Department of Chemical Engineering, Box 351750, University of Washington, Seattle, Washington 98195-1750, USA.
Anal Chem. 2012 Feb 21;84(4):1963-8. doi: 10.1021/ac203002z. Epub 2012 Feb 3.
Here we explore the role of microfabricated device geometry on frequency-dependent low Reynolds number steady streaming flow and particle trapping behavior. In our system, flow and particle trapping is induced near an obstruction or cavity located in an otherwise rectilinear oscillating flow of frequency ω and amplitude s in a fluid of kinematic viscosity ν. This work expands prior studies to characterize nine distinct obstruction/cavity geometries. The imaged microeddy flows show that the device geometry affects the eddy number, shape, structure, and strength. Comparison of measured particle trap locations with the computed eddy flow structure shows that particles trap closer to the wall than the eddy core. Trapping strength and location are controlled by the geometry and the oscillation frequency. In most cases, the trapping behavior is linearly proportional to the Stokes layer thickness, δ(AC) ~ O((ν/ω)(1/2)). We show that steady streaming in microfluidic eddies can be a flexible and versatile method for noncontact microparticle trapping, and hence we call this class of devices "hydrodynamic tweezers".
在这里，我们探讨了微制造器件几何形状对频率相关的低雷诺数定常流动和粒子捕获行为的影响。在我们的系统中，流动和粒子捕获是由位于障碍物或腔体内的流动引起的，该障碍物或腔体位于 otherwise rectilinear （其他直线的）振荡流中，该振荡流的频率为 ω，振幅为 s，在运动粘度为 ν 的流体中。这项工作扩展了先前的研究，以表征九种不同的障碍物/腔几何形状。所成像的微涡流流表明，器件几何形状会影响涡的数量、形状、结构和强度。将测量的粒子捕获位置与计算得到的涡流流结构进行比较表明，粒子比涡流核心更靠近壁面捕获。捕获强度和位置由几何形状和振荡频率控制。在大多数情况下，捕获行为与斯托克斯层厚度呈线性比例关系，δ(AC) ~ O((ν/ω)(1/2))。我们表明，微流道中的定常流动可以成为一种灵活且多功能的非接触式微粒子捕获方法，因此我们将这类器件称为“流体力学镊子”。
