Electro-Hydrodynamic Filtration (EHD): Dielectrophoresis of SiO 2 and Al 2 O 3 Particles

1. Positive Dielectrophoresis Negative Dielectrophoresis Abstract Previous work has been done to design an electro- hydrodynamic (EHD) filter to remove soot particles from fresh oil. Currently, a fifth generation working model has been designed but requires efficiency tests to ensure success. Through the use of dielectrophoresis, the filter is able to capture micro-particles as contaminated oil runs through the filter. Captivity tests on soot particles were performed. Polarizability of Aluminum Oxide (Al2O3) and Silica Oxide (SiO2) particles in lubricating oil was determined. Subsequently, captivity test on these two particles under non-uniform electric field is ongoing. Introduction The purpose of an EHD filter is to capture polarizable micro-particles from a suspension. This allows less need to change substances such as oil that becomes plagued with particles that are not possible to remove with conventional filtration systems. An EHD filter is ideal due to the fact that it is cost efficient, simple to use, and has no moving parts. The way the filter works is through the phenomenon of dielectrophoresis. Dielectrophoresis is the lateral motion applied to an uncharged particle in a non-uniform electric field . Due to the non-uniform properties of the electric field, polarization will occur. Based on a particle’s polarizability we can determine the direction of the dielectic force on the particle. If the particle is more polarizable than the medium around it, the dipole aligns with the field and the force moves the particle towards the region of high field gradient. If the particle is less polarizable than the medium, the dipole aligns against the field and the particle is repelled from regions of high field gradient. The field must have inhomogeneous (localized time-varying charge) properties in order for this to take place. Method To find the dielectrophoretic force on Al2O3 and SiO2 particles, we must first determine the real part of the Clausius Mossotti factor. The Classius Mossotti factor determines the direction of the overall dielectrophoretic force as well as the electro-rotational torque on a particle. The relation consists of two parts, the real (determines force) and the imaginary (determines torque). For our purpose, we want to find the real part in order to understand the magnitude and direction of the force. If this factor is positive it will tell us that the particles move to regions of high field gradient, while a negative factor means that particles will be repelled from those regions. We prepared 3 suspensions of silicon oxide particles in fresh oil, 1%, 10% and 20% by volume fraction. Sample complex permittivities were obtained through Broadband dielectric spectroscopy in the Keck Laboratory of NJIT. Polarizability was determined using Maxwell-Wagner Model. Electro-Hydrodynamic Filtration (EHD): Dielectrophoresis of SiO2 and Al2O3 Particles Particle Captivity Experiment Parameters • Lubricating Oil Flow Rate • Voltage • Oil Temperature Determination of Particle Polarizability Equation for force of dielectric particle Clausius Mossotti Factor Maxwell-Wagner Model Beta results Results of Efficiency Test Al2O3 SiO2 Fifth Generation EHD Filter Conclusion Preliminary result shows that Al2O3 is more polarizable than SiO2 particles in lubrication oil. Particle captivity results for Al2O3 showed a beta ratio of 19.31 at 400V compared to a ratio of 3.37 at zero voltage which amounts to 94.8% efficiency. The result for SiO2 particles is in process as data for its captivity under electric field is still being gathered. These results demonstrates the advantages of EHD filter in contaminant removal. Sponsors: National Aeronautics and Space Administration (NASA) NASA Goddard Space Flight Center (GSFC) NASA Goddard Institute for Space Studies (GISS) NASA New York City Research Initiative (NYCRI) Contributors: New Jersey Institute of Technology Dr. Boris Khusid Ezinwa Elele , Graduate Student Ian O’Leary, NYCRI High School Apprentice