Kim Uihwan, Kwon Joo-Yong, Kim Taehoon, Cho Younghak
Department of Mechanical Design and Robot Engineering, Seoul National University of Science & Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea.
Department of Mechanical System Design Engineering, Seoul National University of Science & Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea.
Micromachines (Basel). 2022 Jan 20;13(2):151. doi: 10.3390/mi13020151.
Recently, studies on particle behavior under Newtonian and non-Newtonian fluids in microchannel have attracted considerable attention because particles and cells of interest can be manipulated and separated from biological samples without any external force. In this paper, two kinds of microchannels with non-rectangular cross-section were fabricated using basic MEMS processes (photolithography, reactive ion etching and anisotropy wet etching), plasma bonding and self-alignment between two PDMS structures. They were used to achieve the experiments for inertial and elasto-inertial particle focusing under Newtonian and non-Newtonian fluids. The particle behavior was compared and investigated for different flow rates and particle size in the microchannel with rhombic and equilateral hexagonal cross section. We also investigated the influence of Newtonian fluid and viscoelastic fluid on particle migration in both microchannels through the numerical simulation. The experimental results showed the multi-line particle focusing in Newtonian fluid over a wide range of flow rates, but the single-line particle focusing was formed in the centerline under non-Newtonian fluid. The tighter particle focusing appeared under non-Newtonian fluid in the microchannel with equilateral hexagonal cross-section than in the microchannel with rhombic cross section because of the effect of an obtuse angle. It revealed that particles suspended in the channel are likely to drift toward a channel center due to a negative net elasto-inertial force throughout the cross-sectional area. Simulation results support the present experimental observation that the viscoelastic fluid in the microchannel with rhombic and equilateral hexagonal cross-section significantly influences on the particle migration toward the channel center owing to coupled effect of inertia and elasticity.
最近，微通道中牛顿流体和非牛顿流体作用下的颗粒行为研究备受关注，因为感兴趣的颗粒和细胞无需任何外力即可从生物样品中得到操控和分离。本文利用基本的微机电系统工艺（光刻、反应离子刻蚀和各向异性湿法刻蚀）、等离子体键合以及两个聚二甲基硅氧烷（PDMS）结构之间的自对准，制备了两种非矩形横截面的微通道。它们被用于开展牛顿流体和非牛顿流体作用下的惯性和弹性-惯性颗粒聚焦实验。针对具有菱形和等边六边形横截面的微通道，比较并研究了不同流速和颗粒尺寸下的颗粒行为。我们还通过数值模拟研究了牛顿流体和粘弹性流体对两种微通道中颗粒迁移的影响。实验结果表明，在较宽的流速范围内，牛顿流体中会出现多线颗粒聚焦，但在非牛顿流体中，颗粒会在中心线处形成单线聚焦。由于钝角的影响，等边六边形横截面微通道中的非牛顿流体比菱形横截面微通道中的非牛顿流体产生更紧密的颗粒聚焦。结果表明，由于整个横截面积上的负净弹性-惯性力，通道中悬浮的颗粒可能会向通道中心漂移。模拟结果支持了目前的实验观察，即菱形和等边六边形横截面微通道中的粘弹性流体由于惯性和弹性的耦合作用，对颗粒向通道中心的迁移有显著影响。
