| Microfluidics is a method that precise control and manipulate fluid of micro-nano scale.It has been widely concerned by people since it was put forward,for it has the advantages of small volume,small size,less sample consumption,high analyze speed,high sensitivity,easy integration and low energy consumption.Dielectrophoresis is a method to manipulate the micro-nano particles based on microfluidics,which depends on non-uniform electric field to transport,capture,sort and manipulate particles.It is an effective method to separate particles in microfluidic chip,and be widely used in the field of chemical analysis and biological detection,especially has important research significance and practical value in biological cell sorting and detection.It is an important prerequisite for efficient particle separation,that rational design of the dielectrophoretic microfluidic chip structure to produce non-uniform electric field in the micro flow field.In this paper,asymmetric interdigitated microelectrode array is designed based on the research of micro-nano particle separation mechanism of dielectrophoresis,and the size of the additional electric field,voltage and other parameters on the microelectrode array and micro channel were optimized.Eventually,micro-nano particles with different size can be efficiently separated in low operating voltage.The separation mechanism of different size and dielectric properties is researched,main factors that affect the particle motion in the micro channel is analyzed.Then,the finite element numerical analysis of separation process and optimization of chip structure was done in the Comsol Multiphysics.Based on the optimized working parameters of asymmetric interdigitated microelectrode array and the castle structure of micro channel,the dielectrophoresis microfluidic chip has been made.After that,the experimental platform has been set up,the different dielectric properties and size of micro-nano particles were effectively separated.Firstly,dielectrophoresis theory for separation has been analyzed.Analyzed the fluid flow characteristics,proved the equation of dielectrophoresis force based on dipole moment,then obtained the factors that can influence the dielectrophoresis force,the frequency response of yeast and polystyrene microspheres has been obtained in simulation process,different forces on the particles has been analyzed,so the equation of particle locus can be obtained.Then,a two-dimensional finite element simulation model has been built and solved.The distribution of flow field,electric field,and dielectrophoretic force in the separation channel has been calculated.Analysis the influence of channel entrance angle on separating particles,then the structure of the separation chip and size of the microelectrodes based on the simulation results has been optimized,and the motion trail has been predicted.Afterwards,asymmetric interdigitated microelectrode has been designed and manufactured of array respectively,then they were packaged to get microfluidic chip,the performance has been tested after that.On the basis of the optimized parameters obtained in simulation,we made ITO interdigitated microelectrode array using standard lithography process,and analyzed the causes of microelectrode array parameters and machining defects.Then,soft lithography method was used to made micro channel.In the end,a portable micro pump was designed to test the performance about the sealing and surface hydrophobic of the micro channel.Sandwich dielectrophoresis chip is obtained after plasma bonding.At last,the experimental platform has been set up to separate particles with two different dielectric properties and particle size.Electrical signal module,CMOD(control module)has been set up,samples used in the experiment has been prepared,mainly includes yeast and polystyrene spheres.In the experiment,we verified the frequency response of yeast,observed the movement of single sphere,then the experimental results have been analyzed. |
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