Nanoindentation method for determining the initial contact and adhesion characteristics of soft polydimethylsiloxane

In this paper, we present a method for determining the initial contact point and nanoindentation load-indentation depth characteristics for soft materials. The method is applied to the prediction of the load-indentation depth characteristics of polydimethylsiloxane. It involves the combined use of Johnson-Kendall-Roberts and Maugis-Dugdale adhesion theories and nonlinear least squares fitting in the determination of the initial contact point, the transition parameter, and the contact radius at zero contact load. The elastic modulus and the work of adhesion are also extracted from the load-indentation depth curves.