Surface detection errors cause overestimation of the modulus in nanoindentation on soft materials.

The accuracy of mechanical properties from depth-sensing indentation, or nanoindentation, depends on the accuracy of the displacement measurement used to calculate these properties. Here, current nanoindentation techniques and analysis methods for accurate displacement measurements are reviewed. First, the ability of a commercial instrument to sense the surface of soft materials is examined. Second, methods of sample surface detection are reviewed. Finally, a case of overestimation of the elastic modulus of a compliant material using nanoindentation with incorrect displacement values is presented.