Experiment And Simulation Research On Controllable Positioning Of Particles Based On Dielectrophoresis

Performing various operations on microparticles based on dielectrophoresis,such as stretching,capturing,separating,enriching,positioning,and fusion,is of great significance for the diagnosis and treatment of tumor cells,drug screening,water quality monitoring,and biochemical detection.Particle positioning is the first step in performing various complex operations on particles on a microfluidic platform,and is the primary problem to be solved in many studies.Particle positioning is affected by many factors,so studying particle positioning and analyzing its dynamic process is of great significance for predicting particle movement and precise positioning.This topic is based on dielectrophoresis to realize the controllable localization of polystyrene(PS)microspheres and Hela cells,explore the localization experiment rules and dynamic mechanism,and carry out the following aspects of work:First,the domestic and foreign research status of localization of particles based on dielectrophoresis was reviewed.Then,the spherical particles were used as the object to discuss the principle of dielectrophoresis and its motion control mechanism,deduce the formula of the dielectrophoresis force and the velocity of the particles and study the factors affecting the dielectrophoresis force.Secondly,using glass as the substrate and gold as the electrode material,a new four-electrode integrated array chip including positioning electrodes and measuring electrodes was designed and processed.The chip was characterized by an optical microscope and an electron microscope.The results showed that the chip met the experimental requirements.The simulation model was built based on the finite element method,and the electric potential and electric field distribution were simulated and analyzed.The results showed that:the electric potential at the measuring electrode was slightly lower than the surrounding electric potential,the maximum and minimum electric potential appeared at the positioning electrode;The measurement electrode area was used as the distribution diagram of the electric field intensity of the energy trap;the position with the greater height value in the vertical direction had a smaller electric field intensity.After that,the experimental and kinetic mechanism of PS microspheres based on dielectrophoresis was studied.The results showed that when the frequency was 100 k Hz,the greater the voltage,the worse the positioning effect;when the voltage was 2 V_p-p and the frequency was greater than 10 k Hz,the greater the frequency,the worse the positioning effect;the voltage was 2 V_p-p?5 V_p-p,when the frequency was 1 k Hz?10 k Hz,the PS microsphere achieved the first controllable positioning;when the voltage was 7 V_p-p?10 V_p-p,and the frequency was 10 MHz?25 MHz,the PS microsphere realized the second controllable positioning;under dielectrophoresis-AC electroosmosis-AC electro-thermal coupling,fine adjustment of electrical parameters was very important for particle positioning.In particular,downward vortex was beneficial for positioning microspheres in the target area;dielectrophoretic force mainly affected the movement of particles in the xoy plane,while the movement in the z direction was mainly affected by the viscous force generated by the vortex.Finally,the experimental and dynamic mechanism of Hela cells based on dielectrophoresis was studied.The results showed that:at a voltage of 9 V_p-p and a frequency of 10 MHz,Hela cells achieved controllable positioning with good cell activity;in the phase-regulated cell experiment,as the phase difference decreased,the cell movement area located in the middle measurement electrode area was increased,the degree of aggregation was reduced;under different phase differences,the position of the lowest point of the electric field strength of the array chip shifted from the middle measurement electrode area to the corner area in the control unit;the dynamic simulation results under different phase differences were consistent with the energy trap theory,and the electrode pattern would define the final positioning area of the particles on the microfluidic chip.This study provides theoretical guidance for chip design and manipulation of microparticles based on dielectrophoresis,and thus,exhibits some theoretical significance and applications in the fields of biomedicine,tissue engineering,and chemical detection.