Efficient Fabrication of Well-Shaped and Monodisperse Silica Aerogel Microspheres by Microfluidics and Rapid Ambient Pressure Drying

Silica aerogel microspheres are known for their unique features which are better than those of the bulk silica aerogel, including excellent biocompatibility and flowability, and have a broader application prospect for biomedicine, adsorption purification, catalytic reactions, energy storage, and sensing. However, the production of high-quality silica aerogel microspheres still poses significant challenges, such as low sphericity, difficult size adjustment, uneven morphology, and a prolonged drying process, especially ambient pressure drying for several hours. Herein, we report a novel process for efficiently synthesizing high-quality silica aerogel microspheres through the use of microfluidic and ambient pressure drying techniques. In the novel process, the colloidal sol microdroplets were prepared in stepped T-microchannels to achieve size adjustment with a narrow diameter distribution and good sphericity. A new drying process under ambient pressure at high temperature was proposed, which realized the rapid drying under ambient pressure for 10 min while the linear shrinkage of the microspheres was less than 5%. Highly spherical and uniform silica aerogel microspheres with diameters adjustable from 50-300 μm were successfully fabricated. The prepared silica aerogel microspheres exhibited high mesoporosity along with ultralow density, high specific surface area, and high hydrophobicity. In addition, the factors that significantly influence the final morphology of the silica aerogel microspheres have been thoroughly researched. This innovative process offers a new approach for the efficient synthesis of high-quality silica aerogel microspheres.