Effect And Application Of Interaction Force Of Single Particle Trap With Dielectrophoresis

The technology of single particle trap is the challenge in the fields of colloidscience, analytical chemistry and biology et al. It is also the technology on demand inmany cutting-edge research areas. Consequently，it is significant to develop a kind ofmethod that enables to trap single particle with lower cost and higher stability.Dielectrophoresis (DEP) is such a skill that is inexpensive, can provide plenty ofmanners to manipulate neutral particles locally and do not require charge or magneticconditions. With the rapid development of microfluidic technology in recent years, itbecomes possible to trap micron sized particles by DEP-based microfluidic chip.According to above statement, the effect of the short-range interaction(electrostatic interaction) between two compact particles on the performance of microscale single particle trap was analyzed in a DEP-based microfluidic chip withcontinuous fluid flow, which aims to look for the method to eliminate this negativeimpact. Then, the open channel with sudden expansion cross-section was created andthe magnitude and the distribution of electrostatic interaction force in this configurationwere obtained by numerical simulation. The results showed that electrostatic interactionforce cannot be ignored during capturing single particle. Besides, it was the main reasonto result in the failure of trapping single particle by traditional continuous DEP. Fromnumerical simulation, it was also revealed that pulsed DEP is an effective manner thathas the ability to eliminate the influence of electrostatic interaction force and obtain thehigher stability for single particle trap.On the other hand, based on the pulsed DEP trapping technology, a novel methodwas proposed to reciprocating stretch the chain of DNA molecular. First, two ends of DNA chain are connected to two particles respectively and form a Particle-DNA-Particle system. Once one particle of this system is trapped inside trapping region andthe connected DNA molecule will apply the disturbance, which is the interaction forcegenerating from another outer particle located at downstream region. When DNA chainwas stretched repeatedly under pulsed DEP force, the mechanical properties of DNAmolecules were obtained by analyzing the movement of two particles with this long-range interaction force. Numerical simulation was conduced to verify the feasibility ofthis design. The result showed that it was possible to capture and releaseParticle-DNA-Particle system periodically inside a microchannel embed micro columnarray and three pairs of strip electrodes, and hence to realize the stretch of DNA chainperiodically. Next, the oscillation movement of particles under the action of interactionforce was studied and the particles’ trajectory was obtained. Further, typical force curvesof DNA molecular during the repeated stretch process can be obtained too. Finally, mainfactors, including coefficient of elasticity of DNA and diamenter of particle wereinvestigated. All of above works are beneficial to paving the way for followingexperimental work.