Zhang Longxiang, Liu Zhaomiao, Pang Yan, Wang Xiang, Li Mengqi, Ren Yanlin
College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology Beijing 100124 China
RSC Adv. 2018 Feb 27;8(16):8787-8794. doi: 10.1039/c7ra13507f. eCollection 2018 Feb 23.
Trapping a train of moving droplets into preset positions within a microfluidic device facilitates the long-term observation of biochemical reactions inside the droplets. In this paper, a new bubble-guided trapping method, which can remarkably improve the limited narrow two-phase flow rate range of uniform trapping, was proposed by taking advantage of the unique physical property that bubbles do not coalescence with two-phase fluids and the hydrodynamic characteristic of large flow resistance of bubbles. The flow behaviors of bubble-free and bubble-guided droplet trains were compared and analyzed under the same two-phase flow rates. The experimental results show that the droplets trapped by bubble-free guided trapping exhibit the four trapping modes of sequentially uniform trapping, non-uniform trapping induced by break-up and collision, and failed trapping due to squeezing through, and the droplets exhibit the desired uniform trapping in a relatively small two-phase flow rate range. Compared with bubble-free guided droplets, bubble-guided droplets also show four trapping modes. However, the two-phase flow rate range in which uniform trapping occurs is increased significantly and the uniformity of the trapped droplet array is improved. This investigation is beneficial to enhance the applicability of microfluidic chips for storing droplets in a passive way.
将一串移动的液滴捕获到微流控装置内的预设位置，有助于对液滴内部的生化反应进行长期观察。本文利用气泡不与两相流体合并的独特物理性质以及气泡大流动阻力的流体动力学特性，提出了一种新的气泡引导捕获方法，该方法可显著改善均匀捕获有限的狭窄两相流速范围。在相同的两相流速下，对无气泡和气泡引导的液滴串的流动行为进行了比较和分析。实验结果表明，无气泡引导捕获捕获的液滴呈现出顺序均匀捕获、破碎和碰撞诱导的非均匀捕获以及挤压通过导致的捕获失败这四种捕获模式，并且液滴在相对较小的两相流速范围内呈现出所需的均匀捕获。与无气泡引导的液滴相比，气泡引导的液滴也呈现出四种捕获模式。然而，发生均匀捕获的两相流速范围显著增加，并且捕获的液滴阵列的均匀性得到改善。这项研究有利于提高微流控芯片以被动方式存储液滴的适用性。
