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Dynamic Modeling and Control of Atomic Force Microscope in Trolling Mode

Sajadi, Mohammad Reza | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50762 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Vosoughi, Gholamreza; Nejat Pishkenari, Hossein
  7. Abstract:
  8. Trolling mode atomic force microscope (TR-AFM) significantly reduces the hydrodynamic drag generated during operation in liquid environments. This is achieved by utilizing a long nanoneedle and keeping the cantilever out of liquid. In this research, a continuous mathematical model is developed to study TR-AFM dynamics near a sample submerged in the liquid. Effects of cantilever torsion, nanoneedle flexibility, and liquid-nanoneedle interactions are considered in the model. The finite element model of the TR-AFM resonator considering the effects of fluid and nanoneedle flexibility is presented in this research, for the first time. The model is verified by ABAQUS software. The effect of installation angle of the microbeam relative to the horizon and the effect of fluid on the system behavior are investigated. The present study develops a nonlinear model of the meniscus force exerted to the nanoneedle of TR-AFM and presents an analytical solution to the distributed-parameter model of TR-AFM resonator utilizing multiple time scales (MTS) method. Based on the developed analytical solution, the frequency-response curves of the resonator operation in air and liquid (for different penetration length of the nanoneedle) are obtained. The closed-form analytical solution and the frequency-response curves are validated by the comparison with both the finite element solution of the main partial differential equations and the experimental observations. This research develops a high-speed scanning technique to estimate the topography of various samples utilizing a two-degree-of-freedom model of TR-AFM
  9. Keywords:
  10. Trolling Mode Atomic Force Microscopy (AFM) ; Atomic Force Microscopy (AFM) ; Nonlinear Vibration ; Bending and Torsion Coupling ; Dynamic Modeling ; Nanoneedle

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