Controlling the surface area, pore size and pore volume of microcapsules is crucial for modulating their activity in applications including catalytic reactions, delivery strategies or even cell culture assays, yet remains challenging to achieve using conventional bulk techniques. Here we describe a microfluidics-based approach for the formation of monodisperse silica-coated micron-scale porous capsules of controllable sizes. Our method involves the generation of gas-in water-in oil emulsions, and the subsequent rapid precipitation of silica which forms around the encapsulated gas bubbles resulting in hollow silica capsules with tunable pore sizes. We demonstrate that by varying the gas phase pressure, we can control both the diameter of the bubbles formed and the number of internal bubbles enclosed within the silica microcapsule. Moreover, we further demonstrate, using optical and electron microscopy, that these silica capsules remain stable under particle drying. Such a systematic manner of producing silica-coated microbubbles and porous microparticles thus represents an attractive class of biocompatible material for biomedical and pharmaceutical related applications.

中文翻译：

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气包水包油乳化液的多尺度微孔二氧化硅微囊

控制微胶囊的表面积，孔径和孔体积对于调节其在包括催化反应，递送策略甚至细胞培养测定法的应用中的活性至关重要，但是使用常规的批量技术仍然难以实现。在这里，我们描述了一种基于微流体的方法，用于形成大小可控的单分散二氧化硅涂层的微米级多孔胶囊。我们的方法包括生成含油的水包油型乳液，以及随后在包裹的气泡周围形成的二氧化硅快速沉淀，从而形成孔径可调的空心二氧化硅胶囊。我们证明了通过改变气相压力，我们既可以控制形成的气泡的直径，又可以控制二氧化硅微胶囊内所包围的内部气泡的数量。此外，我们使用光学和电子显微镜进一步证明，这些二氧化硅胶囊在颗粒干燥下保持稳定。因此，这种生产二氧化硅涂覆的微泡和多孔微粒的系统方式代表了有吸引力的一类用于生物医学和药物相关应用的生物相容性材料。