Measurement and mitigation of free convection in microfluidic gradient generators
Measurement and mitigation of free convection in microfluidic gradient generators
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DOI：
10.1039/c8lc00526e
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发表时间：
2018-11-21
期刊：
影响因子：
6.1
通讯作者：
Bishop, Kyle J. M.
中科院分区：
文献类型：
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作者：
Gu, Yang;Hegde, Varun;Bishop, Kyle J. M.
微流控梯度发生器被用来研究活细胞、脂泡和胶体颗粒对其局部化学环境的空间变化的响应。这种梯度驱动的运动通常是缓慢的(不到1米S(-1))，因此受到伴随着所施加的梯度的形成和维持的流体流动的影响或干扰。即使小心地消除外部流动，由于重力体力和扩散渗透表面力的组合，溶质梯度本身也可以驱动流体运动。在这里，我们开发了一种基于生物聚合物膜的原位形成的微流体梯度发生器，并对稳定的溶质梯度诱导的流体流动进行了量化。实验测得的流速分布与相关流体力学模型的解析近似所预测的流速分布定量吻合。我们讨论了梯度驱动流的速度如何依赖于系统参数，如梯度大小、流体粘度、通道尺寸和溶质类型。这些结果对于识别和缓解微流控梯度系统中的有害流动是有用的。
Microfluidic gradient generators are used to study the movement of living cells, lipid vesicles, and colloidal particles in response to spatial variations in their local chemical environment. Such gradient driven motions are often slow (less than 1 m s(-1)) and therefore influenced or disrupted by fluid flows accompanying the formation and maintenance of the applied gradient. Even when external flows are carefully eliminated, the solute gradient itself can drive fluid motions due to combinations of gravitational body forces and diffusioosmotic surface forces. Here, we develop a microfluid gradient generator based on the in situ formation of biopolymer membranes and quantify the fluid flows induced by steady solute gradients. The measured velocity profiles agree quantitatively with those predicted by analytical approximations of relevant hydrodynamic models. We discuss how the speed of gradient-driven flows depends on system parameters such as the gradient magnitude, the fluid viscosity, the channel dimensions, and the solute type. These results are useful in identifying and mitigating undesired flows within microfluidic gradient systems.