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Understanding Electrokinetics in Microdroplets: Concentration Redistribution, Injection of Chemical Species, Cell Lysis and Modulation of Reaction Rates
Thursday, March 11, 2021: 9:30 AM - 9:50 AM
Speaker(s)
Description
Droplet microfluidics provides a versatile means to manipulate chemical or biological entities. We recently developed a method to actively manipulate droplet contents electrokinetically. When droplets were positioned between two cation permselective membranes under a voltage bias, the concentration of an anionic fluorescent tracer was redistributed within the droplet, resulting in more than 15-fold localized enrichment. We have most recently extended this method of electrokinetic manipulation of droplet contents to the lysis of individually encapsulated cells followed by an enrichment-enhanced assay of their enzymatic content. In this presentation, we will discuss the underlying mechanisms that govern in-droplet electrokinetic manipulation. Various physiochemical parameters are studied both experimentally and computationally. Specifically, this study examines the impact of buffer concentration, applied electric field, and device configurations on concentration profiles and fluid flow patterns within the droplets. To simulate these complex electrokinetics, the coupled Navier-Stokes and Poisson-Nernst-Planck equations were solved using finite element methods. This numerical method was validated with analytic solutions of electroosmotic flow and when applied to in-droplet electrokinetics, yielded good agreement with experimental results. Moreover, the simulation results allow for the individual roles of the coupled physics to be delineated. For example, in-droplet cell lysis can be explained by three distinct mechanisms: high electric field, fluid shear stress, and osmotic pressure due to localized ion depletion. The simulation allows for quantitative investigation of each mechanism of cell lysis, which is difficult to accomplish by experimentation alone. Our findings are significant because they provide fundamental insights that inform the development of in-droplet electrokinetic methods. The financial support for this research is from NSF under award no. 1849109.
Additional Info
Keywords: Please select up to 4 keywords ONLY:
Biomedical,Enzyme Assays,Membrane,Method Development
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