2004 Fiscal Year Final Research Report Summary
Development of micro-PIV for electmosmotic flow measurement
| Project/Area Number |
14350089
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
OSHIMA Marie The University of Tokyo, Institute of Industrial Science, Associate Professor, 生産技術研究所, 助教授 (40242127)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Toshio Japan Automobile Research Institute, President (Researcher), 所長(研究職) (50013206)
TANIGUCHI Nobuyuki The University of Tokyo, Information Technology Center, Professor, 情報基盤センター, 教授 (10217135)
SAGA Tetsuo The University of Tokyo, Institute of Industrial Science, Assistant, 生産技術研究所, 助手 (30013220)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Micro-PIV / Electroosmotic flow / Micro-TAS / Zeta-potential / Microchannel / Depth-of-field / Measurement depth / Confocal micro-PIV |
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| Research Abstract |
A new micro flow diagnostic technique, "micro-PIV", has been developed in order to investigate the electroosmotic flow, which is generated by electrical force in microfluidic devices or systems such as "μTAS". The micro-PIV system consists of a custom-built epifluorescent microscope and several conventional PIV components such as a high-sensitive cooled CCD camera, a high-power pursed laser, synchronizer, PC and so on. Using this optical system and PIV method, any micro flows in the fields of 510 μm x 410 μm can be visualized readily and measured quantitatively with high-spatial resolution. The key features of the present system are reflected-light illumination method with pursed lasers and long working distance, which help to increase the ease of use and expand the application range of the micro-PIV system.
The micro-PIV system has been applied to the measurement of various microchannel flows for the purpose of measurement performance evaluation. And then, we measured the electroosmoti
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c flow using the micro-PIV system and evaluated the effects of zeta-potential of both tracer particles and channel surfaces on the flow. The following considerations are derived from the results of PIV and zeta-potential measurements. Firstly, electroosmotic flow in a microchannel shows flat velocity profiles except near the wall. Secondly, electroosmotic flow arises in a PDMS channel even though it assumed to be electrically neutral. Finally, the ion density and the potential (including zeta-potential) in the electrical double layer vary according to additional tracer particles, which leads to changes in electroosmotic velocity profiles. The micro-PIV technique, however, has a disadvantage in obtaining a good quality of particle images. The general micro-PIV system makes use of the epifluorescent microscopy so as to image the tracer particles. Therefore, the micro-PIV images always include projection of whole fluorescent light from not only the focused particles but also the unfocused particles, which decreases the out-of-plane measurement resolution.
In order to improve the out-of-plane resolution of micro-PIV, we have developed a new micro-PIV technique, "confocal micro-PIV". Using this confocal micro-PIV system, we can remove the out-of-focus light optically from PIV images and measure velocity distributions within a thin layer of a horizontal cross-sectional plane. As the demonstration of confocal micro-PIV, we have measured the internal flow of the small droplet, and found out three-dimensional flow structure inside the droplet. The confocal micro-PIV technique has proved to be a useful and powerful tool for the experimental study of the electroosmotic flow phenomenon. Less
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