Advances in the mechanical characterization of soft materials by nanoindentation

The emergence of nanoscience has spurred the demand for technologies capable of probing physical phenomena at resolutions down to the atomic length scale. Under this initiative, recent advances in instrumented nanoindentation have made the atomic force microscope and the depth-sensing nanoindenter practical tools in studying the local material properties of a broad array of solid surfaces at microscopic and sub-micron length scales. High resolution capability is especially important in the probing of biological samples, which are typically very inhomogeneous. In this paper, the current state 334 David C. Lin et al. of the field as it pertains to the mechanical characterization of soft solids is reviewed. The spectrum of contact mechanics theories based on linear elasticity and their application to nanoindentation data are presented, followed by a summary of data analysis techniques. The authors' comprehensive algorithm for the automated processing of large collections of data is highlighted and examples are shown to illustrate the robustness of the method. Limitations of the method and other considerations for successful application of nanoindentation to soft materials are discussed.