Atomic force microscopy for university students: applications in biomaterials

Abstract

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.

Hertz model or Oliver & Pharr analysis? Tutorial regarding AFM nanoindentation experiments on biological samples

“…AFM nanoindentation experiments on biological samples 2.1.1. Loading and unloading curves In a typical AFM nanoindentation experiment the AFM tip indents the sample of interest and a loaddisplacement curve is recorded [9,12]. The same procedure is also performed on a hard reference sample [9,12].…”

“…Loading and unloading curves In a typical AFM nanoindentation experiment the AFM tip indents the sample of interest and a loaddisplacement curve is recorded [9,12]. The same procedure is also performed on a hard reference sample [9,12]. As a result, the indentation values are calculated by the difference in the piezo-displacement between the hard and the soft sample for the same applied load [9].…”

“…Atomic Force Microscopy nanoindentation is a powerful technique for the characterization of biological samples at the nanoscale [1][2][3][4][5][6][7][8][9]. The data processing is usually performed using basic models arising from the contact mechanics theory [7,9]. If the sample that is being tested can be characterized as an elastic half space, the Young's modulus of the sample can be calculated using the Hertz model or the Oliver & Pharr analysis [7,9,10].…”

“…The data processing is usually performed using basic models arising from the contact mechanics theory [7,9]. If the sample that is being tested can be characterized as an elastic half space, the Young's modulus of the sample can be calculated using the Hertz model or the Oliver & Pharr analysis [7,9,10]. Despite the fact that these techniques are based on the same theoretical tools, there are significant differences regarding the data processing [7,9].…”

“…If the sample that is being tested can be characterized as an elastic half space, the Young's modulus of the sample can be calculated using the Hertz model or the Oliver & Pharr analysis [7,9,10]. Despite the fact that these techniques are based on the same theoretical tools, there are significant differences regarding the data processing [7,9]. However, if the biological sample can be considered as homogeneous and isotropic the two techniques should theoretically provide the same results [7,10].…”