Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China.
Lab Chip. 2021 Jul 13;21(14):2684-2690. doi: 10.1039/d1lc00351h.
An aqueous two-phase system (ATPS) is considered as a promising candidate for biological applications due to its excellent permeability, selective separation, rapid mass transfer and all-biocompatible nature. However, it remains difficult to generate ATPS emulsions with controllable and prolonged stability due to ultra-low interfacial tension. Here, we present a transient double emulsion (TDE) technique to address this challenge. The method involves two steps: (i) water-in-oil-in-water (W1/O/W2) transient double emulsion droplets are first produced with droplet microfluidics by introducing an additional middle oil phase, and (ii) the W1/O/W2 droplets dewet into oil-in-water and ATPS droplets in a controllable manner. Using the TDE method, both dextran-in-polyethylene glycol (PEG) and PEG-in-dextran ATPS droplets can be generated with high uniformity (coefficient of variation (CV) ranging from 0.66% to 2.55%), a wide range of droplet sizes (∼100 to 250 μm in radius), and tunability in the generation frequency (∼4 to 170 Hz). Tuning the oil viscosity controls the destabilization time for on-demand dewetting and releasing of aqueous core droplets. The stability of ATPS droplets is significantly improved by storing aqueous droplets in double emulsion vessels, which would benefit various applications, such as small molecule encapsulation.
双水相系统（ATPS）因其具有优异的渗透性、选择性分离、快速传质和全生物相容性而被认为是生物应用的有前途的候选物。然而，由于超低的界面张力，仍然难以生成具有可控和持久稳定性的 ATPS 乳液。在这里，我们提出了一种瞬态双重乳液（TDE）技术来解决这个挑战。该方法包括两个步骤：（i）通过引入额外的中间油相，首先使用液滴微流控技术产生油包水包油（W1/O/W2）瞬态双重乳液液滴，（ii）W1/O/W2 液滴以可控的方式去湿为油包水和 ATPS 液滴。使用 TDE 方法，可以生成具有高均匀性（变化系数（CV）范围为 0.66%至 2.55%）、广泛的液滴尺寸（半径约为 100 至 250 μm）和可调谐生成频率（约 4 至 170 Hz）的葡聚糖-聚乙二醇（PEG）和 PEG-葡聚糖 ATPS 液滴。调节油的粘度可以控制按需去湿和释放水芯液滴的失稳时间。通过将水相液滴储存在双重乳液容器中，可以显著提高 ATPS 液滴的稳定性，这将有利于各种应用，如小分子封装。
