制备复合液滴的微尺度流动方法

微尺度流动能够一步到位地制备不同结构和功能、尺寸在微米量级的复合液滴.文章回顾了几种常见的基于复合液滴的微尺度流动方法，包括同轴电雾化、复合流动聚焦、微流控芯片、玻璃微毛细管等，并对各种技术的原理和进展进行了简要概括和分析.在这类流动中，不同种类的流体在一定的几何结构通道或外力场作用下平稳地拉伸成微细射流并最终破碎成复合液滴.在同轴电雾化和复合流动聚焦技术中，从毛细管流出的流体能够形成稳定的锥-射流结构，当外力作用改变时能够形成不同的流动模式.在微流控芯片和玻璃微毛细管技术中，流体被约束在固定管道内，不同管道构型下能够形成不同的流动形态.这些方法都采用纯物理机理，过程稳定、易于操作，制备的复合液滴粒径可控，单分散性好，微观结构可设计，在科学研究和工程实际中具有重要的应用价值. 

Advances on Microfluidic Methods for Producing Compound Droplets

Microfluidics is advantageous for one-step fabricating compound droplets at micro scale with various structures and functions. This review surveys several microfluidic methods commonly used for producing compound droplets, including coaxial electrospray, co-flow focusing, lab on a chip and glass microcapillary. The principles and relevant progresses of these methods are briefly summarized and analyzed. In these flows, different types of fluids are stretched into microjets which eventually break up into compound droplets in channels with certain geometric structures or under external force fields. In coaxial electrospray and compound flow focusing techniques, the fluids flowing from the mouth of capillary are able to form steady cone-jet configurations, and different flow modes can be obtained as the external forces change. In lab on a chip and glass microcapillary devices, the fluids are often restricted in different channels, and the flow morphologies can be changed for different channel geometries. In these methods, the purely physical principles are employed, the processes are robust and easy to operate, and the compound droplets with controllable size, nice uniformity and designable microscopic structures can be fabricated. Therefore, they have significant applications in various science and technology areas.