The investigation of anodic polarization characteristics of NiTi thin films for fabricating vascular stents using electrolytic photo etching technique

摘要

This research aimed to develop a process to micro machine vascular stents from NiTi thin films. The stent has been recognized as useful for minimally invasive medical applications. A non-traditional machining process called electrolytic photo etching was chosen in this research. This process involves photo resist processing and electrolytic etching, which is done by controlling the anodic polarization characteristics of NiTi thin films so as to prevent creating a passivation layer on them. In order to investigate the electrochemical characteristics of NiTi thin films quantitatively in the electrolyte of 5% sulphuric acid in methanol, the anodic polarization measurements at a series of constant anode potentials were conducted. The electrolyte temperature and electrode distance were also to be varied during the measurement. In order to optimize process parameters for electrolytic etching stents, such as electrolyte temperature, electrode distance and current density, the analysis of the correlation of anodic polarization behavior of NiTi thin film to its active, passive and transpassive characteristics in the electrolyte was performed.