Separation Of Microparticles Using Insulated Dielectrophoresis Induced By Microchannel Structure

Microfluidic-based detection can be used in several new fields such asmechanical engineering, biomedicine, chemical engineering, etc, due to itsminiaturization, integration, portability and low-cost. Manipulation of micro/nanoparticle is a key procedure in the research on complex medium. Common methodsfor manipulating micro particles include hydrodynamic force, acoustic separation,magnetic attraction, optical control and electric manipulation. Among them,dielectrophoresis (DEP) is the most effective method to achieve chip integrationand portability. Alternating current (AC) electric field is usually used to generateDEP force. Traditionally, DEP uses electrodes deposited on glass to manipulateparticle. For active cells, contacting with electrode would both pollute the electrodeand destroy cells. Therefore, contactless insulated DEP generated by micro channelstructure is used to separate particles. The research lays the foundation forseparating active cells.First, the phenomenon of DEP was studied and the formula of DEP force wasderived. The effects of frequency, voltage, size of particle and dielectric propertiesof medium and particle were analyzed. The motion of particle in micro-channel wasanalyzed by considering the effect of fluid and DEP force. Equations of particlemotion were derived based on simplified Lagrangian-model. Proper frequency andmedium conductivity were examined by analyzing the electrical effect on fluid.Second, the characteristics of insulated DEP in different structures werechecked by simulations. On this basis, micro-channels were designed to collect andseparate particles. The effect factors of DEP were analyzed by simulation andparticle tracing was used to describe the motion of particle.Then, mask was designed. Chips were fabricated based on needle-electrode.Particle samples and medium were prepared before setting up experimental system.Three kinds of mixed particles, including10μm/3μm polystyrene (PS) microspheres,10μm/25μm PS microspheres and native/gold coated PS microspheres, were used inexperiments for separation. The effects of fluid velocity and voltage were analyzed. Finally, chip was designed for separation of three kinds of particles.Acupuncture needles were used as electrodes. The effects of position of electrodeswere analyzed. The most reasonable position was obtained. Based on this, the effectof fluid velocity, voltage and frequency was analyzed. High-effic iency experimenteffect of separation was obtained. Experimental results show that insulated DEP issuited to separate micro particles and this method has potential applications.