3D imaging of flow patterns in an internally-pumped microfluidic device: redox magnetohydrodynamics and electrochemically-generated density gradients.
3D imaging of flow patterns in an internally-pumped microfluidic device: redox magnetohydrodynamics and electrochemically-generated density gradients.
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DOI：
10.1021/ac3036926
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发表时间：
2013-05-07
影响因子：
7.4
通讯作者：
Heyes, Colin D.
中科院分区：
文献类型：
--
作者：
Gao, Feng;Kreidermacher, Adam;Fritsch, Ingrid;Heyes, Colin D.
氧化还原磁流体动力学（MHD）是一种很有前途的技术，用于开发新的基于电化学的微流体流动装置，具有独特的功能，如容易切换流动方向，调节流动速度和流动模式，以及避免气泡的形成。然而，缺乏对所有涉及的力的详细描述和对受限几何形状中的流型的预测。除了氧化还原-MHD之外，氧化还原反应引起的密度梯度也起重要作用。在这些设备中的流动与小流体体积的主要特点是以下微珠运动的光学显微镜，通过粒子跟踪测速（PTV）或通过处理微珠图像的粒子图像测速（PIV）软件。这种方法在空间分辨率和维度上有局限性。在这里，我们使用荧光相关光谱（FCS）来定量和准确地测量在~5-50 μm/s范围内的基于氧化还原MHD的微流控设备的流速和模式，从其中获得3D流图，空间分辨率低至2 μm。2 μm空间分辨率的流速图显示了氧化还原-MHD过程中的详细流速分布，其中速度从电极上方线性增加，并在通道中心达到平台。通过结合FCS和视频显微镜（PTV和PIV处理方法），我们能够量化电极上方约10 μm/s的垂直流动，这是氧化还原反应引起的密度梯度的结果，并遵循对流模式。总体而言，结合氧化还原-MHD的FCS、PIV和PTV分析是一个强大的组合，可以更彻底地表征这些有前途的微流体装置中的潜在力。
Redox magnetohydrodynamics (MHD) is a promising technique for developing new electrochemical-based microfluidic flow devices with unique capabilities, such as easily switching flow direction, adjusting flow speeds and flow patterns as well as avoiding bubble formation. However, a detailed description of all the forces involved and predicting flow patterns in confined geometries is lacking. In addition to redox-MHD, density gradients caused by the redox reactions also play important roles. Flow in these devices with small fluid volumes has mainly been characterized by following microbead motion by optical microscopy either by particle tracking velocimetry (PTV) or by processing the microbead images by particle image velocimetry (PIV) software. This approach has limitations in spatial resolution and dimensionality. Here we use fluorescence correlation spectroscopy (FCS) to quantitatively and accurately measure flow speeds and patterns in the ~5-50 μm/s range in redox-MHD-based microfluidic devices, from which 3D flow maps are obtained with a spatial resolution down to 2 μm. The 2 μm spatial resolution flow speeds map revealed detailed flow profiles during redox-MHD in which the velocity increases linearly from above the electrode, and reaches a plateau across the center of the channel. By combining FCS and video-microscopy (with PTV and PIV processing approaches), we are able to quantify a vertical flow of ~10 μm/s above the electrodes as a result of density gradients caused by the redox reactions and follow convection flow patterns. Overall, combining FCS, PIV and PTV analysis of redox-MHD is a powerful combination to more thoroughly characterize the underlying forces in these promising microfluidic devices.
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影响因子：
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影响因子：
2.4
作者：
Qian S;Bau HH
通讯作者：
Bau HH