Titanium Electrochemical Microstructuring Applied to Biological Model Surfaces

INTRODUCTION: Titanium and titanium alloys have attracted considerable interest in aerospace, chemical process and biomedical industry due to their biocompatibility, good mechanical properties and excellent corrosion resistance. The chemical stability of titanium results from the presence of a thin but stable surface oxide film, typically a few nanometer thick. In nonaqueous electrolytes containing perchloric or sulphuric acid, the oxide film is unstable and anodic polarization leads to titanium dissolution at high rate. Recently, a sulphuric acid based-methanol electrolyte has been developed for electrochemical polishing of titanium [1,2]. Best polishing was obtained in an electrolyte containing 3 M sulphuric acid for applied potentials above 8 V corresponding to mass-transport controlled dissolution conditions [2]. Using this electrolyte, well-defined topographies in the micrometer range were produced on bulk titanium by electrochemical micromachining through a patterned photoresist [3]. This method involves high-speed selective metal dissolution from unprotected areas of a photoresist-patterned work-piece that is made an anode in an electrolytic cell. Compared to chemical etching, electro-chemical dissolution offers higher rates and better control on a microand macro-scale of shape and surface texture of anodically dissolved materials. Biological performances of implantable titanium devices in medicine and dentistry have been shown to depend on their surface topography. This latter must be carefully controlled in the micro and nanometer range to achieve cell adhesion and differentiation [4]. Thus, through-mask electrochemical micromachining appears to be a useful method for the fabrication of well-defined surface structures on bulk titanium.