Wet Milling of Alginate Alco- and Hydrogel Composites: A Facile Top-Down Approach for Continuous Production of Aerogel Microparticles

Moving toward high-throughput production of biopolymer aerogel microparticles, in this work, the wet milling process is applied to hydrogels and alcogels. Alcogels are then converted into aerogels by well-established supercritical drying. Alginate and hybrid alginate/silica gels are used as a model system. As the Young's moduli of hydrogels significantly change when water is exchanged by ethanol, it is possible to study the effect of the gel stiffness on macroscopic and microstructural properties of the resulting aerogels. Influence of process parameters (milling speed and gap size) is also investigated. Smallest particles sizes and minimal changes in microstructure are obtained for completely solvent exchanged gels. The wet milling is shown to be a versatile method to obtain aerogel particles with diameters in the range 50-300 mu m.