Department of Chemistry , University of Washington , Box 351700 , Seattle , Washington 98195 , United States.
University of Grenoble Alpes , F-38000 Grenoble , France.
Langmuir. 2018 May 8;34(18):5358-5366. doi: 10.1021/acs.langmuir.8b00380. Epub 2018 Apr 25.
Capillary open microsystems are attractive and increasingly used in biotechnology, biology, and diagnostics as they allow simple and reliable control of fluid flows. In contrast to closed microfluidic systems, however, two-phase capillary flows in open microfluidics have remained largely unexplored. In this work, we present the theoretical basis and experimental demonstration of a spontaneous capillary flow (SCF) of two-phase systems in open microchannels. Analytical results show that an immiscible plug placed in an open channel can never stop the SCF of a fluid in a uniform cross-section microchannel. Numerical investigations of the morphologies of immiscible plugs in a capillary flow reveal three different possible behaviors. Finally, the predicted behaviors of the plugs are demonstrated experimentally, revealing an effect of inertial forces on the plug behavior. A model for predicting plug behaviors in SCFs is proposed, enabling the design of open microfluidic droplet-based systems that are simple to fabricate and use. The open-channel approach to droplet-based microfluidics has the potential to enable applications in which each drop can be accessed at any time and any location with simple pipettes or other fluid dispensing systems.
在生物技术、生物学和诊断学中，毛细管开放式微系统因其能够简单可靠地控制流体流动而备受关注，并得到了越来越多的应用。然而，与封闭微流控系统不同，开放式微流控中的两相间的毛细管流动在很大程度上仍未得到探索。在这项工作中，我们提出了一种在开放式微通道中自发产生两相流的理论基础和实验演示。分析结果表明，放置在开放式通道中的不混溶塞永远无法阻止在具有均匀横截面的微通道中的流体的自发毛细管流动。对毛细管流动中不混溶塞的形态的数值研究揭示了三种可能的不同行为。最后，通过实验验证了塞子的预测行为，揭示了惯性力对塞子行为的影响。提出了一个用于预测自发毛细管流动中塞子行为的模型，该模型可用于设计简单易用的开放式微流控液滴系统。基于开放式通道的液滴微流控方法有可能实现这样的应用：通过简单的移液器或其他流体分配系统，能够在任何时间、任何位置访问每个液滴。
