Atomic force microscopy for university students: applications in biomaterials

Atomic Force Microscopy (AFM) is a powerful tool regarding the investigation of the structural and the mechanical properties of a wide range of materials including biomaterials. It provides the ability to acquire high resolution images of biomaterials in nanoscale. In addition, it provides information about the response of specific areas under controlled applied force which leads to the mechanical characterization of the sample in nanoscale. The broad band of information provided by AFM have been established it as a complete scientific instrument with tremendous impact in modern research activity. In this paper, a general overview of the basic operation and functions of AFM is presented for applications in biomaterials. The basic operation is explained in detail with focus on the real interactions which are taking place in nanoscale during imaging. Furthermore, its ability to provide the mechanical characterization (force curves) of specific areas in nanoscale is presented. The basic models of applied mechanics which are used for the processing of the data obtained by force curves are presented. In conclusion, a general overview of the Atomic Force Microscopy for biophysics applications is provided which will contribute to the complete presentation of the instrument for university students and young researchers

Calculating the Duration of Impact When a Solid Sphere Collides on a Flat Rigid Wall

Calculating the duration of a motion when the applied net force on the moving body changes with time is usually a challenging task. In most cases, the only example of the duration of a motion when the acceleration is not constant presented to introductory physics students worldwide is the example of harmonic motion. A discussion with respect to the calculation of the duration of motion in more complicated cases is usually avoided due to its mathematical complexity. However, in this paper, a new simplified yet accurate approach is presented for the calculation of the duration of impact when a solid sphere collides on a flat rigid wall. The analysis is based on the calculation of the average stiffness of the sphere. It is important to mention that the percentage difference between the simplified approach and the rigorous mathematical analysis was calculated to be only 2.5%. © 2021 Author(s)