Initial and adhesive contact between a diamond indenter and polydimethylsiloxane

Detailed observations for the initial and adhesive contact of polydimethylsiloxane indentations with sharp indenters are proposed and discussed in this study. In dry experiments, the load-depth results revealed an almost reversible feature, which indicated elastic deformation. Significant initial penetration depths, created during the finding surface process, were found. A power-law relationship was used to illustrate the initial portion of the loading curve and to evaluate the initial penetration depth for correcting depth measurements. An axisymmetrical indenter with a sticky boundary condition was applied to illustrate the results of dry experiments. When the load exceeded a specific value, both loading and unloading results showed an invariant slope. The analysis of the sticky indenter provided a reasonable explanation for the linear load-depth results. By correcting the initial penetration depth, the evaluated Young's modulus values, obtained from the indenters with different geometries and under different environments, were shown to be unique and accurate.