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Colliding-Droplet Microreactor: Rapid On-Demand Inertial Mixing and Metal-Catalyzed Aqueous Phase Oxidation Processes
Ryan D Davis1, Michael I Jacobs1,2, Frances A Houle1
1Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Analytical Chemistry
|October 31, 2017
Summary
Researchers developed a new method to study reactions in airborne microdroplets by colliding them. They found that collision speed and angle significantly impact mixing times, crucial for precise chemical kinetics studies.
Area of Science:
- Chemical kinetics
- Microfluidics
- Aqueous chemistry
Background:
- Investigating microdroplet reaction kinetics requires precise temporal and spatial control.
- Merging microdroplets is a key technique, but airborne droplet mixing dynamics are not well understood.
Purpose of the Study:
- To present an on-demand experimental approach for initiating reactions and characterizing mixing dynamics of colliding airborne microdroplets.
- To establish a microreactor for studying chemical kinetics with high spatial and temporal control.
Main Methods:
- Utilized streak-based fluorescence microscopy to analyze mixing dynamics of colliding airborne microdroplets (40 ± 5 μm diameter).
- Generated controlled monodisperse microdroplet streams for collision experiments.
- Investigated mixing times as a function of collision velocity and geometry (head-on vs. off-center).
Main Results:
- Achieved submillisecond mixing times, with head-on collisions yielding <200 μs at ~6 m/s.
- Off-center collisions showed longer mixing times, increasing by up to 6x at high velocities (>1 m/s).
- Droplet fragmentation and incomplete mixing occurred at collision velocities >7 m/s.
Conclusions:
- Airborne merged microdroplets offer a controlled environment for studying rapid reaction kinetics.
- Collision parameters (velocity, geometry) must be optimized for efficient mixing.
- The developed microreactor accurately models bulk-phase kinetics for bimolecular reactions, validated with Fenton's reaction.
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