Microscale, scanning defocusing volumetric particle-tracking velocimetry
Microscale, scanning defocusing volumetric particle-tracking velocimetry
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DOI：
10.1007/s00348-019-2731-4
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发表时间：
2019-06-01
影响因子：
2.4
通讯作者：
Vlachos, Pavlos P.
中科院分区：
文献类型：
--
作者：
Guo, Tianqi;Ardekani, Arezoo M.;Vlachos, Pavlos P.
提出了一种新的用于微流控系统的散焦粒子跟踪测速方法。该方法提供三维3分量（3D 3C）流测量，并且不需要额外的校准程序来获得颗粒面外位置与其直径/强度之间的关系。微流体装置安装在纳米定位压电台上，该压电台在平面外方向上周期性地扫描。一个高速摄像机同步的阶段，捕捉过采样的二维显微镜图像在不同的平面外的位置。通过堆叠这些2D图像形成3D强度体积。通过3D Hessian滤波器从强度体积中识别血流示踪剂，并通过侵蚀膨胀动态阈值分割进行分割。每个识别粒子的散焦强度模型的拟合给出了粒子图像测速和广义多参数PTV的混合算法中使用的参数。人工图像数据，通过多孔介质的流动的直接数值模拟产生的，用于误差分析。当与经典的最近邻跟踪相比，我们的方法显示出跟踪可靠性提高了2.5- 12%，种子密度高达1.6e-3粒子每体素。平均误差和均方根误差分别提高了80-95%和49- 74%。通过测量折射率匹配的随机填充玻璃珠通道的稳态流动，给出了微流控器件的应用。所提出的方法将作为一个强大的工具，探测在微流体与复杂的几何形状的流动物理。[图形]。
We present a novel defocusing particle tracking velocimetry (PTV) method for micro-fluidic systems. This method delivers 3-dimensional 3-component (3D3C) flow measurements, and does not require an additional calibration procedure to obtain the relationship between particle out-of-plane position and its diameter/intensity. A micro-fluidic device is mounted on a nano-positioning piezo stage that sweeps periodically in the out-of-plane direction. A high-speed camera is synchronized with the stage to capture oversampled two-dimensional microscopy images at different out-of-plane positions. 3D intensity volume is formed by stacking those 2D images. Flow tracers are identified from the intensity volume by a 3D Hessian filter, and segmented by erosion-dilation dynamic thresholding. Fitting of each identified-particle to a defocusing intensity model gives the parameters used in the hybrid algorithm of particle image velocimetry and a generalized multi-parametric PTV. Artificial image data, generated from direct numerical simulations of flow through porous media, are used for error analysis. When compared with classic nearest neighbor tracking our method shows improvements on tracking reliability by 2.5-12%, with seeding density as high as 1.6e-3 particles per voxel. Both mean and rms errors are improved by 80-95% and 49-74%, respectively. An application to micro-fluidic devices is presented by measuring the steady-state flow through a refractive-index-matched randomly-packed glass bead channel. The presented method will serve as a powerful tool for probing flow physics in micro-fluidics with complex geometries.[GRAPHICS].