Method and Apparatus of Using 3D Conductive Structures in Dielectrophoretic Separation Applications
Background: Researchers estimate that 80% of all machine failures are due to wear and that 1.3~1.6% of the GNP is lost to degradation of machinery due to friction-related wear. The abnormal abrasive wear due to lubricant contamination in marine diesel engines eclipses that of normal wear and the gap becomes wider with time. It was found that although oil filters used in automotive engines are designed to filter particles in the 15-30 µm range, particles with diameters below 10 µm caused 44% of the wear to engine cylinders. Physical filters that are currently used are limited because of difficulties in decreasing pore size, and the associated flow restrictions that follow when pore size is reduced. Application of dielectrophoretic forces allows manipulation of small particles, even in the submicron range.
In dielectrophoresis (DEP), the difference of polarizability between particle and solution in a non-uniform electric field gives rise to a net force acting on the particle. In positive dielectrophoresis, particles are more polarizable than the solution and tend to move toward high-field regions, and in negative dielectrophoresis, particles are less polarizable than the solution and migrate toward low electrical field regions. Dielectrophoresis has the advantage of being able to apply forces onto uncharged species (such as cells or carbon nanotubes). Separation using DEP has been demonstrated many times, but because the DEP force decays rapidly as you get away from typical planar electrode arrays, there have been difficulties creating high throughput separation devices. 3D electrodes can extend the field into the solution, and effectively increase the volume of separation, but even when using 3D electrodes, it is difficult to create a high efficiency separation device with high separation efficiency because of the difficulty of washing away only certain particles. Technology: Researchers at the University of California, Irvine have developed novel 3D dielectrophoretic designs for high efficiency separation and have demonstrated such a system for filtration of submicron contaminants from lubricants. The system also allows for online monitoring of contaminant levels. The novel high throughput electrode designs could be used for other applications were separation, filtration, or concentration of species is needed. Application: Although the present invention was demonstrated in the field of tribology (lubrication) and is currently being investigated for use in biomedical applications, the invention can be used in any application involving separation, filtration, or concentration of species.
Three example uses for DEP separation devices are listed below:
1. Filtration and online monitoring of lubricants.
2. Separation of carbon nanotubes: Currently, there is no way to grow nanotubes homogeneously. There is great interest in separating semiconducting carbon nanotubes from metallic carbon nanotubes.
3. Separation of cells: Separation of viable or diseased cells from the blood stream or from a heterogeneous cell culture or tissue sample can greatly improve the accuracy and sensitivity of diagnostic techniques. It increases the signal-to-noise ratio for a bio-assay by separating away unwanted variables and it is an amplification technique that allows early detection by concentrating the species of interest.
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