Efficient Fabrication\nof Well-Shaped and Monodisperse\nSilica Aerogel Microspheres by Microfluidics and Rapid Ambient Pressure\nDrying

Silica aerogel microspheres are known for their unique\nfeatures\nwhich are better than those of the bulk silica aerogel, including\nexcellent biocompatibility and flowability, and have a broader application\nprospect for biomedicine, adsorption purification, catalytic reactions,\nenergy storage, and sensing. However, the production of high-quality\nsilica aerogel microspheres still poses significant challenges, such\nas low sphericity, difficult size adjustment, uneven morphology, and\na prolonged drying process, especially ambient pressure drying for\nseveral hours. Herein, we report a novel process for efficiently synthesizing\nhigh-quality silica aerogel microspheres through the use of microfluidic\nand ambient pressure drying techniques. In the novel process, the\ncolloidal sol microdroplets were prepared in stepped T-microchannels\nto achieve size adjustment with a narrow diameter distribution and\ngood sphericity. A new drying process under ambient pressure at high\ntemperature was proposed, which realized the rapid drying under ambient\npressure for 10 min while the linear shrinkage of the microspheres\nwas less than 5%. Highly spherical and uniform silica aerogel microspheres\nwith diameters adjustable from 50–300 μm were successfully\nfabricated. The prepared silica aerogel microspheres exhibited high\nmesoporosity along with ultralow density, high specific surface area,\nand high hydrophobicity. In addition, the factors that significantly\ninfluence the final morphology of the silica aerogel microspheres\nhave been thoroughly researched. This innovative process offers a\nnew approach for the efficient synthesis of high-quality silica aerogel\nmicrospheres.