Date of Graduation

7-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor/Mentor

Ingrid Fritsch

Committee Member

Colin Heyes

Second Committee Member

David Paul

Third Committee Member

Steve Tung

Keywords

Pure sciences, Magnetohydrodynamics, Microfluidics

Abstract

Magnetoconvection is a promising phenomenon for developing new electrochemical-based microfluidic flow devices with unique capabilities, such as easily switching flow direction and adjusting flow speeds and flow patterns as well as avoiding bubble formation. In order to develop these devices it is necessary to study the underlying forces. Four contributions toward fluid flow were considered. The first and foremost is the magnetohydrodynamic force, which is the magnetic component of the Lorentz force and governed by the right hand rule. It generates the majority of the convention, and is the most well-known. The second is the gravitational force, which causes convection under non-uniform solution density. In electrochemical systems, it is induced by the change in solution composition near an anode or cathode caused by the oxidation or reduction of electroactive species. The third is the magnetic gradient force, and is present when there are paramagnetic species, which are easily produced in electrochemical systems, and a non-uniform magnetic field. The fourth is the paramagnetic concentration gradient force, the magnitude of which lies in controversy. To study these forces, a solution containing microbeads and redox species were placed in an electrochemical cell, and fluid motion was monitored with bead video microscopy in presence and absence of an externally applied magnetic field. To study density gradients, the ferricyanide-ferrocyanide redox couple was used without a magnet. To study all the forces, the effect on fluid flow in the presence and absence of a magnet during deposition and stripping at electrodes in solutions containing paramagnetic Cu(II) and diamagnetic Pb(II) ions was performed.

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