Mixing time of homogeneous/heterogeneous solutions in a micro-mixer with free impinging jets

Abstract

Abstract We have developed a micro-mixer based on a free impinging liquid-sheet jet technique. We identified a mixing position where two different solutions were mixed uniformly and evaluated corresponding mixing times in the liquid-sheet jets, with a homogeneous combination (H2O and H2O) and heterogeneous combination (C2H5OH and H2O). A quenching reaction was observed and the mixing times were evaluated to be 36 μs for the homogeneous combination (H2O/H2O) and 46 μs for the heterogeneous combination (C2H5OH/H2O). To clarify the mixing mechanism in the liquid-sheet jet, the theoretical mixing times were calculated using two different models, assuming laminar and turbulence flows. The calculated mixing times based on energy dissipation in the turbulence flow were in agreement with the observed mixing times for both H2O/H2O and C2H5OH/H2O combinations. These results indicate that turbulent mixing is a dominant mixing mechanism in the liquid-sheet jet, and that no clear interface is formed between H2O solutions and between C2H5OH and H2O solutions. The liquid-sheet jet technique provides a windowless and ultra-thin target and would be useful to investigate intermediates in mixing-driven chemical reactions, such as oxidation in solution and a folding reaction of proteins proceeding in a microsecond time scale.