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A transparent bending-insensitive pressure sensor

Abstract

Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of 20 ms), large-area, normal pressure monitoring under different, complex bending conditions.

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Figure 1: Transparent pressure-sensitive nanofibre.
Figure 2: Electrical properties of a pressure-sensitive nanofibre and performance under bending.
Figure 3: Pressure-sensor integration with an organic-transistor-driven active matrix.
Figure 4: Measurement of pressure propagation speed in an artificial cardiac system.

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Acknowledgements

This work was supported by a Japan Science and Technology Agency (JST) Someya Bio-Harmonized ERATO grant. The authors thank W. Yukita and B. Hwang for supporting the experiment.

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Authors

Contributions

Sungwon L., A.R., J.R., Sunghoon L., H.J. and T.So. performed the device design and fabrication. T.Y., T.I. and Y.A. performed electric and structural characterization of devices. Q.L. and Z.S. performed numerical analysis of the strain. T.Y. contributed the material analysis tools. T.Se helped with material design and fabrication. Sungwon L., A.R., J.R. and T.So. discussed and prepared the manuscript with input from all co-authors. T.So. supervised the project.

Corresponding author

Correspondence to Takao Someya.

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The authors declare no competing financial interests.

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Lee, S., Reuveny, A., Reeder, J. et al. A transparent bending-insensitive pressure sensor. Nature Nanotech 11, 472–478 (2016). https://doi.org/10.1038/nnano.2015.324

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