Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes

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Abstract

Transparent, elastic conductors are essential components of electronic and optoelectronic devices that facilitate human interaction and biofeedback, such as interactive electronics1, implantable medical devices2 and robotic systems with human-like sensing capabilities3. The availability of conducting thin films with these properties could lead to the development of skin-like sensors4 that stretch reversibly, sense pressure (not just touch), bend into hairpin turns, integrate with collapsible, stretchable and mechanically robust displays5 and solar cells6, and also wrap around non-planar and biological7,8,9 surfaces such as skin10 and organs11, without wrinkling. We report transparent, conducting spray-deposited films of single-walled carbon nanotubes that can be rendered stretchable by applying strain along each axis, and then releasing this strain. This process produces spring-like structures in the nanotubes that accommodate strains of up to 150% and demonstrate conductivities as high as 2,200 S cm−1 in the stretched state. We also use the nanotube films as electrodes in arrays of transparent, stretchable capacitors, which behave as pressure and strain sensors.

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Figure 1: Effects of applied strain on films of spray-coated carbon nanotubes on PDMS substrates.
Figure 2: Evolution of morphology of films of carbon nanotubes with stretching.
Figure 3: Use of stretchable nanotube films in compressible capacitors that can sense pressure and strain.
Figure 4: Summary of processes used to fabricate arrays of transparent, compressible, capacitive sensors.
Figure 5: Images showing the characteristics of a 64-pixel array of compressible pressure sensors.

Change history

  • 28 October 2011

    In the version of this Letter originally published online, the colour scale in Fig. 5c should have read 'x10−2'. This has been corrected in all versions of the Letter.

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Acknowledgements

This work was supported by a US Intelligence Community Postdoctoral Fellowship (to D.J.L.) and the Stanford Global Climate and Energy Program. B.C-K.T. was supported by the Singapore National Science Scholarship from the Agency for Science Technology and Research (A*STAR). The authors thank V. Ballarotto for helpful discussions and J.A. Bolander for writing code for the apparatus used for electromechanical measurements.

Author information

D.J.L. and Z.B. conceived the project. D.J.L., M.V. and B.C-K.T. performed and designed the experiments. S.L.H. prepared the materials and developed the conditions used to dope the nanotube films. J.A.L. deposited additional nanotube films. J.A.L. and C.H.F. performed experiments on resistance versus strain. D.J.L., B.C-K.T., M.V., S.L.H. and Z.B. analysed the data. D.J.L. wrote the paper. All authors discussed the results and commented on the manuscript.

Correspondence to Zhenan Bao.

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Lipomi, D., Vosgueritchian, M., Tee, B. et al. Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes. Nature Nanotech 6, 788–792 (2011) doi:10.1038/nnano.2011.184

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