The fabrication of mesoporous silica microcapsules (MCs) with a highly controlled particle size ranging in the micrometer size presents a major challenge in many academic and industrial areas, such as for the development of smart biosensors and drug delivery systems with a well controlled loading and release of (bio)active molecules. We show in the present work, for the first time, that droplet-based microfluidics approach enables the fabrication of highly monodisperse MCs with a diameter ranging in the 10 mm range. The as-synthesized microcapsules exhibit a soft-like thin shell with a thickness of about 1 m, across which 5.9 nm sized mesopores form a well-ordered hexagonal 2D network. We suggested and validated experimentally a model where their formation is controlled by the solvent evaporation process at the droplet-air interface.

Figure: (A): used flow-focusing microfluidic device for the fabrication of highly monodisperse sol-gel droplets; (B&C) scanning electron microscopy (SEM) and fluorescence confocal microscopy images of synthesized fluorescent mesoporous silica microcapsules; (D) electro-osmotic-driven large distance dipolar orientation observed with solvent swollen microcapsules."