Mechanical Engineering Department, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands.
Institute of Complex Molecular Systems, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands.
Lab Chip. 2023 Mar 14;23(6):1524-1530. doi: 10.1039/d2lc01168a.
Various types of passive and active micromixers have been successfully developed to address the problem of mixing in microfluidic devices. However, many applications do not need fluids to be mixed at all times, or indeed require mixing to be turned on and off at will. Achieving such on-demand mixing is not feasible for passive mixers, particularly when the flow rate cannot be used as a control parameter. On the other hand, active mixers are usually not designed to be able to turn mixing off completely, and they often have complicated fabrication processes and special operation requirements, limiting the range of applications. In this work, we demonstrate an on-demand micromixer based on the actuation of magnetic microwalls. These are made by replica micromoulding and can be easily integrated within commercial microfluidic devices, such as the ibidi® 3-in-1 μ-Slide. Using a simple magnet, the microwalls can be actuated between a fully upright 'on' state, which turns on mixing by creating a meandering path in the main channel, and a fully collapsed 'off' state, which completely turns off mixing by opening up the channel leaving it unobstructed. Besides the increase in path length when the microwalls are activated, inertia effects also play a significant role for mixing due to the tight bends in the meandering flow path. We quantify the mixing effect using coloured fluids of different viscosities and at different flow rates, and we show that the microwalls can effectively enhance mixing across a wide range of operational conditions.
已经成功开发出各种类型的被动和主动微混合器来解决微流控设备中的混合问题。然而，许多应用并不需要始终混合流体，或者实际上需要随意打开和关闭混合。对于被动混合器来说，实现这种按需混合是不可行的，特别是当流速不能用作控制参数时。另一方面，主动混合器通常不是为了能够完全关闭混合而设计的，而且它们通常具有复杂的制造工艺和特殊的操作要求，限制了应用范围。在这项工作中，我们展示了一种基于磁微墙致动的按需微混合器。这些微墙是通过复制微成型制成的，可以很容易地集成在商业微流控设备中，例如 ibidi® 3-in-1 μ-Slide。使用简单的磁铁，微墙可以在完全垂直的“开”状态和完全折叠的“关”状态之间进行致动，在“开”状态下，微墙会在主通道中产生蜿蜒的路径，从而打开混合，在“关”状态下，微墙会完全打开通道，使其畅通无阻，从而完全关闭混合。除了微墙激活时路径长度的增加之外，由于蜿蜒流道的紧密弯曲，惯性效应也对混合产生了重大影响。我们使用不同粘度和不同流速的有色流体来量化混合效果，并表明微墙可以在广泛的操作条件下有效地增强混合。
