Available on-demand - *S.SM04.03.03
Wireless Modular E-Tattoos Chargeable On-the-Go
University of Texas at Austin1
Soft, noninvasive and multifunctional epidermal electronics (a.k.a. electronic tattoos or e-tattoos) have demonstrated many exciting applications in mobile health, athletic training, human-machine interface (HMI) and so on. However, e-tattoos are only practically useful when they are low cost and wireless. Previously, our group has invented a dry and digital manufacturing approach named the “cut-and-paste” method for the rapid prototyping of e-tattoo sensors using a paper/vinyl cutter plotter . This method has been demonstrated to work for thin film metals [1, 2], various polymer sheets [1, 3], ceramics , as well as 2D materials such as graphene [5, 6]. The cut-and-pasted e-tattoos are low cost and can be used to measure a variety of physiological signals such as electrocardiogram (ECG), seismocardiogram (SCG), electrooculogram (EOG), skin hydration, skin temperature, respiratory rate and so on [1-3, 5, 6]. To make the e-tattoos go wireless, we now report the “cut-solder-paste” process to incorporate integrated circuits (ICs) for signal readout and processing, near field communication (NFC) , as well as Bluetooth transmission . To overcome the limited patterning resolution of the cutter plotter and to recycle the tattoo layers with ICs, we propose a modular concept in which the wireless charging layer (NFC layer), the wireless communication layer (Bluetooth layer), the readout circuit layer, and the sensor/electrode layer are fabricated individually and stacked up at the final step of fabrication. The thickness of a fully assembled multilayer e-tattoo (excluding IC chips) is less than 300 um and the overall stretchability is still beyond 20%. In addition to already mentioned capabilities, such e-tattoos can also wireless track motion, mechano-acoustic heart signals, and oxygen saturation (SpO2) [3, 7, 8]. The NFC-enabled e-tattoos can be wirelessly charged so no battery is needed but the sampling rate is limited to 25 Hz and the wireless communication distance is limited to 5 cm. The Bluetooth-enabled e-tattoos require on-tattoo batteries but the sampling rate can be up to 4 kHz and the wireless communication range can be up to 10 m. Combining the NFC layer and the Bluetooth layer in one e-tattoo, we demonstrate that such wireless e-tattoo can also be wirelessly charged on-the-go via stretchable fabric feeding coils , enabling long-term, ambulatory and continuous sensing. Moreover, we propose that different layers can be disassembled and reassembled multiple times. After disassembly, the electrode layer should be disposed but the other layers can be reassembled into new e-tattoos. The low-cost, rapid prototyping method together with the wireless and reconfigurable capabilities represent exciting advancement towards practically useful wireless e-tattoos.
1. Yang, S., et al., "Cut-and-Paste" Manufacture of Multiparametric Epidermal Sensor Systems. Advanced Materials, 2015. 27(41): p. 6423–6430.
2. Wang, Y., et al., Low-cost, μm-thick, tape-free electronic tattoo sensors with minimized motion and sweat artifacts. npj Flexible Electronics, 2018. 2(1): p. 6.
3. Ha, T., et al., A chest-laminated ultrathin and stretchable e-tattoo for the measurement of electrocardiogram, seismocardiogram, and cardiac time intervals. Advanced Science, 2019: p. 1900290.
4. Yang, S., E. Ng, and N. Lu, Indium Tin Oxide (ITO) Serpentine Ribbons on Soft Substrates Stretched beyond 100%. Extreme Mechanics Letters, 2015. 2: p. 37-45.
5. Ameri, S.K., et al., Imperceptible Electrooculography Graphene Sensor System for Human-Robot Interface npj 2D Materials and Applications, 2018. 2: p. 19.
6. Ameri, S.K., et al., Graphene Electronic Tattoo Sensors. Acs Nano, 2017. 11(8): p. 7634-7641.
7. Jeong, H., et al., Modular and Reconfigurable NFC-Enabled Wireless Electronic Tattoos for Biometric Sensing. Advanced Materials Technologies, 2019: p. 1900117.
8. Jeong, H., Huang, Yi., et al., Wireless E-Tattoos Chargeable On-The-Go. To be submitted, 2019.