Experiment Research And Simulation On Single Ellipsoid Particle Using Dielectrophoresis

Dielectrophoretic (DEP) microfluidic chips are micron-scale platforms to treat thesmall quantity of liquid samples. The platforms show great advantages, such asminiaturization, integration, intelligence, high efficiency, high resolution, and lowpollution. So they have gotten the extensive applications in medical research,environmental monitoring, biological and chemical analysis, etc. With the continuousdevelopment of the microfluidic chip, DEP microfluidic chips go through vigorousdevelopment in different fields. It makes use of the different electricity nature betweenintermediary suspension and operating particles in non-uniform electric field tomanipulate the particles flexibly.In this paper, DEP force and force torque of the ellipsoid particles were deduced,and the mechanism to realize the stable capture was studied. The structure of DEP-based microfluidic chip was designed. Then the capture process of the particles wassimulated. Combined with the numerical simulation and MEMS technology, themicrofluidic chips and the ellipsoid particles were made, at the same time, theexperiment about the stability of capture of the ellipsoid particles was investigated.Firstly, the microfluidic theory and DEP phenomenon in microfluidic chip werestudied. Based on the polarization theory and the polarization factor of the ellipsoidparticle, the DEP force and torque imposed on particle were deduced. The influence ofrelated parameters of DEP force and torque were analyzed. At the same time, otherforces imposed on the particle were calculated and compared. Then the capturemechanism of particle in DEP force and Stokes forces has been studied, and providedthe theory basis for the simulation and experiment.Secondly, aiming at the purpose of the experiment, the structure of DEPmicrofluidic chips was designed. The related parameters of the materials and thephysical field boundary conditions were set. The distributions of velocity of flow field,voltage, the process of capture were simulated through post-processing module inCOMSOL Multiphysics software. The different capture situation was gotten underdifferent combination between different voltages and flow velocities.Thirdly, combine the advantages and disadvantages of different microfabricationtechnology, the ellipsoid particles were made based on the designed mask, siliconsubstrate and SU8-2025as raw materials through lithography method, then samplesolution of ellipsoid particles were collected by using ultrasonic technology. At thesame time, according to the simulation results of the microfluidic chip in Chapter2andthe flowchart of MEMS process, the photolithography mask territory of the microelectrode and micro channel was drawn and the microfluidic chip was realized bymicrofabrication technology.Finally, aiming at the purpose of the experiment, experimental platform was set up,including power system and fluidic system. Then experiment research was implementedusing the microfluidic chips and sample solution. Including motion phenomenon ofellipsoid particle under DEP force, analyzes the motion of ellipsoid particles in pulsedvoltage and high frequency sine-voltage. Capturing experiments of ellipsoid particleswere conducted. The influence of electric voltage and flow velocity were summarizedand the feasibility of the scheme was proved.Adopted the method of combining theoretical analysis, numerical simulation andexperimental method, the experiments of capturing ellipsoid particles were completed.The methods and conclusions in this paper could be useful and valuable for the furtherpreparation and applications of other irregular particles.