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Maximizing fluid delivered by bubble free electroosmotic pump
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Tawfik, Mena E.. Maximizing fluid delivered by bubble free electroosmotic pump. Retrieved from https://doi.org/doi:10.7282/T3NZ8B35

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TitleMaximizing fluid delivered by bubble free electroosmotic pump
NameTawfik, Mena E. (author); Diez, Javier (chair); Rutgers University; Graduate School - New Brunswick
Date Created2017
Other Date2017-01 (degree)
SubjectMechanical and Aerospace Engineering, Microfluidics
Extent1 online resource (xii, 70 p. : ill.)
DescriptionIn generating high electroosmotic flows (EO) for use in microfluidic pumps, a limiting factor is faradaic reactions which are more pronounced at high electric fields. These reactions lead to bubble generation at the electrodes and pump efficiency reduction. The time taken for gas bubbles to start forming on an electrode operates in a stagnant aqueous solution is driven by the dissolved gas mass-transfer near the electrode. This is the result of two processes that compete with one another. One adds dissolved gas molecules from the chemical reactions at the electrode surface and the other diffuses these molecules towards the bulk. Using this mechanism, a model is proposed that can predict the dissolved gas supersaturation concentration up to the onset of bubble nucleation at the electrodes (heterogeneous nucleation). Experimental measurement of the bubble onset nucleation time is incorporated within this model to calculate the critical supersaturation concentration for dissolved hydrogen and oxygen gas. The results show a strong link between the applied current density and the supersaturation concentration at the electrode surface. The gas bubble nucleation time at low current densities (low production rate) can be easily measured by monitoring the electrode surface. However at high current density, the nucleation times are too short to be accurately experimentally measured by common techniques. A new experimental technique is proposed to quantify, control and measure the bubble nucleation time at high current densities (high production rate) by alternating the applied voltage waveform. A relation is obtained that predict the onset of bubble nucleation showing an excellent agreement with the measurement. The onset of gas generation for high current density EO pumping depends on many parameters including applied voltage, working fluid and pulse duration. The onset of gas generation can be delayed and optimized for maximum volume delivered in the shortest time possible. This has been achieved through the numerical model proposed to predict the onset of gas generation during EO pumping using an optimized pulse voltage waveform. This method allows applying current densities higher than previously reported. Optimal pulse voltage waveform (OPW) are calculated based on the previous theories for different current densities and electrolyte molarity. The Electroosmotic pump performance is investigated by experimentally measuring the fluid volume displaced and flow rate.
NotePh.D.
NoteIncludes bibliographical references
Noteby Mena E. Tawfik
Genretheses, ETD doctoral
Persistent URLhttps://doi.org/doi:10.7282/T3NZ8B35
Languageeng
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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