Hydrogels are biocompatible materials commonly used in biological applications, such as cell encapsulation, tissue engineering and drug delivery systems. The use of hydrogels in the form of microparticles brings, for several purposes, many advantages, since the particles have a high surface-to-volume ratio and they can be delivered inside microscale structures such as blood microvessels and tissues. Microfluidic devices are a promising approach to produce hydrogel microparticles because they enable a high precision control of the flow streams during the microfabrication process, leading to microparticles with precise size, shape, mechanical properties and cross-linking density. In this review, the focus is put on the most important features to be considered when producing hydrogel microparticles through microfluidic devices. First, the design strategies of microfluidic devices, the selection of the operating conditions and the importance of surfactants are analyzed. Then, the most important gelation mechanisms are reviewed. Afterwards, the most commonly used hydrogel materials are introduced, and their properties are referred. Finally, the different methods to control the size, shape and particle microstructure are discussed and the main challenges for the future are addressed.

水凝胶是生物相容性材料，通常用于生物应用，例如细胞封装，组织工程和药物输送系统。出于若干目的，使用微粒形式的水凝胶带来许多优点，因为微粒具有高的表面体积比，并且它们可以在诸如血液微血管和组织的微尺度结构内递送。微流体装置是生产水凝胶微粒的一种有前途的方法，因为它们能够在微加工过程中高精度控制流动流，从而产生具有精确尺寸，形状，机械性能和交联密度的微粒。在这篇综述中，重点放在了通过微流体装置生产水凝胶微粒时要考虑的最重要的特征。第一，分析了微流体装置的设计策略，工作条件的选择以及表面活性剂的重要性。然后，回顾了最重要的凝胶化机理。然后，介绍最常用的水凝胶材料，并介绍其性能。最后，讨论了控制尺寸，形状和颗粒微结构的不同方法，并讨论了未来的主要挑战。