Research Of Nanoparticle Manipulation Modeling Based On Least Action Principle

Using Atomic Force Microscope(AFM)to push nanoparticles has been widely used in the micro-nano scale manipulation areas.AFM can not only be used to obtain high resolution imaging by observing the sample surface,but also can be used to fabricate and manipulate the nanoscale materials.As fabricating and measuring tools at nanoscale,AFM plays an important role in different multidisciplinary analysis,such as physics,chemistry,biology and other fields.Pushing nanoparticles by AFM has been further studied by many researchers.In the procedure of pushing nanoparticles by AFM,due to the influence of the tip shape,it is very difficult to determine the force direction and the effective contact point between tip and nanoparticle.AFM can not simultaneously observe the sample surface and operate the nanoparticle.The real-time visual feedback can not be obtained.It is difficult to establish an effective operation model for manipulating nanoparticles stably.Meanwhile,the manipulation results are not controllable to reduce the maneuvering efficiency.In summary,there are still many problems in the procedure of pushing nanoparticles by AFM.In this paper,it first analyzes nano-manipulation model and other related researches at domestic and abroad.Then nanoparticle manipulation model is established for in-depth study.The work description of this thesis is as following.The establishment of the manipulation model:analyzing the pushing force of nanoparticle,pushing force is the minimum based on the least action principle.The rule is founded when nanoparticle is manipulated in the rotation and translation.The equilibrium equation is established by this rule.Considering the effective contact point position between the nanoparticle and the tip,the relation of the pushing direction and the resultant force is researched.The manipulation model about pushing nanoparticle is established.Maneuvering the nanoparticle is modeled to predict its position after manipulation.Nanoparticles position is changed in different time after the operation by AFM.The moving trajectory of the nanoparticles is simulated.The motion curve is fitted out.Model solving and influencing factors:due to the complexity of the formula,it is difficult for the manipulation model to get analytic solution.Numerical methods including Runge-Kutta and Monte-Carlo are used for solving equation of model.Analyzing the influence of the model parameters on the accuracy of the model,considering the influence of the probe and nanoparticle effective radius on the simulation experiment,the tip shape affects the push direction.The simulation step plays an important influence on the model results.The definite method is given to estimate the pushing force direction,then the parameters of the model are calibrated.Simulation experiment verification:through the comparison between simulation experiment and real manipulation results,the parameters of the calibration are adjusted to achieve the best results.A large number of experiments on the foundation of experimental analysis and algorithm program debugging illustrate the nanoparticle manipulation model efficiently.According to the actual manipulation results,it is proved that the manipulation model can effectively predict the nanoparticles trajector.The model also plays a role of guiding nano-manipulating,reducing scanning time and improving nano-manipulation effect.Through comparison between results of simulation experiment and the actual operation,the parameter of the friction coefficient has been calibrated.This research work is useful for further studying about AFM manipulation and the friction analysis between the AFM tip and sample.