Liquid control in microchannels is quite important in microfluidic devices used in, for example, lab-on-a-chip and point-of-care applications. Capillary microfluidics, being self-powered, is especially advantageous for use in passive devices, and has attracted significant attention. In this paper, capillary flows in rectangular microchannels with spacers are studied experimentally and theoretically; in particular, capillary flow synchronization (or waiting) behavior is identified and investigated. Based on changes of channel walls, two basic synchronization modes are proposed for flows isolated by spacers in a channel. Experimental results show that the velocities of faster capillary flows are reduced by the liquid pinning effect and that the time delay between two capillary flows is automatically balanced. The synchronization behavior of capillary flows is explained by analyzing the time delay, contact angle variation, and capillary forces. In addition, the quantity of liquid flowing out of the waiting channels is estimated and verified. Then a model for the change in contact angle during synchronization is derived and verified. Finally, we conceive a series of studies of the control of capillary flows for different spacer designs and conduct an experiment to study the dynamic behaviors of a number of capillary flows by adding many spacers in a microchannel. This study expands the applications of capillary microfluidics.

中文翻译：

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带有间隔器的矩形微通道中毛细管流的同步和控制。

在微流控设备中，微通道中的液体控制非常重要，例如，用于芯片实验室和即时医疗应用。自供电的毛细管微流体在无源设备中的使用特别有利，并引起了广泛的关注。本文通过实验和理论研究矩形矩形通道中的毛细管流动。特别是，识别并研究了毛细管流动同步（或等待）行为。基于通道壁的变化，为通道中的隔离物隔离的流提出了两种基本的同步模式。实验结果表明，液体钉扎效应降低了较快毛细管流动的速度，并且自动平衡了两个毛细管流动之间的时间延迟。通过分析时间延迟，接触角变化和毛细管力来解释毛细管流的同步行为。另外，估计和检验流出等待通道的液体量。然后，导出并验证了同步期间接触角变化的模型。最后，我们构想了一系列针对不同垫片设计的毛细管流控制的研究，并进行了一项实验，通过在微通道中添加许多垫片来研究许多毛细管流的动态行为。这项研究扩展了毛细管微流控技术的应用。然后，导出并验证了同步期间接触角变化的模型。最后，我们构想了一系列针对不同垫片设计的毛细管流控制的研究，并进行了一项实验，通过在微通道中添加许多垫片来研究许多毛细管流的动态行为。这项研究扩展了毛细管微流控技术的应用。然后，导出并验证了同步期间接触角变化的模型。最后，我们构想了一系列针对不同垫片设计的毛细管流控制的研究，并进行了一项实验，通过在微通道中添加许多垫片来研究许多毛细管流的动态行为。这项研究扩展了毛细管微流控技术的应用。