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Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers

Abstract

The development of an electronic skin is critical to the realization of artificial intelligence that comes into direct contact with humans, and to biomedical applications such as prosthetic skin. To mimic the tactile sensing properties of natural skin, large arrays of pixel pressure sensors on a flexible and stretchable substrate are required. We demonstrate flexible, capacitive pressure sensors with unprecedented sensitivity and very short response times that can be inexpensively fabricated over large areas by microstructuring of thin films of the biocompatible elastomer polydimethylsiloxane. The pressure sensitivity of the microstructured films far surpassed that exhibited by unstructured elastomeric films of similar thickness, and is tunable by using different microstructures. The microstructured films were integrated into organic field-effect transistors as the dielectric layer, forming a new type of active sensor device with similarly excellent sensitivity and response times.

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Figure 1: Fabrication of microstructured PDMS films.
Figure 2: Characterization of the capacitive pressure response of microstructured PDMS films.
Figure 3: Pressure response of an organic transistor with a microstructured PDMS dielectric layer.
Figure 4: Plastic and flexible pixel-type pressure-sensor arrays.

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Acknowledgements

The authors thank J. Locklin for discussions. We thank N. Sutardja and J. Opatkiewicz for help during the development of the microstructuring technology and the first sensor prototypes. This project was partially funded by NSF ECCS 0730710 and MURI Office of Naval Research (N000140810654). We thank the Center for Polymer Interface Macromolecular Assemblies (CPIMA) for the use of shared facilities. We also acknowledge the use of the Stanford Nanocharacterization Laboratory and the Stanford Nanofabrication Facility, partially supported by the National Science Foundation through the National Nanotechnology Infrastructure Network. Part of this work was done at the Stanford Synchrotron Radiation Laboratory (SSRL), operated by the Department of Energy. S.C.B.M. acknowledges postdoctoral fellowship support by the Deutsche Forschungsgemeinschaft (DFG) grant MA 3342/1-1. B.C-K.T. acknowledges support from a National Science Scholarship from the Agency for Science, Technology and Research (A*STAR), Singapore. R.M.S. acknowledges support from a National Science Foundation Graduate Fellowship. Z.B. acknowledges support from a Sloan Research Fellowship.

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Authors

Contributions

Z.B. and S.C.B.M. conceptualized and directed the research project. S.C.B.M. developed the first working sensor prototypes. B.C-K.T. developed large portions of the experimental set-ups. S.C.B.M and B.C-K.T. discussed and carried out the majority of the experiments. B.C-K.T. and C.V.H-H.C designed and fabricated the matrix sensor. B.C-K.T. carried out the temperature drift and loading/unloading stability experiments. R.M.S. took the SEM data. S.B. helped with some experiments. R.M.S., B.C-K.T. and B.V.O.M fabricated the Si moulds. B.V.O.M. fabricated the photolithographic mask. A.N.S. and B.C-K.T carried out most of the bending-stability experiments. C.R. and B.C-K.T. grew the rubrene crystals. S.C.B.M. wrote the first draft of the manuscript. All authors discussed the results and commented on the manuscript.

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Correspondence to Zhenan Bao.

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Mannsfeld, S., Tee, BK., Stoltenberg, R. et al. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nature Mater 9, 859–864 (2010). https://doi.org/10.1038/nmat2834

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