Electrohydrodynamics of electrosprayed charged droplets in a vorticial flow
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Lee, Jung Yun
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Abstract
Electrospray ionization has become a popular method to produce ultra-small charged liquid droplets. The coupling of electrospray ionization to mass spectrometry (ESI-MS) has enabled determination of the composition of complex biological samples with applications including biomarker discovery and disease diagnosis. Improvement in ESI-MS sensitivity can be achieved via effective desolvation of electrosprayed charged droplets and more efficient transport of dry analyte ions into the mass analyzer. Based on a novel implementation of swirling flow, an ESI-MS interface developed as part of this dissertation exploits a vorticial gas flow to advantageously alter the spatial size-distribution of droplets. Numerical and experimental studies using a prototype vortical MS interface indicate that large droplets are displaced to the periphery of the electrospray plume under the influence of the outward inertia of the vortex flow, resulting in reduction in chemical noise with improvement in sensitivity. The objective of this research is to increase the understanding the behavior of electrosprayed charged droplets via theoretical and experimental studies focused on (1) the effects of a vortical flow on the spatial size-distribution and (2) the effects of the coupling of a vorticial flow to an active suction flow on droplet transmission. Multiphysics modeling considers vortical flow hydrodynamics in the presence of suction, applied external electric fields, and inter-droplet electrostatic interactions (space charge) to study their impact and ability to control charged droplets of differing size and charge. Experimental flow visualization and ion current measurements are used to provide basic insight into the phenomena and validation of model predictions. The successful implementation of the work presented in this dissertation provides valuable input and insights into the vorticial ESI-MS interface design and operation.
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Date
2020-05-07
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Dissertation