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Stretchable temperature-sensing circuits with strain suppression based on carbon nanotube transistors

Abstract

For the next generation of wearable health monitors, it is essential to develop stretchable and conformable sensors with robust electrical performance. These sensors should, in particular, provide a stable electrical output without being affected by external variables such as induced strain. Here, we report circuit design strategies that can improve the accuracy and robustness of a temperature sensor based on stretchable carbon nanotube transistors. Using static and dynamic differential readout approaches, our circuits suppress strain-dependent errors and achieve a measured inaccuracy of only ±1 oC within a uniaxial strain range of 0–60%. We address device variability by using a one-time, single-point calibration approach. In contrast with previous approaches, which infer temperature change through a normalized measurement at two temperatures, our prototype devices provide an absolute output without temperature cycling. This is essential for practical deployment because heating and cooling the sensor is prohibitively slow and costly during real-time operation and production testing.

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Fig. 1: Stretchable integrated circuit for strain-independent temperature sensing.
Fig. 2: Stretchable SWCNT TFTs for circuits.
Fig. 3: Temperature dependence of the stretchable TFT devices.
Fig. 4: Performance of stretchable temperature sensors based on static differential sensing circuit architecture.
Fig. 5: Performance of stretchable temperature sensors based on dynamic differential sensing circuit architecture.

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Acknowledgements

The authors thank M. Claus for helpful discussion on compact model development and F. Lian for the help of collecting SEM images. This work was supported by Samsung Electronics. R.P. acknowledges support from Marie Curie Cofund, Beatriu de Pinós fellowship (AGAUR 2014 BP-A 00094). A.C.H. acknowledges support from the National Science Foundation Graduate Research Fellowship (grant no. DGE-1147474).

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Contributions

C.Z. and B.M. conceived the concept. C.Z., B.M. and Z.B. conceived the experiments. C.Z., A.C., Y.W. and T.L. developed the fabrication processes. C.Z. and R.P. performed data collection and analysis of temperature-dependence for transistors. A.C.H., C.Z. and J.Y.O. designed the test station with strain and temperature. X.Y. and I.P. synthesized the supramolecular sorting polymer. J.W.-F.T. collected SEM images. Z.B. and B.M. supervised the project. All authors provided comments for the manuscript.

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Correspondence to Zhenan Bao or Boris Murmann.

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The authors declare no competing interests.

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Supplementary information

Supplementary Information

Supplementary Figures 1–11 and Supplementary Table 1

Supplementary Video 1

Demonstration of stretchable temperature sensor attached to the knuckle area of a flexible rubber prosthetic hand

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Zhu, C., Chortos, A., Wang, Y. et al. Stretchable temperature-sensing circuits with strain suppression based on carbon nanotube transistors. Nat Electron 1, 183–190 (2018). https://doi.org/10.1038/s41928-018-0041-0

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