چكيده به لاتين
Atomic Force Microscope (AFM) has several applications such as topography and nanomanipulation (including cutting, stretching, movement and indentation). To accurately model the dynamical behavior of AFM, properties and components of AFM must appropriately be identified. Dimensions of the system as well as range of particle scale are significant parameters affecting the AFM performance. AFM is used to manipulate the particles which are in the range of micro or nano. In this thesis, the nanomanipulation of nanoparticles by using AFM is modeled with an improved approach. The dimensions of main AFM components, e.g. cantilever and tip, and target particles, are in micro and nano scales. Because of the difference between component scales, each part should be modeled employing an appropriate method. The appropriate approach for modeling of micro structures is continuum mechanics. However, since nanostructures are composed of discrete atoms, suitable method for modeling of these structures is molecular dynamic. Therefore, applicable solution for modeling this kind of structures is to utilize multi-scale approaches. Furthermore, since the AFM components are in micro scale, theories of the non-classical continuum mechanics must be used for more accurate modeling. Consequently, a three-dimensional multi-scale method based on the modified couple stress theory for modeling of nanomanipulation process is presented in this thesis.
First, the nanomanipulation structure is divide into two parts; Macro-Field (MF) and Nano-Field (NF). Then, the governing equations of cantilever (as the most significant part of MF) are derived using the modified coupled stress theory and the Kirchhoff plate model. By considering the effect of applied voltage on the frequency, the result shows the non-classical critical voltage (i.e. the voltage in which the natural frequency approaches to zero) is larger than the classical one in each thickness. Moreover, the NF (including the nanoparticle and its surrounding area that is in nano scale which are modeled using the molecular dynamics equations) and MF are then combined employing the multi-scale algorithm. After validating the model, Rectangular and dagger cantilevers are taken into account to obtain nanomanipulation results. The influence of two types of tip on the nanomanipulation results is also investigated. The obtained results show that the deformations of the AFM components in non-classic models are less than the one in the classical model. A comparison between rotation angle of nonclasscial and classical model in two microcantilever shows a reduction proportion of 1 to 10 in rotating angle. Using this model and considering the effect of size and shape, the nanomanipulation of carbon allotropes such as CTNs and fullerenes is carried out. The result shows the indentation depth which is created by spherical nanoparticle is about two times greater than the cylindrical nanoparticle and the nanomanipulation force of spherical geometry is about 5.5 times greater than cylindrical nanoparticle. In nanomanipulation, a nondestructive and successful process can be achieved by using nanocarrier. To achieve a nondestructive nanomanipulation process, carbon nanotube (CNT) is used as a nanocarrier. A set of nanomanipulations is performed for the free ssDNA and the ssDNA inside the nanocarrier on the golden, graphene and silicon substrates. The obtained results show that using the nanocarrier reduces the nanomanipulation force considerably. Force reduction is 75% for golden substrate, 50% for graphene and 80% for silicon substrate. Finally, to investigate the nanomanipulation in various environmental conditions such as a vacuum, aqueous and humid ambient, the fluid flow in the MF is assumed as the Couette and Creeping flows. The Electro-Based (ELBA) model, as a coarse grained model, is considered to model the ambient condition in the NF. The nanoparticle under the different conditions such as submerged, vacuum and various humidity is taken into account to study the nanomanipulation. The comparison of nanomanipulation force in different humidity percentages shows that the nanomanipulation force decreases as the humidity increases. The maximum nanomanipulation force occures in 0% humidity and the minimum nanomanipulation force occures in 100% humidity. The nanomanipulation force ratio in zero pecent humidity to 100% humidity is 6.
