Optimized droplet-based microfluidics scheme for sol-gel reactions.

A droplet-based microfluidic reaction scheme is developed where the chemical reactants are dispensed with precise volume control into pairs of droplets. The reaction is activated by coalescing droplet pairs and fast mixing inside the coalesced droplets. Furthermore, the pre-processing of the chemical products is included in the microfluidic device. This reaction scheme allows the performing of precisely volume controlled reactions and long operation times without any clogging even if precipitates or sticky gels are formed during the reaction. Using this approach and optimizing the reaction parameters, we generate mesoporous silica microspheres from a rapid gelation optimized sol-gel synthesis route. The produced silica particles have a superior surface area of 820 m(2) g(-1) and a narrow pore radius distribution of around 2.4 nm.