Mass And Position Identification Of Ultrafine Particles Based On Rectangular Thin Plate Microcantilever

The development of micro-electro mechanical systems（MEMS）processing technology enable the design and manufacture standard of high precision micro cantilevers.The ultra-micro target detection technology based on micro cantilever which meet the micro-scale measure needs for biomass,gas and partcicle in the micro-nano biology,medicine,chemistry and physics filed.has received great attention in recent decades.Most of the mechanical problems in the study of micro-cantilever ultra-fine target detection can be attributed to the identification problem of micro-cantilever surface attachment targets.Up to now,the limitation in this field is restricted in one-dimensional micro cantilever on the quality detection of the adsorbed particles on the surface or the uniformly adsorbed particle layer on the surface.In practical applications,the two dimension of micro-beam body and the double parameter identification of the adsorption mass and the position should be fully investigated which was researched scarely.In this paper,the thin-plate micro cantilever surface adsorption ultra-micro mass is taken as the research object,and the quantitative relationship model between the multi-target mass and position parameters attached to the surface of the single micro cantilever and the dynamic response is also established here.The resonant frequency of the microcantilever after the adsorption of the particles is analyzed.The model fully considers the effects of two-dimensional micro cantilever,size effect and adsorption effect.Two methods were measured by finite element software simulation and atomic force microscopy.The resonance frequency of the microcantilever attached particles was obtained,and the obtained frequency change value was used as the model input by the known quantity to achieve the target mass and dual identification of the location.The dynamic characteristics of thin-plate micro cantilever with multiple uniform adsorption bands attached to the surface are studied.The adsorption properties of uniform band-like adhesion mass are fully investigated,and the interaction energy between the band-like particles and the substrate are analyzed.The elastic strain energy and kinetic energy of the beam are also analyzed,given the corresponding mathematical expressions,finally leading to the energy model.For the analysis of the resonance frequency,the approximate analysis of the thin plate mode is firstly carried out,then the energy expression is modified and optimized,and the frequency of the cantilever beam vibration equation is obtained by the Lagrangian equation to solve the equation.The influence of different factors on the resonance frequency is analyzed.The influence of three important factors of the adhesion density,the number of adhesive bands and the duty cycle of the adhesion band on the resonance frequency is discussed.The dynamic characteristics of thin-plate microcantilever with multiple concentrated mass bodies attached to the surface are studied by using classical theory（regardless of size effect）and modified Cosserat theory（considering size effect）separately.One-dimensional Euler Bernoulli function combination is used to assume the two-dimensional thin plate cantilever beam vibration mode.The Lagrange equation is used to establish the dynamic model of the plate-type micro cantilever with the concentrated mass adhered.The validity of the model is verified by comparing with the published data.The bending natural frequencies and modes of the thin-plate type micro cantilever with the concentrating mass are calculated,and the examples of the concentrated masses of 1⁵ are given.Applying the model established in this paper,the influence of different parameters on the micro cantilever frequency is analyzed.The influence of different adsorption masses and position on the resonant frequency of micro cantilever is particularly studied.Finally,the effect of air damping on resonant frequency of microcantilever beam is analyzed.The inverse problem of solving the single particle and multiple particles on the surface of the flat micro cantilever is the goal of the research.According to the problem that the quality and position of the multi-object attached to the surface of the micro cantilever are obtained according to the dynamic response of the micro cantilever,further details are given to solve and verify the target.A multi-objective identification model is established by using the Rayleigh-Ritz method to establish the relationship between the mass and position of the micro-cantilever surface attachment target and its dynamic response.The model is used to derive the change of the resonant frequency before and after the attachment of the micro-beam and the quality of the mass（quality,The number and position）relationship.The finite element software was used to calculate the resonant frequencies of the micro cantilever beams obtained by particle loading before and after are taken as virtual measurement data.The quality and position of the loaded particles are detected according to the recognition algorithm.The results show that the calculated values are in agreement with the theoretical values,which means the correctness of method is verified.Through simulation analysis and theoretical calculation,the effects of different aspect ratio micro cantilever beams,particles with different adsorption masses and particles with different adsorption positions on the recognition model are analyzed.The FIB focused ion/electron double-beam micro-electron microscopy system was used to prepare micro-cantilever beams with different parameters and platinum particles of different masses and positions were deposited on the surface.The AFM system was used to measure the resonance of the micro-cantilever beam before and after deposition of platinum particles.Based on the experimentally measured frequency values and by use of the double-identification model of the surface quality and position of the micro cantilever beam established in this paper together with the least squares method,the obtained particle parameters are compared with the experimental values to prove the effectiveness of the theoretical model.The experimental data of the measurement is studied,and the influence of different parameters in practical application on the resonance frequency of the micro cantilever is analyzed,and the accuracy of the simulation analysis results is verified.Based on the currently selected microcantilever beam（micron level）and the measurement accuracy that can be achieved in the present device,particle mass and position recognition of the attached particle and microcantilever mass ratio of 0.5%are achieved,and the quality recognition accuracy can reach Pique(10^-12g)level.