Etch-less microfabrication of structured TiO2 implant coatings on bulk titanium grade 23 by direct lithographic anodic oxidation

Abstract

Within this work, we demonstrate a method for the etch-less, additive microfabrication of TiO2 thin film layers on top of the medical implant material titanium grade 23. A combination of common UV-lithographic microfabrication and a subsequent anodic oxidation process allows the direct additive fabrication of microstructured oxide layers on top of the bulk base material without the use of any additional preparation or etching step. Titanium grade 23 samples were firstly prepared by grinding and polishing to achieve an adequate surface finish for UV lithography. Photoresist was applied to the samples and lithographically structured using line patterns with lateral sizes ranging from 1.5 up to 50 µm. The samples were then anodically oxidized within a H2SO4 containing electrolyte and the resist patterns could successfully be copied into the resulting oxide layers. The presented method allows cost-effective and fast microfabrication of structured oxide thin film layers while protecting the underlying bulk material from hazardous etching media, often containing hydrofluoric acid, enabling novel implant coating designs and fabrication concepts for future works.