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Integrated SWCNT sensors in micro-wind tunnel for air-flow shear-stress measurement

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Abstract

We have developed SWCNT sensors for air-flow shear-stress measurement inside a polymethylmethacrylate (PMMA) “micro-wind tunnel” chip. An array of sensors is fabricated by using dielectrophoretic (DEP) technique to manipulate bundled single-walled carbon nanotubes (SWCNTs) across the gold microelectrodes on a PMMA substrate. The sensors are then integrated in a PMMA micro-wind tunnel, which is fabricated by SU-8 molding/hot-embossing technique. Since the sensors detect air flow by thermal transfer principle, we have first examined the I–V characteristics of the sensors and confirmed that self-heating effect occurs when the input voltage is above ~1 V. We then performed the flow sensing experiment on the sensors using constant temperature (CT) configuration with input power of ~230 μW. The voltage output of the sensors increases with the increasing flow rate in the micro-wind tunnel and the detectable volumetric flow is in the order of 1 × 10−5m3/s. We also found that the activation power of the sensors has a linear relation with 1/3 exponential power of the shear stress which is similar to conventional hot-wire and polysilicon types of convection-based shear-stress sensors. Moreover, measurements of sensors with different overheat ratios were compared, and results showed that sensor is more sensitive to the flow with a higher overheat ratio.

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Acknowledgments

The authors would like to sincerely thank Mandy L. Y. Sin and Gary C. T. Chow from the Centre for Micro and Nano Systems of CUHK for their contributions to this work. Ms. Sin is currently a Ph.D. student at the University of Arizona, USA, and Mr. Chow is currently a Ph.D. student at the Imperial College, UK. This work is funded by the Hong Kong Research Grants Council under Grant No. CUHK/413906 and the Natural Science Foundation of China under Project No. 60675060.

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Authors and Affiliations

  1. Centre for Micro and Nano Systems, The Chinese University of Hong Kong, William M. W. Mong Engineering Building, CUHK, Shatin, N.T., HKSAR, China

    Winnie W. Y. Chow & Wen J. Li

  2. The State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, 114 Nanta Street, Shenyang, China

    Yanli Qu, Wen J. Li & Steve C. H. Tung

  3. Department of Mechanical Engineering, University of Arkansas, 204 Mechanical Engineering, Dickson Street, Fayetteville, AR, 72701, USA

    Steve C. H. Tung

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  1. Winnie W. Y. Chow
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  2. Yanli Qu
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  3. Wen J. Li
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  4. Steve C. H. Tung
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Correspondence to Wen J. Li.

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Chow, W.W.Y., Qu, Y., Li, W.J. et al. Integrated SWCNT sensors in micro-wind tunnel for air-flow shear-stress measurement. Microfluid Nanofluid 8, 631–640 (2010). https://doi.org/10.1007/s10404-009-0495-5

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  • DOI: https://doi.org/10.1007/s10404-009-0495-5

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