Thickness-dependent mechanical properties of polydimethylsiloxane membranes

Polydimethylsiloxane (PDMS) has cross-linked network structures and its properties have been regarded as dimensionally independent. Here we demonstrate that both the mechanical strength and the Young's modulus of the PDMS membranes are thickness dependent and the transition from bulk behavior to dimension dependent is predicted to occur at a membrane thickness of about 200 mu m. The thickness-dependent phenomenon is attributed to shear stress during fabrication, which is proportional to the thickness-induced reorder of polymer chain coils to form stronger cross-linked networks.