IEEE Trans Biomed Circuits Syst. 2017 Dec;11(6):1406-1412. doi: 10.1109/TBCAS.2017.2722012. Epub 2017 Aug 14.
In this paper, we proposed a microparticle manipulation approach, by which particles are able to be guided to different equilibrium positions through modulating the Reynolds number. In the microchannel with arc-shaped groove arrays, secondary flow vortex arisen due to the pressure gradient varies in the aspects of both magnitude and shape with the increase of Reynolds number. And the variation of secondary flow vortex brings about different focusing modes of microparticles in the microchannel. We investigated the focusing phenomenon experimentally and analyzed the mechanism through numerical simulations. At a high Reynolds number (Re = 127.27), the geometry-induced secondary flow rotates constantly along a direction, and most particles are guided to the equilibrium position near one side of the microchannel. However, at a low Reynolds number (Re = 2.39), the shapes of geometry-induced secondary flow vortices are obviously different, forming a variant Dean-like vortex that consists of two asymmetric counter-rotating streams in cross sections of the straight channel. Because of the periodical effects, suspended particles are concentrated at another equilibrium position on the opposite side of the microchannel. Meanwhile, the effects of particle size influence both the focusing position and quality in regimes.
本文提出了一种基于微粒子操控的方法，通过调节雷诺数使粒子能够被引导至不同的平衡位置。在带有弧形凹槽阵列的微通道中，由于压力梯度的变化，二次流涡旋在大小和形状两方面都随雷诺数的增加而发生变化。二次流涡旋的变化导致微通道中微粒子的不同聚焦模式。我们通过实验研究了聚焦现象，并通过数值模拟分析了其机制。在高雷诺数（Re = 127.27）下，几何诱导的二次流沿一个方向不断旋转，大部分粒子被引导到微通道一侧的平衡位置。然而，在低雷诺数（Re = 2.39）下，几何诱导的二次流涡的形状明显不同，形成了一种变体的 Dean 型涡旋，在直通道的横截面上由两个不对称的反向旋转流组成。由于周期性的影响，悬浮颗粒集中在微通道另一侧的另一个平衡位置。同时，颗粒尺寸的影响会影响到各个区域的聚焦位置和质量。
