The surface topography of an implant is one of the factors determining the success of its osseointegration. Since the surface of bone tissue exhibits nano-sized topography it is of interest to fabricate similar bio-inspired topographies on implant surfaces and to understand the interaction between these surfaces and their biological surroundings. For systematic in vitro/in vivo investigation it is desirable to work with surface topography features with tuneable dimensions.

We have used a mask anodization method to create tuneable nano-sized dot features on polished titanium sheets to be used for evaluation of nano-topography effects on osteoblast-like cells in vitro. By depositing a layer of aluminium onto polished titanium samples and subsequently anodizing the aluminium, a self-organised porous alumina mask was created on top of the titanium substrate. Further anodization transferred the mask pattern to the titanium substrate resulting in dot-like nano-sized titanium oxide features beneath the alumina pores. The porous alumina mask was finally removed in a selective chemical etch to reveal the titania features. The diameters, centre-centre distances and heights of the titania dots could be varied between ~20 nm - 100 nm by changing the anodization parameters. An oxalic acid electrolyte was used for all anodizations to ensure equivalent surface chemistry. The dot size range could be further increased by using other electrolytes. The anodized surfaces have been characterized using SEM, AFM and TEM.

The formation process of the titania dots changed depending on the mounting of the aluminium/titanium samples. When titanium was exposed to the electrolyte during anodization, the titania structures were formed on top of the alumina pore bottoms and were therefore etched off the surface during the selective chemical etch of the alumina mask. Possible formation mechanisms have been discussed.

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