Self-assembling (nano-)wrinkling topography formation in low-temperature vacuum deposition on soft polymer surfaces

Nano-topography formation on material surfaces gains increasing interest in sensor, biomedical, optical, tribological applications by the wide options of introducing functionalities to the surface. While top-down structuring processes are not useable for large surfaces, bottom-up techniques, utilizing even material properties for targeted nanostructure formation control, become highly valuable. Self-assembling, fractal-like nano- and microtopography formed by bottom-up processes (physical vapor deposition techniques, magnetron sputtering, pulsed laser deposition) on polymers are presented in this work. Wrinkling effects are due to high stresses in the deposited thin films of different inorganic coating materials - titanium and titanium nitride in the current work - with high adhesion on the polymer substrates (polycarbonate, polyimide, polyamide, thermoplastic polyurethane). The feature size of the nano-hills and vermicular-like structures in the size between 10 nm and 100 μm distance and up to 300 nm height is controlled by the mechanical properties in the formed compound material.