A microfluidic approach for controllable synthesis of TiO2 submicrospheres

TiO 2 submicrospheres are used in dye-sensitized solar cells and Li-ion batteries to enhance energy conversion efficiency and volumetric performance. In this study, a microfluidic chip was designed for the realization of the continuous controllable synthesis of TiO 2 submicrospheres. The chip utilizes two T-channels to discrete dispersed phases into droplets, and a Y-channel to fuse the two dispersed phase droplets. The droplets generation process, the influencing factors of droplet length and the fusion process of droplets were investigated. The effects of the flow rate ratio of titanium oxysulfate and ammonia solutions, microchannel geometrical profiles including the Y-channel entrance angle on the size of the synthesized TiO 2 were studied. The length of the generated droplets was found to decrease with increasing continuous-phase flow rate, and increase with increasing dispersed-phase flow rate and microchannel cross-section area. When the flow rate ratio of titanium oxysulfate solution and ammonia solution was 1:1, the average diameter of TiO 2 spheres synthesized was the smallest, around 300 nm. Increasing the microchannel cross-section and Y-channel entrance angle were beneficial in obtaining larger TiO 2 submicrospheres. This proposed microfluidic strategy has the potential for applications required continuous synthesis of TiO 2 submicrospheres with controllable sizes. • A microfluidic chip was designed for continuous synthesis of TiO 2 submicrospheres. • The generation and fusion process of droplets in microfluidic chip were investigated. • When the solution flow rate ratio was 1:1, the size of TiO 2 spheres was the smallest. • Increasing the microchannel cross-section and Y angle can obtain larger TiO 2 spheres.