Abstract
Wearable electronics with great breathability enable a comfortable wearing experience and facilitate continuous biosignal monitoring over extended periods1,2,3. However, current research on permeable electronics is predominantly at the stage of electrode and substrate development, which is far behind practical applications with comprehensive integration with diverse electronic components (for example, circuitry, electronics, encapsulation)4,5,6,7,8. Achieving permeability and multifunctionality in a singular, integrated wearable electronic system remains a formidable challenge. Here we present a general strategy for integrated moisture-permeable wearable electronics based on three-dimensional liquid diode (3D LD) configurations. By constructing spatially heterogeneous wettability, the 3D LD unidirectionally self-pumps the sweat from the skin to the outlet at a maximum flow rate of 11.6 ml cm−2 min−1, 4,000 times greater than the physiological sweat rate during exercise, presenting exceptional skin-friendliness, user comfort and stable signal-reading behaviour even under sweating conditions. A detachable design incorporating a replaceable vapour/sweat-discharging substrate enables the reuse of soft circuitry/electronics, increasing its sustainability and cost-effectiveness. We demonstrated this fundamental technology in both advanced skin-integrated electronics and textile-integrated electronics, highlighting its potential for scalable, user-friendly wearable devices.
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Data availability
All data supporting the results of this study are available in the paper and its Supplementary Information. Source data are provided with this paper.
Code availability
Custom codes for raw electrocardiogram signal collection are available at https://doi.org/10.5281/zenodo.10575185.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (grant no. 62122002), City University of Hong Kong (grant nos. 9667221, 9678274 and 9610444), as part of the InnoHK Project 2.2–AI-based 3D ultrasound imaging algorithm at Hong Kong Centre for Cerebro-cardiovascular Health Engineering (COCHE), the Research Grants Council of the Hong Kong Special Administrative Region (grants nos. 11213721, 11215722, 11211523 and RFS2324-1S03), Shenzhen Science and Technology Innovation Commission (grant no. SGDX20220530111401011) and the RGC Senior Research Fellow Scheme (SRFS2122-5S04).
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Contributions
X.Y. and B.Z. conceived the idea and designed the projects. B.Z. designed the whole system and conducted overall experiments. B.Z. and Jiy.L. designed the liquid diode. J.Z. designed the circuits. L.C. and B.Z. conducted the mechanical modelling. Q.Z. and B.Z. carried out the cytotoxicity test. Jiy.L., Z.M. and B.Z. conducted the fluid simulation. F.C., L.C. and X.H. performed the materials characterization. Y.Y., C.K.Y., Jia.L., P.W., S.J., H.L., D.L., Y.L., K.Y., R.S. and Z.C. assisted in the fabrication and testing experiments. B.Z., L.C., Y.H., G.Z., J.Z., Jiy.L. and Y.G. organized the user study. B.L.K., W.Y., F.W., Z.Z. and Z.W. evaluated the experiments and contributed valuable ideas. B.Z. and X.Y. wrote the manuscript. All authors discussed the results and commented on the manuscript.
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Nature thanks Nanshu Lu, Sheng Xu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended data figures and tables
Extended Data Fig. 1 Contact angle of the selective plasma-treated fabric under various treatment conditions.
a, Schematic illustration of the fabric samples for selective plasma treatment. b, Contact angle of the channels with mask size from 0.2 to 1.5 mm on both top (T) and back (B) sides of the superhydrophobic fabric after plasma treatment for 0.5 to 10 min.
Extended Data Fig. 2 Fluid simulation of the 3D LD.
a, Velocity magnitude. b, Streamlines. c, Pressure contours. d, Spatiotemporal variation in the liquid volume fraction.
Extended Data Fig. 3 Cytotoxicity test of the VLD and 3D LD.
a, LIVE/DEAD staining (green, live cell; red, dead cell). Scale bars, 100 μm. b,c, Cell viability (b) and optical density (OD) values (c) obtained in the in vitro cytotoxicity assay. Bar height, mean; error bars, s.d.; n = 3 independent samples.
Extended Data Fig. 4 Evaluation of skin temperature beneath various patches.
a, Sequential arrangement of patches from left to right: commercial ECG electrodes (1), PDMS (2), VLD (3) and 3D LD (4). Scale bar, 5 cm. b, Outline of the test procedure. c,d, Photographic and infrared images of skin pre-exercise and post-exercise (PE) with different patches applied. Scale bars, 5 cm.
Extended Data Fig. 5 Optical images and FEA modelling of the permeable ECG monitor under stretching, bending and twisting.
a, Optical images. b, FEA modelling. Scale bars, 1 cm.
Extended Data Fig. 6 Comparison of motion artefacts between the conventional cable-connected type and our wearable device.
a–d, Raw ECG data (a,b) and post-processed data (c,d) from the commercial electrode connected with the DAQ and our device under resting, walking and jumping conditions. ECG data from the DAQ were lost under walking and jumping conditions, whereas our device maintained stable ECG signal readout under body motion.
Extended Data Fig. 7 Continuous ECG recording during a 30-min cycling workout.
a, ECG signals from the cable-connected DAQ are difficult to discern during the cycling process. b, Continuous ECG signals from our wearable and permeable device. The HR and QTO are calculated simultaneously and continuously. c, Enlarged view of the ECG signal, HR and QTO during the cycling and rest periods.
Extended Data Fig. 8 Comparative assessment of the thermal comfort provided by commercial ECG electrodes and our permeable ECG monitor.
Three volunteers were asked to wear both the commercial electrodes and our device while continuously cycling for 30 min. Infrared images of the skin are captured immediately after patch removal and following a 5-min rest. The maximum temperature beneath the commercial electrodes was nearly 1.9 °C higher than that beneath our device. Scale bars, 5 cm.
Extended Data Fig. 9 ECG monitoring by the permeable patch before and after running.
a,b, Optical images of the patches attached to the chest before (a) and after (b) exercise. Scale bars, 5 cm. c, Optical image depicting the condition of skin beneath the device. Scale bar, 1 cm. d, Optical image demonstrating the sweat-discharging channels of the device. Scale bar, 1 cm. e,f, ECG signals acquired before (e) and after exercise (f).
Extended Data Fig. 10 Four-layer integrated circuit.
a, Exploded schematic illustrating the layer-by-layer structure. b, Photographic image of the integrated circuit. Scale bar, 1 cm. c,d, Images of the permeable device affixed to the chest (c) and forearm (d) for ECG (c) and EMG (d) signal acquisition, alongside the recorded ECG (c) and EMG (d) traces. Scale bars, 6 cm.
Supplementary information
Supplementary Video 1
Anti-gravity sweat transport of the VLD.
Supplementary Video 2
Directional sweat transport of the HLD.
Supplementary Video 3
Fluid simulation of the 3D LD.
Supplementary Video 4
Gas and sweat permeability of the PDMS and 3D LD.
Supplementary Video 5
Deformation of the wearable sweat-permeable ECG monitor.
Supplementary Video 6
Demonstration of the sweat-permeable ECG monitor.
Supplementary Video 7
Continuous ECG monitoring during daily activities and exercise.
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Zhang, B., Li, J., Zhou, J. et al. A three-dimensional liquid diode for soft, integrated permeable electronics. Nature 628, 84–92 (2024). https://doi.org/10.1038/s41586-024-07161-1
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DOI: https://doi.org/10.1038/s41586-024-07161-1
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