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Updated: Jun 27, 2026
Fluorescence detection methods for microfluidic droplet platforms
Published on: December 10, 2011
Real-time probing of fast chemical reactions at the oil/water interface during microdroplet generation
Xiao Liang1, Jiyizhe Zhang2, Kunlun Gao3
1The State Key Laboratory of Chemical Engineering and Low-Carbon Technology, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, United Kingdom.
Hypothesis:
Probing the interfacial reactions during microdroplet generation is experimentally challenging, limiting the understanding of the reaction dynamics at an early stage. Real-time monitoring of the temporal evolution of interfacial tension offers a quantitative approach for probing interfacial reactions and reveals the reaction rate-control mechanisms governing the interfacial reaction process.
Experiments:
An automated microfluidic platform is developed to monitor the dynamic interfacial tension during microdroplet generation within a second, using oleic acid (HOA) and sodium hydroxide (NaOH) as a representative reaction system. The evolution of interfacial concentration of the reaction product is quantified by experiments using various reactant concentrations and flow rates, allowing for identifying the rate-control mechanisms.
Findings:
The reactions are identified to be mass transfer-controlled or adsorption-controlled at different HOA concentrations with high NaOH/HOA concentration ratios, enabling the determinations of mass transfer boundary layer thickness and adsorption rate constant of HOA. A modified Damköhler number is introduced to characterize the transition between the rate-control mechanisms. Up to one-third of HOA in microdroplets is found to be consumed during the generation stage within one second, and smaller droplets exhibit higher consumption proportions.
