Recently developed flexible mechanosensors based on inorganic silicon1,2,3, organic semiconductors4,5,6, carbon nanotubes7, graphene platelets8, pressure-sensitive rubber9 and self-powered devices10,11 are highly sensitive and can be applied to human skin. However, the development of a multifunctional sensor satisfying the requirements of ultrahigh mechanosensitivity, flexibility and durability remains a challenge. In nature, spiders sense extremely small variations in mechanical stress using crack-shaped slit organs near their leg joints12. Here we demonstrate that sensors based on nanoscale crack junctions and inspired by the geometry of a spider’s slit organ can attain ultrahigh sensitivity and serve multiple purposes. The sensors are sensitive to strain (with a gauge factor of over 2,000 in the 0–2 per cent strain range) and vibration (with the ability to detect amplitudes of approximately 10 nanometres). The device is reversible, reproducible, durable and mechanically flexible, and can thus be easily mounted on human skin as an electronic multipixel array. The ultrahigh mechanosensitivity is attributed to the disconnection–reconnection process undergone by the zip-like nanoscale crack junctions under strain or vibration. The proposed theoretical model is consistent with experimental data that we report here. We also demonstrate that sensors based on nanoscale crack junctions are applicable to highly selective speech pattern recognition and the detection of physiological signals. The nanoscale crack junction-based sensory system could be useful in diverse applications requiring ultrahigh displacement sensitivity.
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This work is dedicated to the late Kahp-Yang Suh, one of the great pioneers of biomimetics. We thank S. J. Kwon for discussion of the theoretical modelling, T. Shin and S. J. Kang for help in relation to speech pattern recognition, K. Park for high-speed camera recording, J.-Y. Lee for LabVIEW programming, J. S. Kim for computational analysis of the audio files, T. Lee for flexibility testing, J. H. Park for playing the violin, and Y. K. Song and J.-P. Kim for their comments about phonetics and spider slit organs, respectively. This work was supported by the Global Frontier R&D Program of the Center for Multiscale Energy Systems (grant nos 2011-0031561 and 2011-0031577) and the Basic Science Research Program (grant no. 2009-0083540), all funded by the National Research Foundation of Korea under the Ministry of Science, ICT and Future Planning and by grants IBS-R015-D1 and NRF-2013-R1A1A1061403 (T.-i.K.).
The authors declare no competing financial interests.
This file contains Supplementary Text, Supplementary Figures 1-24, Supplementary Table 1 and Supplementary References. (PDF 4570 kb)
This video shows time dependent resistance variations measured by our sensor attached to the violin while ‘Salut d’Amour’ is played. They were converted into digital signals from which the real-time peak spectrogram was retrieved (shown in the bottom image of Figure 3c). (AVI 7896 kb)
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Kang, D., Pikhitsa, P., Choi, Y. et al. Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system. Nature 516, 222–226 (2014). https://doi.org/10.1038/nature14002
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