Spatial Coupled Particle Separation Driven By Three-dimensional Electrode

In recent years,laboratory-on-a-chip systems based on microfluidic platforms have attracted considerable attention in manipulating particles.The significant advantages of microfluidic devices are portability,low sample consumption,and reduced analysis time and cost.Capture,sorting,and separation are essential for particle applications,with high purity,high separation efficiency,and no labeling.Particle separation is the process of separating or separating a complex mixture of particles from a solution.Therefore,in-depth study of particle sorting can help solve the limitations of single-physics sorting.The main disadvantage of a planar electrode is that the electric field is confined near the electrode,while in a three-dimensional electrode the electric field diffuses through the cross section of the channel.The three-dimensional electrode is designed along the sidewall of the microchannel.Therefore,the DEP radiation range is increased,and the three-dimensional electrode can generate lower Joule heat and sufficient dielectrophoresis force to sort particles.First,the particle flow conditions and hydrodynamic equations at the micro-scale are explained,the influence of the principle of dielectrophoresis and the principle of inertial force on the particles is analyzed,the particles in the non-uniform electric field are deduced,and the force of the particles in the composite field is determined.Secondly,through finite element simulation analysis,the focusing structure and separation structure of the particle separation chip are designed based on the Ag-PDMS three-dimensional electrode.The software is used to simulate the two-dimensional simplified model,and the flow field,electric field and dielectrophoresis force are analyzed.The characteristics of trapezoidal structure and arched structure,the microchannel model is prepared by SU-8 photolithography process;Ag particles and PDMS are used to make composite conductive materials to prepare three-dimensional electrodes.This material has the basic properties of PDMS and has good ductility.It is easy to process into the required shape and thickness;the wet etching process is used to process the ITO transition electrode;at the same time,the reliability analysis of the sorting chip after the bonding is completed.Finally,a microfluidic separation platform based on particle chips was built,and different mixed particle test samples were prepared,and single-factor particle separation tests were carried out through the controlled variable method,including preparation experiments to verify the critical frequency,and the trajectory of single particles of polystyrene beads.The test,the particle trajectory test of different sizes and different dielectric properties,obtained the optimal sorting parameters,and finally completed the successful separation of silica beads with a diameter of 4um and polystyrene beads with a diameter of 20 um.