECG), skin temperature, and skin hydration. Heart rate and even respiratory rate can be extracted from the ECG signals. A special advantage of such ultra-thin e-tattoo is that it is capable of high-fidelity sensing with minimized motion artifacts under various body movements. Effects of perspiration are found to be insignificant due to the breathability of such e-tattoos.Flexible electronics: cutting plotters cut costs of electronic tattoosTattoos able to record heart rate and skin conditions have been fabricated with a low-cost cutting plotter. An international collaboration led by YongAn Huang and Nanshu Lu from the Huazhong University of Science and Technology in Wuhan, China, and the University of Texas at Austin, USA, have used this tool—a computer-controlled knife commonly employed to cut paper, vinyl and other materials in custom shapes—to define metallic serpentines on a plastic layer deposited on tattoo paper. The layer is so thin—about one thousandth of a millimeter—that the whole device is imperceptible when transferred on the skin, yet it adheres perfectly without blocking normal perspiration. Applied to human chest, these inexpensive metallic sensors monitor key health parameters, such as skin temperature and heart electric signal, without being affected by sweat and motion artefacts.