טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAginsky Ziv
SubjectNonlinear Dynamics and Stability of Microbeams for Scanning
Probe Microscopy in a Liquid Environment
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Oded Gottlieb
Full Thesis textFull thesis text - English Version


Abstract

The Atomic Force Microscope (AFM) maps surface samples down to subatomic resolution by indirect estimation of atomic interaction forces. This is obtained by measuring a van der Waals like atomic interaction between a sample and a vibrating microcantilever, which has a sharp tip at its free end. Recently there has been a growing interest in atomic force microscopy immersed in liquids as a result of the need to map chemical and in-vitro biological systems. A microcantilever immersed in a fluid is strongly affected by inertial and damping effects. The dynamic behavior of the cantilever crucially depends on the fluid in which the beam is immersed and the proximity to the sample surface. In a fluid environment, the resonance frequency is much lower than that obtained in air and its response curve is broad. Furthermore, the quality factors are reduced by several orders. Improvement of imaging and high quality quantitative force measurements requires a better understanding of the system dynamic interaction. Thus, investigation of accurate AFM models in a fluid environment is needed. This research includes derivation and theoretical analyses of a continuous model for a vibrating AFM that consistently incorporates nonlinear atomic interaction with the sample and the fluid-structure interaction with an aqueous environment. The analysis includes both multiple-scales asymptotics of weakly nonlinear system response and numerical analysis of strongly nonlinear dynamics.  Results portray system response near primary, secondary and internal resonances of the immersed AFM system in proximity and far from the sample’s surface.