Xu Xiaonan, Yuan Haojun, Song Ruyuan, Yu Miao, Chung Ho Yin, Hou Youmin, Shang Yuhe, Zhou Hongbo, Yao Shuhuai
Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China.
State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai, China.
Biomicrofluidics. 2018 Jan 2;12(1):014103. doi: 10.1063/1.5011240. eCollection 2018 Jan.
Droplet microfluidics, which involves micrometer-sized emulsion droplets on a microfabricated platform, has been demonstrated as a unique system for many biological and chemical applications. Robust and scalable generation of monodisperse droplets at high throughput is of fundamental importance for droplet microfluidics. Classic designs for droplet generation employ shear fluid dynamics to induce the breakup of droplets in a two-phase flow and the droplet size is sensitive to flow rate fluctuations, often resulting in polydispersity. In this paper, we show spontaneous emulsification by a high aspect ratio (>3.5) rectangular nozzle structure. Due to the confinement and abrupt change of the structure, a Laplace pressure difference is generated between the dispersed and continuous phases, and causes the thread thinning and droplet pinch-off without the need to precisely control external flow conditions. A high-throughput droplet generator was developed by parallelization of a massive number of the basic structures. This device enabled facile and rapid partition of aqueous samples into millions of uniform picolitre droplets in oil. Using this device, on-chip droplet-based digital polymerase chain reaction (PCR) was performed for absolute quantification of rare genes with a wide dynamic range.
液滴微流控技术涉及在微制造平台上的微米级乳液液滴，已被证明是一种适用于许多生物和化学应用的独特系统。在高通量下稳健且可扩展地生成单分散液滴对于液滴微流控技术至关重要。经典的液滴生成设计采用剪切流体动力学来诱导两相流中液滴的破裂，并且液滴尺寸对流速波动敏感，常常导致多分散性。在本文中，我们展示了通过高纵横比（>3.5）矩形喷嘴结构实现的自发乳化。由于结构的限制和突变，在分散相和连续相之间产生了拉普拉斯压差，导致液柱变细和液滴 pinch-off，而无需精确控制外部流动条件。通过大量基本结构的并行化开发了一种高通量液滴发生器。该设备能够轻松快速地将水性样品分配到数百万个均匀的皮升油滴中。使用该设备，进行了基于芯片液滴的数字聚合酶链反应（PCR），以在宽动态范围内对稀有基因进行绝对定量。
