By utilizing water transport phenomena between two different water-in-oil (W/O) emulsion droplets through continuous oil phase, we developed a novel method of aqueous two-phase system (ATPS) formation in small droplets prepared by Shirasu porous glass (SPG) membrane emulsification technique. When we mixed W/O emulsion droplets containing poly(ethylene glycol) (PEG) and dextran (DEX) at concentrations below the threshold of the phase separation, with droplets containing other solutes at high concentrations, water extraction from the droplets containing PEG and DEX to those containing the other solutes occurred, owing to the osmotic pressure difference. This effect increased the concentrations of PEG and DEX in the droplets above the phase separation threshold. We demonstrated the feasibility of the preparation method by varying the pore sizes of the SPG membranes, the solutes, and their concentrations. Only when the concentration of the solute was high enough to extract sufficient amounts of water did the homogeneous disperse phase consisting of PEG and DEX in droplets turn into a PEG-rich phase and DEX-rich phase, showing ATPS. This result was irrespective of the solute itself and pore size of the SPG membrane. In particular, we successfully demonstrated monodisperse ATPS droplets with diameters of approximately 10 μm under a certain condition.

中文翻译：

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Shirasu多孔玻璃膜乳化后水萃取在小液滴中形成两相水系统

通过利用连续油相在两个不同的油包水（W / O）乳剂小滴之间的水传输现象，我们开发了一种由Shirasu多孔玻璃（SPG）制备的在小液滴中形成水两相系统（ATPS）的新方法）膜乳化技术。当我们将浓度低于相分离阈值的W / O乳状液小滴包含聚（乙二醇）（PEG）和右旋糖酐（DEX）的液滴与高浓度包含其他溶质的液滴混合时，将从包含PEG和DEX的液滴中提取水由于渗透压差，含有其他溶质的那些发生了。这种作用使液滴中PEG和DEX的浓度增加到相分离阈值以上。我们通过改变SPG膜的孔径，溶质及其浓度证明了制备方法的可行性。只有当溶质的浓度足够高以提取足够量的水时，由液滴中的PEG和DEX组成的均匀分散相才变成富含PEG的相和富含DEX的相，显示出ATPS。该结果与溶质本身和SPG膜的孔径无关。特别是，我们成功地证明了在特定条件下直径约10μm的单分散ATPS液滴。只有当溶质的浓度足够高以提取足够量的水时，由液滴中的PEG和DEX组成的均匀分散相才变成富含PEG的相和富含DEX的相，显示出ATPS。该结果与溶质本身和SPG膜的孔径无关。特别是，我们成功地证明了在特定条件下直径约10μm的单分散ATPS液滴。只有当溶质的浓度足够高以提取足够量的水时，由液滴中的PEG和DEX组成的均匀分散相才变成富含PEG的相和富含DEX的相，显示出ATPS。该结果与溶质本身和SPG膜的孔径无关。特别是，我们成功地证明了在特定条件下直径约10μm的单分散ATPS液滴。