Optically sliced measurement of velocity and pH distribution in microchannel
Optically sliced measurement of velocity and pH distribution in microchannel
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DOI：
10.1007/s00348-007-0326-y
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发表时间：
2007-08-01
影响因子：
2.4
通讯作者：
Hishida, Koichi
中科院分区：
文献类型：
--
作者：
Ichiyanagi, Mitsuhisa;Sato, Yohei;Hishida, Koichi
通过使用共焦显微镜和 3CCD 彩色相机开发了速度和 pH 分布的同步测量技术，用于研究微通道中的化学反应流场。微米分辨率粒子图像测速和激光诱导荧光分别用于速度和 pH 测量。本研究采用直径为1μm的荧光颗粒和荧光素钠盐，在pH 5.0-9.0范围内荧光强度随着pH值的增加而增加。本系统的优点是通过使用3CCD彩色相机将颗粒的荧光与染料的荧光分开，并通过共焦显微镜提供5.0μm的深度分辨率。速度和 pH 测量的测量不确定度估计分别为 5.5 μm/s 和 pH 0.23。将两种不同pH值的水溶液引入T形微通道中。通过本技术研究了连接区域的混合过程，并通过比较从实验pH分布获得的质子浓度分布和从测量的速度数据计算的质子浓度分布，讨论了化学反应对pH梯度的影响。对于具有缓冲作用的化学反应流，数值模拟的曲线与实验的曲线相比显示出较小的梯度，因为质子的产生或消失是由化学反应产生的。此外，还根据速度和 pH 分布评估了质子对流，并与扩散进行了比较。研究发现，扩散与对流之间的比率是研究微流体装置中化学反应混合过程的重要因素。
A simultaneous measurement technique for the velocity and pH distribution was developed by using a confocal microscope and a 3CCD color camera for investigations of a chemical reacting flow field in a microchannel. Micron-resolution particle image velocimetry and laser induced fluorescence were utilized for the velocity and pH measurement, respectively. The present study employed fluorescent particles with 1 mu m diameter and Fluorescein sodium salt whose fluorescent intensity increases with an increase in pH value over the range of pH 5.0-9.0. The advantages of the present system are to separate the fluorescence of particles from that of dye by using the 3CCD color camera and to provide the depth resolution of 5.0 mu m by the confocal microscope. The measurement uncertainties of the velocity and pH measurements were estimated to be 5.5 mu m/s and pH 0.23, respectively. Two aqueous solutions at different pH values were introduced into a T-shaped microchannel. The mixing process in the junction area was investigated by the present technique, and the effect of the chemical reaction on the pH gradient was discussed by a comparison between the proton concentration profiles obtained from the experimental pH distribution and those calculated from the measured velocity data. For the chemical reacting flow with the buffering action, the profiles from the numerical simulation showed smaller gradients compared with those from the experiments, because the production or extinction of protons was yielded by the chemical reaction. Furthermore, the convection of protons was evaluated from the velocity and pH distribution and compared with the diffusion. It is found that the ratio between the diffusion and convection is an important factor to investigate the mixing process in the microfluidic device with chemical reactions.