One Droplet at a Time: Electrochemical Analysis of Aerosolized Microdroplet Reaction Acceleration

Microdroplets provide unique reaction environments that differ fundamentally from bulk systems, enabling accelerated reaction rates, novel pathways, and insights into complex processes such as enzyme kinetics and reactive oxygen species formation. The microdroplet interface is central to these observations, where the high surface area-to-volume ratio and interfacial effects dramatically alter reactivity. While mass spectrometry has traditionally dominated microdroplet studies through ensemble measurements, electrochemistry offers a powerful complementary approach by directly probing individual droplets. The fundamental limitation of electrochemical methods for the analysis of micrometer-sized aerosols, however, is the need for at least two electrodes. This presentation will detail the development of a novel electrochemical cell for the capture and detection of single aerosolized microdroplets. This cell was used to correlate the size of single aerosols to their ability to accelerate the reaction rate of glucose oxidase, one of life's most important enzymes. Paired with traditional droplet-in-oil stochastic electrochemistry, this work is the first apples-to-apples comparison of reaction acceleration between aerosolized microdroplets and microdroplets in an oil emulsion. We demonstrate that the gas|liquid interface accelerates the reaction rate of glucose oxidase by over an order of magnitude more than the liquid|liquid interface, providing valuable insight into the curious chemistries driven by microdroplets.