Study Of The Particle Manipulation In Off-Chip Dielectrophoretic Chips

With the development of the microfabrication and micro-fluidic technique, lab on chips has become one of the most popular research fields. Many manipulations about cells or viruses can be operated on lab chips, such as trapping, alignment, separation, patterning, characterization and purification. So far, a lot of techniques have been explored by researchers, among them dielectrophoresis is much more attractive which is easily integrated for its simple structure and microsize. Moreover, dielectrophresis has low requirement for the samples, none pre-processing and high level of automation. It also shows high accuracy and stability. Therefore, manipulations of micro-particles based on dielectrophoresis has become a significant research subject now.In this paper, four typical methods of dielectrophoresis are reviewed i.e. non-flow(current) DEP, micro-flow DEP, light-induced DEP and insulator-based DEP. Then the shortages of these methods are discussed. On the base of the disscussion, a novel structure of off-chip dielectrophoresis is designed and its action principles are introduced. Furthermore, the particle motion in the chips are modeled and calculated, and the affected factors of particle behaviors are studied. According to the calculated results, a series of particle-experiments are implemented in the designed off-chip dielectrophoretic system. At last, continuously particle separation, wall-hitting separation, paticle sieving and alignment are realized. The relevant results are listed as follow:(1) The off-chip dielectrophorestic chips related theory are introduced, and the key parameters of the chips are calculated and designed. Based on the equivalent dipole moment theory of DEP, the affecting factors of the DEP forces are discussed. Then the off-chip DEP structure is presented, and the particle stress function is studied. On the base of the theories, the parameters of the chips, such as the materials and thickness of of the off-chip film, the geometrical parameters of the electrodes, are calculate and desinged.(2) The DEP experimental platform used for particle manipulation is built and constructed. The platform consisted of three parts:observation subsystem, electric signal subsystem and chip subsystem. Firstly, the observation subsystem is set up on the base of a microscope, which is equipped with fluorescent module, dark field module and CCD. secondly, the electric signal subsystem utilize the SCM technology to control the electrocircuit with electricity of high frequency and voltage. This subsystem offers the nonuniform electric field, the key point for DEP effect. Thirdly, the micro channel and the electrodes chips are manufactured with the technology of photolithography, injection molding, PCB and so on. Lastly, we put all the subsystems together to complete the platform for the following experiments.(3) The simulation and experimental verification of particle behavior in off-chip DEP chips are carried out. The electric/fluid field distribution in the chips are calculated through the Comsol and Matlab software. On that basis, particle motion control equation is established and the motion is simulated by step iteration. Through the simulation, the characteristic "S" type curve track is found. According to the simulation, three factors, the voltage U, the chip-angle θ, the flow velocity u, are discussed.Further more, three important parameters-hl、h2、ΔH is defined to predicate the deflecting effect of the particles. According to the calculated results, a series of particle-experiments are implemented in the designed off-chip dielectrophoretic system to certificate the simulation. The experimental results are in accordance with the simulation.(4) Particle manipulations based on the off-chip DEP are carried out and realized. According to the calculated results, Two sized particles,5-μm and 10-μm, are continuously separated by managing the related affected factors. Based on this, wall-hitting separation is realized and the effective separating distance reaches 10mm which is far more reliable. Apart of this, paticle sieving chips is established by decrease the number of the electrodes. Samples with particles can be purified and the particles can be extensively sieved by different sizes. And furthermore, the particles are dynamically arrayed by the chips, which is in favor of the cell culture and tissue culture.