Droplets are excellent platforms for compartmentalization of many processes such as chemical reactions, liquid–liquid extraction, and biological or chemical analyses. Accurately controlling and optimizing the composition of these droplets is of high importance to maximize their functionality. In this work, the formation of multicomponent droplets with controllable composition by employing a continuous flow-in setup is demonstrated. Multiple streams of different oil solutions are introduced and mixed in a passive flow mixer and the outcoming mixture is subsequently fed into a flow chamber to form surface nanodroplets by solvent exchange. This method is time-effective, enabling programmable continuous processes for droplet formation and surface cleaning. The surface nanodroplets are formed within 2.5 min in one cycle, and the droplet formation is reliable with similar size distribution over multiple cycles. The composition of the resulting surface nanodroplet can be tuned at will simply by controlling the flow rate ratios of each stream of the oil solution. Using fluorescence imaging, it is shown that the composition of the binary surface nanodroplets agrees well with theoretical values predicted using the phase diagram.

中文翻译：

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在连续流入系统中调整多组分表面纳米液滴的组成

液滴是许多过程（例如化学反应、液-液萃取以及生物或化学分析）的划分的绝佳平台。准确控制和优化这些液滴的组成对于最大化其功能非常重要。在这项工作中，演示了通过采用连续流入设置形成具有可控成分的多组分液滴。在被动流动混合器中引入和混合多股不同的油溶液，随后将输出的混合物送入流动室，通过溶剂交换形成表面纳米液滴。这种方法省时，可实现液滴形成和表面清洁的可编程连续过程。表面纳米液滴在一个周期内在 2.5 分钟内形成，并且液滴形成是可靠的，在多个循环中具有相似的尺寸分布。可以简单地通过控制油溶液各流的流速比来随意调整所得表面纳米液滴的组成。使用荧光成像，表明二元表面纳米液滴的组成与使用相图预测的理论值非常吻合。