Submicron-patterning of bulk titanium by nanoimprint lithography and reactive ion etching

摘要

Nanopatterns on titanium may enhance endosseous implant biofunctionality. To enable biological studies to prove this hypothesis, we developed a scalable method of fabricating nanogrooved titanium substrates. We defined nanogrooves by nanoimprint lithography (NIL) and a subsequent pattern transfer to the surface of ASTM grade 2 bulk titanium applying a soft-mask for chlorine-based reactive ion etching (RIE). With respect to direct write lithographic techniques the method introduced here is fast and capable of delivering uniformly patterned areas of at least 4cm ~2. A dedicated silicon nanostamp process has been designed to generate the required thickness of the soft-mask for the NILRIE pattern transfer. Stamps with pitch sizes from 1000nm down to 300nm were fabricated using laser interference lithography (LIL) and deep cryogenic silicon RIE. Although silicon nanomachining was proven to produce smaller pitch sizes of 200nm and 150nm respectively, successful pattern transfer to titanium was only possible down to a pitch of 300nm. Hence, the smallest nanogrooves have a width of 140nm. An x-ray photoelectron spectroscopy study showed that only very few contaminations arise from the fabrication process and a cytotoxicity assay on the nanopatterned surfaces confirmed that the obtained nanogrooved titanium specimens are suitable for in vivo studies in implantology research.