Atomic Force Microscopy Non-resonant Magnetic-drive Technology And Its Application In Micro/Nano Mechanical Measurement

Atomic Force Microscopy(AFM)is one of important methods to characterize mechanical properties of materials at micro-nano scales.It can reveal mechanical behaviors of materials and provide approaches for research in frontier fields such as biomedicine and micro/nano manufacturing.How to improve the nanomechancial measurement range of a single probe,widen the frequency range of dynamic viscoelasticity measurement,and increase the efficiency of adhesion measurement are unsolved problems for traditional AFM measurement method.Starting from the driving method,this dissertation builds the magnetic-driven system of AFM,and develops the magnetic torque driving method with large output force(n N ～μN),broad driven frequency(～ hundreds of kilohertz)and the high-efficiency magneticdriven probe preparation technology.It laid the foundation for the application of magneticdriven AFM in the field of micro-nano mechanical measurement.Based on a non-resonant magnetic-driven AFM,a broad modulus range nanomechanical measurement method for soft materials were developed.A unified sensitivity method was proposed to solve the problem of restricting the measuring range of the probe Young’s modulus.Combined with the peak force modulus classification adjustment algorithm to the sample,the effective control of the indentation depth during the scanning process was realized.Through the nanomechanical measurement of polymer materials and bacteria under different environments(air,water,etc.),it is proved that this method can cover the measurement range of Young’s modulus from 1 k Pa to 20 GPa using two AFM probes.This method broadens the measurement range of the Young’s modulus of a single probe to 4 orders of magnitude,which is 2 orders of magnitude higher than the traditional method.It can achieve high-efficiency,accurate and wide-range Young’s modulus measurement of materials.Using the advantages of non-resonant magnetic drive in liquid to carry out the research of dynamic viscoelasticity measurement of cells in a broad frequency range.The magnetic sphere was used as the probe tip to obtain dynamic viscoelasticity of cells by appling mechanical stimulation on them with small contact vibrations of multiple frequencies distributed in a broad frequency range.In addition,a single-frequency viscoelastic model,a multi-frequency structural damping model,and a dynamic model of the probe under multi-frequency excitation were constructed.Dynamic viscoelasticity of cells at different indentation depths in a broad frequency range(10 Hz～15 k Hz)is achieved,and the relationship between different parameters,indentation depth,and measurement frequency in the viscoelastic model is revealed.This helps to understand the mechanical properties of the whole cell from multiple dimensions.Through the construction of magnetic-driven AFM probe microgripper,research on the efficient measurement of micro-nano interface adhesion was carried out.An AFM probe microgripper integrating micromanipulation and adhesion measurement was developed,and a dynamic contact detection,grasping and release strategy for the probe microgripper was built.The precision of the force control of the microgripper can reach p N level,and it also realizes the rapid replacement of the probe tip.Combined with the AFM adhesion rapid measurement technology,the adhesion between the clamped object and the interface can be quickly mapped.The experimental results of batch measurement of adhesion between cellulose spheres and cellulose membranes verify the effectiveness and feasibility of the proposed method.In summary,this dissertation develops an AFM non-resonant magnetic-drive technology,a broad modulus range nanomechanical measurement method,a broad frequency range dynamic viscoelastic measurement method,and efficient measurement method of interface adhesion.In this dissertation,the existing magnetic-driven AFM technology that can only qualitatively measure the mechanical properties of materials is promoted to the quantitative level.These methods will provide new measurement approaches and platforms for characterizing micro/nanomechanical properties.They have important application prospects and scientific research values in the fields of developing new materials,studying biological structures,and creating micro/nanorobots.