Elasticity of Cartilage Measured by Large Strain, Non-hertzian Afm Nanoindentation

INTRODUCTION The raster scanning and nanoindentation capabilities of the AFM are exploited in force spectroscopy, a valuable quantitative technique for mapping the elastic properties of materials down to nanometer resolution. When the probe is of well-defined geometry and the indentation behavior can be represented by established contact mechanics models, the force maps can be transformed to elastic modulus maps to facilitate comparison. This is especially important in biological specimens, where sample-to-sample variability is usually high. At relatively small strains, gels and other materials that exhibit rubber elasticity can be assumed to be linear elastic and the indentation mechanics modeled using the generalized Hertzian force-indentation (F vs. δ) relationship [1-2]: