Controlled Production of Monodispersed Silica Microspheres Using a Double Step-Emulsification Device

We explore droplet based microfluidics to perform chemical reactions within microfluidic channels. By dispensing the different chemicals in droplets and subsequently merging the droplets containing different chemicals, the reactive mixture never gets in contact with the walls of the surrounding microfluidic channel. Using this approach we can realize chemical reactions for gels or precipitates, which are neither possible in single phase microfluidics, nor in droplet based microfluidics if the chemicals are mixed prior to dispersing the droplets. We explore this explicitly for the production of porous silica particles from sol-gel chemistry. All processing steps ranging from droplet production, synchronization of the droplets containing the different chemicals, combining the droplets, mixing and post processing are discussed and optimized for the particular demands.