Continuous-flow synthesis of amphiphilic rhodamine B-polymethylsilsesquioxane fluorescent microspheres for micro-PIV analysis

Tracer particle is a key element in the micro-PIV flow field measurements. The oil-dispersible tracer particles are mainly obtained by post modification, resulting in relatively poor uniformity and dispersibility. In this work, we developed a molecular-level amphiphilic tracer particle, i.e., rhodamine Bpolymethylsilsesquioxane (RhB-PMSQ) fluorescent microspheres. The RhB-PMSQ microspheres were synthesized in a continuous-flow microreaction system with the aqueous solution of NH4OH and RhB as the continuous phase and methyltrimethoxysilane (MTMS) as the dispersed phase. The microreaction system consisted of a T-junction micromixer, a capillary reactor for MTMS hydrolysis, and a millimeterscale tubular reactor for condensation reaction. By controlling the condensation degree of surface Si-OH groups, the hydrophilic and hydrophobic RhB-PMSQ microspheres could be synthesized with the same reaction system, and they could be uniformly dispersed in the aqueous phase and oil phase, respectively. The density, pore structure, and fluorescence property of the RhB-PMSQ microspheres were investigated in detail. The RhB-PMSQ microspheres were employed as the tracer particles of water and liquid paraffin, and the two-phase velocity profiles were measured via micro-PIV technique in a step T-junction microchannel. The micro-PIV results indicated that amphiphilic RhB-PMSQ microspheres could serve as the tracer particles for the flow field measurement both of aqueous phase and oil phase.(c) 2022 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Automated summary

In this study, molecular-level amphiphilic tracer particles were synthesized using a continuous-flow microreaction system. These particles were successfully dispersed uniformly in both aqueous and oil phases, and used for measuring velocity profiles in a two-phase flow field.