Multi-scale mechanical characterization of a freestanding polymer film using indentation

A thin circular film is clamped at the periphery. An external mechanical force is applied to the film center via either a shaft with a spherical cap or a ball bearing with a specific weight. The deformed geometry allows the materials parameters of the film to be assessed for a wide range of length scales. Solid mechanics models are derived for a multi-scale deformation range as the film experiences (i) indentation or Hertzian contact, (ii) plate-bending, (iii) membrane-stretching, and (iv) large deformation. The method caters to ultrathin membranes where conventional macroscopic tensile tests might potentially damage the sample films. Thin film adhesion-delamination can also be characterized by the same set-up. Experiments were conducted for a range of polymer films.