Self-assembly of coated microdroplets at the sudden expansion of a microchannel
Self-assembly of coated microdroplets at the sudden expansion of a microchannel
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DOI：
10.1007/s10404-021-02424-z
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发表时间：
2021-03-01
影响因子：
2.8
通讯作者：
Juel, Anne
中科院分区：
文献类型：
--
作者：
Schirrmann, Kerstin;Caceres-Aravena, Gabriel;Juel, Anne
我们报告的自组装成定期集群的微流体通道的突然扩张的涂层液滴的观察。在通道扩张的上游产生由一列规则的涂覆微滴组成的双重乳液，使得液滴间距离、液滴长度、速度和涂层厚度可以通过施加不同的入口压力而变化，尽管不是独立的。只要扩大的通道保持足够的限制，以防止在双文件中的传播，液滴可以组装成规则的线性集群在扩展顺序。液滴通过它们的涂膜与前面的那一组结合而加入一个集群。当液滴在膨胀时彼此接近到临界距离内时，这种聚结发生，这是通过列车内的流体动力学相互作用实现的。获得包括有限数量的液滴的簇，因为在聚结期间液滴组件的重新配置增加了到下一个液滴的距离。减小液滴间距离会将簇大小增加到最大值，超过该最大值会形成连续簇。在一个简单的模型中形式化这些观察结果表明，任何大小的集群都是可能的，但它们发生的参数值范围越来越窄。我们的实验观察表明，背景实验波动限制在实践中的最大离散集群的大小。这种自组装方法提供了一个强大的替代流动聚焦封装在一个单一的涂层膜和潜在的多个核心，建立更复杂的胶体构建块通过解除限制的集群。
We report observations of the self-assembly of coated droplets into regular clusters at the sudden expansion of a microfluidic channel. A double emulsion consisting of a regular train of coated microdroplets was created upstream of the channel expansion, so that the inter-drop distance, droplet length, velocity and coating thickness could be varied by imposing different inlet pressures, albeit not independently. Provided that the enlarged channel remains sufficiently confined to prohibit propagation in double file, droplets can assemble sequentially into regular linear clusters at the expansion. Droplets join a cluster via the coalescence of their coating film with that of the group ahead. This coalescence occurs when the droplets approach each other to within a critical distance at the expansion, enabled by hydrodynamic interactions within the train. Clusters comprising a finite number of droplets are obtained because reconfiguration of the droplet assembly during coalescence increases the distance to the following droplet. Decreasing the inter-drop distance increases the cluster size up to a maximum value beyond which continuous clusters form. Formalising these observations in a simple model reveals that clusters of any size are possible but that they occur for increasingly narrow ranges of parameter values. Our experimental observations suggests that background experimental fluctuations limit the maximum discrete cluster size in practice. This method of self-assembly offers a robust alternative to flow focusing for encapsulating multiple cores in a single coating film and the potential to build more complex colloidal building blocks by de-confining the clusters.