Micro-nanofluidic technology is widely used in food safety testing, drug screening, new material synthesis and bioengineering. Droplet microfluidic technology is an important branch of micro-nanofluidic technology. The microdroplet technology can produce high-throughput monodisperse droplets. The droplet technology overcomes many problems of continuous flow, such as small sample reagent volume, no cross-contamination, and rapid chemical reaction. So microdroplets have an important position in the fields of single cell analysis, gene sequencing, and real-time diagnosis. This review focuses on the different methods and applications of microdroplet generation in microfluidics. The droplet generation methods are passive and active methods. The passive method does not require external force, while the active method requires external force such as external electric field, magnetic field, acoustic field, and laser field. It is predicted that the quantitative generation of droplets on demand in microfluidics will be the important direction for future research. This review provides new ideas for the applications of the quantitative generation of microdroplets on demand in microfluidics.

微纳流体技术被广泛用于食品安全性测试，药物筛选，新材料合成和生物工程。液滴微流体技术是微纳米流体技术的重要分支。微滴技术可以产生高通量的单分散液滴。液滴技术克服了连续流动的许多问题，例如样品试剂体积小，无交叉污染和快速的化学反应。因此，微滴在单细胞分析，基因测序和实时诊断领域中具有重要地位。这篇综述着重于微流体中微滴产生的不同方法和应用。液滴产生方法是被动方法和主动方法。被动方法不需要外力，主动方法需要外部力，例如外部电场，磁场，声场和激光场。据预测，微流体中按需滴的定量生成将是未来研究的重要方向。这篇综述为微流体中按需定量产生微滴的应用提供了新思路。