Effect of tip geometry of atomic force microscope on mechanical responses of bovine articular cartilage and agarose gel

The objective of this study is to investigate the effect of different Atomic Force Microscope (AFM) tip geometries (sharp-conical and spherical tips) on the microscale Young's modulus of bovine articular cartilage and agarose gel that is calculated by the method of the average point-wise modulus. The measurements of the microscale Young's moduli of 3% agarose gel under a conical AFM tip (20.9±4.9 kPa) and under a spherical AFM tip (17.5±3.0 kPa), averaged over an indentation depth of 600 nm, were comparable. However, the microscale Young's moduli of articular cartilage, as measured with a conical AFM tip (116.9±62.9 kPa), were significantly higher than the corresponding values under a spherical AFM tip (30.9±14.3 kPa). The results of the current study suggest that the AFM tip geometry affects the microscale measurements of the mechanical properties on the surfaces of biological materials. The findings of the study can help to elucidate more accurately the microscale mechanical properties on the surface layers of diverse biological materials including tissue-engineered cartilages with different material characteristics. © KSPE and Springer 2010.