Oxide surfaces with tunable stiffness

An important challenge of modern materials science and nanoscience is to develop ways to alter the mechanical properties of an interface in a controlled fashion. Doing this while preserving the bulk properties of a material and maintaining a fixed chemical composition and reactivity of the interface is particularly attractive. In this work, the creation of substrates with tunable stiffness has been achieved by coating a soft polymer with an adherent, crack-free oxide overlayer whose thickness is varied from 8 to 70 nm. Specifically, amorphous titania with controlled, variable, thickness was deposited on polydimethylsiloxane (PDMS), and the surface mechanical properties were characterized using atomic force microscope (AFM)-based nanoindentation. The force/deformation curves can be quantitatively reproduced using a finite element analysis (FEA) modeling protocol. The FEA modeling facilitates predictability and enables the design of surfaces with independently customized chemical and mechanical properties.