Research Of Dielectrophoretic Microfluidic Chip For Continuous Particles Separation

Dielectrophoresis techniques use AC electric field to make particles polarized for the separation and concentration of particles. The collection process of particles after particles separation based on conventional DEP is more complicated, and the consumption time is longer.In this paper, the force acting on particles in the microfluidic chip was analyzed based on dielectrophoresis and fluid flow in the mcirofluidic chip. Dielectrophoresis microfluidic chip integrated inclined interdigitated arrayed electrodes was designed for continuous cells separation to lay the foundation of the rapid preparation of cell samples. The main research contents of the paper included the following aspects:Firstly, the theory of particles separation based on DEP was studied. The expression of the dielectrophoretic force acting on the particles was derived by the dipole moment of the spherical particles and then the influence factors of the dielectrophoretic force were summarized based on the expression. The relationship between the CM factor and the frequency of three different types of particles such as polystyrene microspheres, NB4 cells and yeast cells was analyzed by using the concentric spherical shell model and the relationship between the type of DEP force acting on particles and the frequency of the AC signal, the conductivity of the solution was studied at the same time. Two kinds of particles could be separated by adjusting the frequency of the AC signal to make one subjected to positive dielectric force, while the other was subjected to negative or non DEP force.Secondly, the structure of dielectrophoresis chip was designed according to the force acting on particles in the DEP chip. Inclined interdigitated arrayed electrodes were arranged in the device to combine DEP force and hydrodynamic force to manipulation particles. Electric field distribution, intensity and the dielectrophoretic force were simulated and analyzed by using COMSOL Multiphysis software to optimize electrode parameters and height of microchannel of the dielectrophoretic chip after mathematical model of interdigitated arrayed electrodes was built.Materials of the microelectrodes and microfluidic channel were selectived. The microelectrodes was machined on ITO glass by the photolithography process and the PDMS microfluidic channel was fabricated by molding method. The complete DEP chip was fabricated after bonded together.Finally, particles separation experiments were carried out on the platform of the dielectrophoresis experiments. Amplitude and frequency of AC signal were optimized after dielectrophoretic responses of polystyrene microspheres and yeast cells were tested and then separation experiments of polystyrene microspheres and yeast cells were conducted. In order to study the effect of flow velocity on particles motion, the effect of injection pump rate on particle trajectory was analyzed, and the flow rate of the fluid was optimized. NB4 cells and yeast cells selected to be the experimental object were separated by inclined interdigitated arrayed electrodes. Yeast cells were deflected by the action of the positive dielectric force and hydrodynamic force, moving directly inclined direction along the electrodes, while NB4 cells were not deflected because of a small dielectrophoretic force, flowing along the channel. Particle separation was achieved to verify the feasibility of dielectrophoresis chip designed in this paper for continuous particles separation.