The application of the AFM nanoindentation procedure in order to determine the Young’s modulus values of specific nanoregions, results in many uncertainties, especially when biological samples are tested. This fact is due mainly to significant errors concerning the Young’s modulus calculation because physical parameters such as the spring constant of the cantilever and the exact shape and size of the tip provide uncertainties. Thus, the objective of this paper was to introduce a more accurate and simple approach of the nanoindentation technique by introducing the relative differences of Young’s modulus values. The new approach can be applied in measurements where the influence of a controlled external factor on a specific nanoregion is tested or variations in the mechanical properties of heterogeneous materials are investigated. The analysis was based on the general mathematical analysis which is used in the indentation procedure for the characterization of biological samples. The major advantage of the new technique is that it depends only on the cantilever’s deflection – displacement curves which can be obtained with great accuracy. In addition, in order to provide full insight in the new technique, the mechanical heterogeneity of collagen was examined. As a conclusion, when a sample is tested under the influence of a controlled external factor, or when inhomogeneous samples are tested, the determination of the percentage variations of the Young’s modulus is the most accurate parameter.
Keywords: AFM, biomaterials, cantilever’s spring constant, mechanical nano-characterization, nanoindentation, percentage
differences of Young’s modulus, Young’s modulus.
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