Mechanical characterization of crosslinking effect in polydimethylsiloxane using nanoindentation

Abstract Polydimethylsiloxane (PDMS) is one of the widely-used silicone-based organic polymers. It can serve as a substrate to grow cells, mainly because of its controllable range of mechanical properties. Varying the degree of crosslinking in the polymer network allows tuning its mechanical properties in a range similar to living tissues. To study the PDMS stiffness effect on the growth and behavior of cells, it is of significant importance to explore the mechanical properties of a series of PDMS samples cured to different crosslink densities. In this paper, nanoindentation tests were conducted using spherical, Berkovich, cube corner and conical indenters to characterize PDMS mechanical properties. To interpret the nanoindentation data, the nano-JKR force curve method was successfully extended to include Berkovich, cube corner and conical indenters by conducting a numerical simulation in which the adhesive interactions are represented by an interaction potential and the surface deformations are coupled by using half-space Green's functions discretized on the surface.