جستجوی مقالات مرتبط با کلیدواژه « Atomic Force Microscope » در نشریات گروه « علوم پایه »

The Atomic Force Microscope (AFM) is a powerful tool for studying the properties and structures of materials at the nanometer scale. Unlike most surface analysis methods, it has no restrictions on surface types or their environment. This versatility allows AFM to investigate a wide range of materials, including conductive, insulating, soft, hard, cohesive, powdered, biological, organic, and inorganic. As such, it finds applications in diverse scientific fields such as chemistry, surface chemistry, polymer science, physics, molecular engineering, semiconductor science, biology, and medicine. Beyond its ability to image surfaces, AFM can also measure mechanical properties like Young's modulus. Young's modulus, also known as the modulus of elasticity (E), is defined as the ratio of stress to strain in the elastic region. This value reflects the stiffness of a material and changes with temperature. This paper explores the application of AFM in measuring Young's modulus across various scientific disciplines.

During past decade the AFM based nanomanipulation has been focus of attention as the promising nano fabrication approach. The main challenge in this process is the real-time monitoring. Consequently, the dynamic models have been proposed as a solution to the existing challenge. In the modeling approach the magnitudes of the forces are proportional to the stiffness coefficients of cantilevers. The precise calculation of these coefficients has been introduced in numerous works. The proposed stiffness coefficients for the V-shaped cantilevers fail to present in all commercial cantilever geometry. The geometrical deviation has a considerable impact on the magnitude of stiffness coefficients. Therefore, in this paper the existing model has been modified to include the commercial cantilever and take into account the effect of geometry variation. FEM simulation has been used to investigate the effect of geometry change and the results of these simulations have been exerted to the model which resulted in proposed comprehensive model. The proposed new stiffness model covers a wide range of commercial V-shape cantilevers and makes the process more practical.

A relationship based on the modified couple stress theory is developed to investigate the flexural sensitivity of an atomic force microscope (AFM) with assembled cantilever probe (ACP). This ACP comprises a horizontal cantilever, two vertical extensions and two tips located at the free ends of the extensions which form a caliper. An approximate solution to the flexural vibration problem is obtained using the Rayleigh–Ritz method. The results show that the sensitivities of AFM ACP obtained by the modified couple stress theory are smaller than those evaluated by the classical beam theory at the lower contact stiffness. The results also indicate that the flexural sensitivities of the proposed ACP are strong size dependant when the thickness of the cantilever is close to the material length scale, especially at lower contact stiffness. Furthermore, the greatest flexural modal sensitivity occurs at a small contact stiffness of the system, in which the ratio of the cantilever thickness to the material length scale and the distance between the vertical extensions are also small. In this situation, the distance between the vertical extensions and the clamped end of the cantilever and also the vertical extensions lengths are large. The results reveal that the sensitivity of the right sidewall tip is higher than that of the left one.

The resonant frequency and sensitivity of an atomic force microscope (AFM) cantilever with assembled cantilever probe (ACP) have been analyzed and a closed-form expression for the sensitivity of vibration modes has been obtained. The proposed ACP comprises an inclined cantilever and extension, and a tip located at the free end of the extension, which makes the AFM capable of topography at sidewalls of microstructures. Because the extension is not exactly located at one end of the cantilever, the cantilever is modeled as two beams. In this study, the effects of the interaction stiffness and damping, and also some geometrical parameters of the cantilever on the resonant frequencies and sensitivities are investigated. Afterwards, the influence of the interaction stiffness and damping, and the geometrical parameters such as the angles of the cantilever and extension, the connection position of the extension and the ratio of the extension length to the cantilever length on the sensitivity and resonant frequency are investigated. The results show that the greatest flexural modal sensitivity occurs at a small contact stiffness of the system, when the connection position and damping are also small. The results also indicate that at low values of contact stiffness, an increase in the cantilever slope or a decrease in the angle between the cantilever and extension can rise the resonant frequency while reduces the sensitivity.

Nanotechnology involves the ability to see and control individual atoms and molecules which are about 100 nanometer or smaller. One of the major tools used in this field is atomic force microscopy which uses a wealth of techniques to measure the topography and investigates the surface forces in nanoscale. Friction force is the representation of the surface interaction between two surfaces and surface topology. In order to have more precise nano-manipulation, friction models must be developed. In this study a sensitivity analysis has been conducted for nano-manipulation of nanoparticles toward dimensional and environmental parameters based on Coulomb and Hurtado and Kim (HK) friction models using Sobol method. Previously graphical sensitivity analysis has been used for this target in which the percentage of importance of parameters is not taken into account. But in Sobol method as a statistical model this problem is solved. Results show that cantilever thickness is the most effective dimensional parameter on critical force value while cantilever length and width are of less importance. Environmental parameters such as cantilever elasticity modulus, substrate velocity and adhesion, respectively, take next orders.