Droplet microfluidics are characterized by the generation and manipulation of discrete volumes of solutions, generated with the use of immiscible phases. Those droplets can then be controlled, transported, analyzed or their content modified. In this wide droplet microfluidic toolbox, no means are available to generate, in a controlled manner, droplets co-encapsulating to aqueous phases. Indeed, current methods rely on random co-encapsulation of two aqueous phases during droplet generation or the merging of two random droplets containing different aqueous phases. In this study, we present a novel droplet microfluidic device to reliably and efficiently co-encapsulate two different aqueous phases in micro-droplets. In order to achieve this, we combined existing droplet microfluidic modules in a novel way. The different aqueous phases are individually encapsulated in droplets of different sizes. Those droplet populations are then filtered in order to position each droplet type towards its adequate trapping compartment in traps of a floating trap array. Single droplets, each containing a different aqueous phase, are thus paired and then merged. This pairing at high efficiency is achieved thanks to a unique combination of floating trap arrays, a droplet railing system and a droplet size-based filtering mechanism. The microfluidic chip design presented here provides a filtering threshold with droplets larger than 35 μm (big droplets) being deviated to the lower rail while droplets smaller than 20 μm (small droplets) remain on the upper rail. The effects of the rail height and the distance between the two (upper and lower) rails were investigated. The optimal trap dimensions provide a trapping efficiency of 100% for small and big droplets with a limited double trapping (both compartments of the traps filled with the same droplet type) of 5%. The use of electrocoalescence enables the generation of a droplet while co-encapsulating two aqueous phases. Using the presented microfluidic device libraries of 300 droplets, dual aqueous content can be generated in less than 30 min.

中文翻译：

---

通过结合液滴栏杆和浮动捕集器阵列进行液滴配对的微流体装置


液滴微流体的特点是通过使用不混溶相生成和操纵离散体积的溶液。然后可以控制、运输、分析这些液滴或修改其内容。在这种宽液滴微流体工具箱中，没有任何方法可以以受控方式生成共封装到水相的液滴。事实上，当前的方法依赖于液滴生成过程中两个水相的随机共封装或包含不同水相的两个随机液滴的合并。在这项研究中，我们提出了一种新型的液滴微流体装置，可以可靠且有效地将两种不同的水相共同封装在微滴中。为了实现这一目标，我们以一种新颖的方式组合了现有的液滴微流体模块。不同的水相被单独封装在不同尺寸的液滴中。然后过滤这些液滴群，以便将每种液滴类型定位在浮动捕获阵列的捕获器中朝向其适当的捕获隔室。每个含有不同水相的单个液滴因此配对然后合并。这种高效配对的实现得益于浮动陷阱阵列、液滴栏系统和基于液滴尺寸的过滤机制的独特组合。这里介绍的微流控芯片设计提供了一个过滤阈值，大于 35 μm 的液滴（大液滴）被偏转到下导轨，而小于 20 μm 的液滴（小液滴）保留在上导轨上。研究了轨道高度和两根（上、下）轨道之间距离的影响。 最佳捕集器尺寸为小液滴和大液滴提供了 100% 的捕集效率，并且有限的双捕集（捕集器的两个隔室都填充了相同的液滴类型）为 5%。使用电聚结可以在共封装两个水相的同时生成液滴。使用所提供的 300 个液滴的微流体装置库，可以在不到 30 分钟的时间内生成双水内容物。