Jia Yankai, Ren Yukun, Hou Likai, Liu Weiyu, Deng Xiaokang, Jiang Hongyuan
School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001, China.
Small. 2017 Dec;13(46). doi: 10.1002/smll.201702188. Epub 2017 Oct 16.
Advances in microfluidic emulsification have enabled the generation of exquisite multiple-core droplets, which are promising structures to accommodate microreactions. An essential requirement for conducting reactions is the sequential coalescence of the multiple cores encapsulated within these droplets, therefore, mixing the reagents together in a controlled sequence. Here, a microfluidic approach is reported for the conduction of two-step microreactions by electrically fusing three cores inside double-emulsion droplets. Using a microcapillary glass device, monodisperse water-in-oil-in-water droplets are fabricated with three compartmented reagents encapsulated inside. An AC electric field is then applied through a polydimethylsiloxane chip to trigger the sequential mixing of the reagents, where the precise sequence is guaranteed by the discrepancy of the volume or conductivity of the inner cores. A two-step reaction in each droplet is ensured by two times of core coalescence, which totally takes 20-40 s depending on varying conditions. The optimal parameters of the AC signal for the sequential fusion of the inner droplets are identified. Moreover, the capability of this technique is demonstrated by conducting an enzyme-catalyzed reaction used for glucose detection with the double-emulsion droplets. This technique should benefit a wide range of applications that require multistep reactions in micrometer scale.
微流控乳化技术的进展使得生成精美的多核液滴成为可能，这些液滴是容纳微反应的有前景的结构。进行反应的一个基本要求是这些液滴内封装的多个核依次合并，从而以可控的顺序将试剂混合在一起。在此，报道了一种微流控方法，用于通过电融合双乳液滴内的三个核来进行两步微反应。使用微毛细管玻璃装置，制备了单分散的水包油包水液滴，内部封装有三种分隔的试剂。然后通过聚二甲基硅氧烷芯片施加交流电场，以触发试剂的顺序混合，其中精确的顺序由内核体积或电导率的差异保证。每个液滴中的两步反应通过两次核合并来确保，这总共需要20 - 40秒，具体取决于不同条件。确定了用于内部液滴顺序融合的交流信号的最佳参数。此外，通过用双乳液滴进行用于葡萄糖检测的酶催化反应，证明了该技术的能力。该技术应有利于广泛的需要在微米尺度上进行多步反应的应用。
