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Investigation of the Geometry Effect on Electrokinetic Instability in Microflows

Mohammadzadeh, Alireza | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51799 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saidi, Mohammad Hassan
  7. Abstract:
  8. Lab-on-a-chip devices have gained a lot of attention in chemical and biomedical analyses during the past two decades. These devices employ microfluidics basics and fundamentals to combine multifold laboratory processes in one single portable chip. The electric field has been often used in most microfluidics applications for the ease of sample control as well as become easily integrated to other chip components. Instabilities in microflows would occur when two fluids of different electric properties are exposed to an adequately strong electric field. Studying these electrokinetic instabilities is not only important for the fundamental studies but also for practical applications in micromixers since these flow instabilities are the main concept behind electrokinetic micromixers. In this study, a simulation of the electrokinetic instability phenomenon has been conducted based on a numerical transient model in COMSOL Multiphysics. This model is developed based on the experimentally measured data of the electric conductivity previously reported in the literature. This model which is developed based on depth-averaged governing equations can predict the threshold electric field accurately for the T-shaped microchannel in comparison to experimental results. Using this validated model, the effect of increasing inlet channel angle with respect to the vertical line (i.e., decreasing the inlet channel angle of the Y-shaped microchannel with respect to symmetry line) on the threshold electric field for the onset of electrokinetic instabilities was investigated. The results revealed that the threshold electric field (or applied voltage) increases with the increase in the inlet channel angle
  9. Keywords:
  10. Electrokinetic Instability ; Microfluidic System ; Micromixer ; Electroosmotic Flow ; Ferrofluid

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