Research On Trapping Two Particles By Dielectrophoresis-based Microfluidic Chip

Microfluidics is the technology that used to study the control of tiny liquid samplein the structure with micron-scale. It is committed to achieve the miniaturization ofbiochemical analysis platforms in conventional chemical or biomedical laboratories.With the features of small consumption quantity, compact structure and good integrationability, microfluidics has a wide range of applications in the fields of chemical analysisand biological test. One of the most important researches in the field of microfluidics ishow to capture, manipulate and separate micro-particles in the liquid using Microfluidics.To capture a pair of different cells is an important step in the process of cell fusion.For the sake of the difficulty in capturing two particles with different sizes, new type ofmicrofluidic chip is designed based on dielectrophoresis (DEP). The chip may have ahigh pairing rate and throughput, and is easier to operate.First, the expression of DEP force was derived according to the theory of dipolemoment and main parameters which impact DEP force were obtained. The frequencyresponse curve of gold-coated microspheres was calculated and the resultant forcesapplied to particles inside the chip were analyzed and compared. The conclusion thatDEP force and Stokes force are the main contribution to particle motion was drawn. Theequation of motion was constructed.Second, the microfluidic chip to capture two particles was designed on the basis ofDEP force and Stokes force acting on the particles. Physical model of the chip was builtand numerical simulation by finite element analysis software was done. Electrode size,chip structure and control parameters were optimized. In addition, this simulation alsoverified that the chip can realized the pre-designed function by introducing suitableelectric field and flow field.Third, microfluidic chip was manufactured by MEMS processing technology. ITOglass was used as the substrate material and the desired electrode array was etched withhelp of wet etching techniques. On the glass substrate, the required lithography of SU-8micro-structure and semi-enclosed SU-8channel were processed. Finally, the cover ofSU-8micro-structure is combined together with a PDMS microchannel substrate byoxygen plasma technology and the desired microfluidic chip was obtained.Finally, the experimental platform was built to conduct experiment of particlescapture. The platform includes electrical control system and fluidic control system.Particle A was captured firstly and then particle B was captured together. More than90%sites capture single particle A successfully and about75%sites capture a pair of particleA and B. The influence of electric voltage, flow velocity on the number of captured particle was also studied. A new possible position to capture particle B was discussedconsidering the influence of the interaction forces between particle A and B.