Fluid Dynamics Group, CSIRO Materials Science and Engineering, Melbourne, Australia.
Biotechniques. 2009 Oct;47(4):827-34. doi: 10.2144/000113242.
Mixing fluids for biochemical assays is problematic when volumes are very small (on the order of the 10 microL typical of single drops), which has inspired the development of many micromixing devices. In this paper, we show that micromixing is possible in the simple open wells of standard laboratory consumables using appropriate acoustic frequencies that can be applied using cheap, conventional audio components. Earlier work has shown that the phenomenon of acoustic microstreaming can mix fluids, provided that bubbles are introduced into a specially designed microchamber or that high-frequency surface acoustic wave devices are constructed. We demonstrate a key simplification: acoustic micromixing at audio frequencies by ensuring the system has a liquid-air interface with a small radius of curvature. The meniscus of a drop in a small well provided an appropriately small radius, and so an introduced bubble was not necessary. Microstreaming showed improvement over diffusion-based mixing by 1-2 orders of magnitude. Furthermore, significant improvements are attainable through the utilization of chaotic mixing principles, whereby alternating fluid flow patterns are created by applying, in sequence, two different acoustic frequencies to a drop of liquid in an open well.
在体积非常小（通常为单个液滴的 10 微升）的情况下，混合生物化学分析用的液体是有问题的，这激发了许多微混合设备的发展。在本文中，我们展示了使用适当的声波频率可以在标准实验室耗材的简单开放式井中实现微混合，这些频率可以使用廉价的传统音频组件来实现。早期的工作表明，只要在专门设计的微腔中引入气泡，或者构建高频表面声波设备，声致微流动现象就可以混合液体。我们证明了一个关键的简化方案：通过确保系统具有小曲率半径的液-气界面，在音频频率下进行声学微混合。小井中的液滴的弯月面提供了适当小的半径，因此不需要引入气泡。与基于扩散的混合相比，微流动显示出 1-2 个数量级的改善。此外，通过利用混沌混合原理可以实现显著的改进，通过顺序地将两种不同的声波频率施加到开放式井中的液滴上，可以创建交替的流体流动模式。
