Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
Anal Chem. 2017 Apr 4;89(7):4091-4099. doi: 10.1021/acs.analchem.6b05041. Epub 2017 Mar 13.
By rapidly creating libraries of thousands of unique, miniaturized reactors, droplet microfluidics provides a powerful method for automating high-throughput chemical analysis. In order to engineer in-droplet assays, microfluidic devices must add reagents into droplets, remove fluid from droplets, and perform other necessary operations, each typically provided by a unique, specialized geometry. Unfortunately, modifying device performance or changing operations usually requires re-engineering the device among these specialized geometries, a time-consuming and costly process when optimizing in-droplet assays. To address this challenge in implementing droplet chemistry, we have developed the "K-channel," which couples a cross-channel flow to the segmented droplet flow to enable a range of operations on passing droplets. K-channels perform reagent injection (0-100% of droplet volume), fluid extraction (0-50% of droplet volume), and droplet splitting (1:1-1:5 daughter droplet ratio). Instead of modifying device dimensions or channel configuration, adjusting external conditions, such as applied pressure and electric field, selects the K-channel process and tunes its magnitude. Finally, interfacing a device-embedded magnet allows selective capture of 96% of droplet-encapsulated superparamagnetic beads during 1:1 droplet splitting events at ∼400 Hz. Addition of a second K-channel for injection (after the droplet splitting K-channel) enables integrated washing of magnetic beads within rapidly moving droplets. Ultimately, the K-channel provides an exciting opportunity to perform many useful droplet operations across a range of magnitudes without requiring architectural modifications. Therefore, we envision the K-channel as a versatile, easy to use microfluidic component enabling diverse, in-droplet (bio)chemical manipulations.
通过快速创建数千个独特的微型化反应器库，液滴微流控技术为自动化高通量化学分析提供了一种强大的方法。为了在液滴内进行工程设计，微流控设备必须向液滴中添加试剂、从液滴中去除流体并执行其他必要的操作，这些操作通常需要独特的、专门的几何形状来完成。不幸的是，修改设备性能或更改操作通常需要在这些专门的几何形状之间重新设计设备，这在优化液滴内分析时是一个耗时且昂贵的过程。为了解决在实施液滴化学方面的这一挑战，我们开发了“K 通道”，它将交叉通道流与分段液滴流耦合在一起，从而能够对通过的液滴进行一系列操作。K 通道执行试剂注入（0-100%的液滴体积）、流体提取（0-50%的液滴体积）和液滴分裂（1:1-1:5 子液滴比）。K 通道不是通过修改设备尺寸或通道配置，而是通过调整外部条件（如施加的压力和电场）来选择 K 通道过程并调整其幅度。最后，在设备中嵌入磁铁可以在 400Hz 左右的 1:1 液滴分裂事件中选择性捕获 96%包裹在液滴中的超顺磁珠。添加第二个用于注入的 K 通道（在液滴分裂 K 通道之后）可以在快速移动的液滴中集成磁珠洗涤。最终，K 通道提供了一个令人兴奋的机会，可以在不要求结构修改的情况下，在广泛的幅度内执行许多有用的液滴操作。因此，我们设想 K 通道是一种通用、易于使用的微流控组件，能够实现多样化的液滴（生物）化学操作。
