Design/Analysis of Traveling Wave Dielectrophoresis Pump
Date Issued
2007
Date
2007
Author(s)
Yeh, Yu-Ming
DOI
zh-TW
Abstract
The traveling wave dielectrophoretic pump studied in this thesis is essentially a straight micro channel with electrode array(s) built on one or two of its walls. A traveling wave electric field is generated inside the channel when an ac field is applied to the electrodes with suitable phase shift between neighboring electrodes. A generalized dielectrophoretic force, including both the traditional and traveling wave dielectrophoretic force, is imparted on the suspended dielectric particles in fluid (such as our cells in blood) inside the channel. Under suitable conditions, the particles move along the channel. As the particles move, they drag their neighboring fluid, and thus the whole medium is delivered (the two phase suspension medium is being pumped). This goal of this thesis is to study such a pump, and several works were completed. (1) The electric fields for different electrode arrangements have been solved via analytical and numerical method. (2) When the pump is operated at frequency shifted from its optimized design frequency (when the real part of the Clausius-Mossotti factor equals zero), the traditional dielectrophoretic force will exert a force to the particles, which is opposite to the driving traveling dielectrophoretic force, when they entered the region above the electrode region. Such opposite force slows down the particles which degrade the pumping efficiency, or even blocks the particles which make the pump fails. In order to overcome such a drawback, a remedy is proposed, which is to add two assistant electrodes before the electrode array. When the assistant electrodes are operated at phase 90 and 270 or 180 and 270 (0 for the first electrode of the array) at a suitable voltage less than that of the electrode array, the opposite traditional dielectrophoretic force can be reduced. Also the pumping efficiency is enhanced with the assistant electrodes. At optimized design frequency, the average velocities of particles at the pump exit are 100 micron/s and 160 micron/s, respectively, for a typical case without and with assistant electrodes. (3) Calculation of two-phase suspension flow under the electric field is required for studying the pumping efficiency. We have updated an existing computer program by modifying the boundary conditions for particle impact and including variable electric properties and of the fluid, which are crucial for a correct simulation. For a typical case with assistant electrode, the numerical average velocity of the particles at exit accounting for the variable electric properties is 13.46 micron/s, which is about 10% less than the corresponding experimental result, 15 micron/s.
Subjects
旅波
介電電泳
幫浦效能
traveling wave
dielectrophoresis
pump performance
Type
thesis
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