Simulation And Experimental Study Of BNNSs Dielectrophoresis Regulated By Nanosecond Pulsed Electric Field

In the field of high voltage and insulation technology,the research on the orientation and arrangement of particles in the matrix controlled by the applied electric field has become a hot frontier subject,and it has huge application prospects for improving the related properties of polymer composites.For the weakly polar insulated micro-nano particles,the application of high-strength pulsed electric field can overcome the thermal breakdown phenomenon of the matrix and cause the dielectrophoresis of the orientation arrangement.However,the current research on the regulation of micro-nanoparticle dielectrophoresis by pulsed electric field is still in the initial stage of exploration,and the mechanism and related laws are still unclear.Therefore,this paper uses weakly polar boron nitride nanosheets(BNNSs)as dielectrophoresis particles,and uses ultrapure water with lower viscosity as the fluid dielectric to simulate and experimentally study the dielectrophoresis of BNNSs under pulsed electric fields.A comparative analysis of the two results reveals the basic principles of dielectrophoresis of particles under pulsed electric fields,and explores its related laws,providing theoretical basis and law guidance for engineering experimental research.First,the theory of BNNSs dielectrophoresis under pulsed electric field is analyzed.Due to the narrow pulse width of nanosecond pulsed electric field,it is necessary to judge whether particles and fluid dielectric can reach a stable polarizat ion state during pulsed high voltage.The results show that the polarization time of the BNNSs particles and the ultrapure water fluid is much shorter than the pulse width time of the nanosecond pulse voltage,indicating that both have reached a stable polarization state during the high voltage of the nanosecond pulse.On this basis,the arbitrary Lagrangian-Euler(ALE)method based on Maxwell’s stress tensor method(MST)was used to establish the mathematical and simulation model of the process.The influence of different positional parameters of two BNNSs particles on their dielectrophoresis is considered.The results show that the position parameters of α=45°,β=45° and d=2.0d*can comprehensively and simply reflect the relevant laws of BNNSs particles.Therefore,it is used as the best initial position to study the influence of pulsed electric field repetition frequency on BNNSs dielectrophoresis.Then simulate the local orientation and global arrangement of the dielectrophoresis of the BNNSs particles under the nanosecond pulsed electric field with different repetition frequencies,compare and analyze the change curves of the orientation angle of the BNNSs and the distance between the centers of the two particles at different repetition frequencies,and summarize the influence of different repetition frequencies on it.The results show that in an ideal simulation model with only two BNNSs particles,due to the cumulative effect,the speed of the BNNSs particles increases with the increase in the frequency of the nanosecond pulsed electric field,so the changes in the orientation angle and center distance are gradually accelerated;And the change curve of the orientation angle and the center distance are also gradually smoothed with the increase of the pulse electric field frequency.It can be seen that the higher the electric field repetition frequency,the better the effect.For the process of global arrangement of particles into chains,the distance between the centers of two BNNSs particles is first increased by repulsive force,and then reduced by attractive force,until after six complete pulse trains,the chain motion of head-to-head meeting is completed.Finally,an experimental platform for the microscopy system was built to observe the dielectrophoresis of the local orientation and global arrangement of BNNSs particles in ultrapure water in real time.Analyze the changes of the orientation angle and the center distance of BNNSs at different repetition frequencies,and compare and analyze the motion law obtained from the experiment with the simulation.The results show that there is a high degree of consistency in the motion law of BNNSs in the experiment and simulation,and when f=100k Hz,a long chain of about 342 um is formed.Through experimental and simulation research,the correctness of the simulation model is verified,the law of the influence of nanosecond pulsed electric field repetition frequency on BNNSs dielectrophoresis is clarified,and the optimal frequency range is determined.The research results provide a theoretical basis and regular guidance for the pulsed electric field to regulate the dielectrophoresis of insulated nanoparticles.