Phase transformation and mechanical behaviors of vena cava filter modified by deposition of copper–titanium coating

In our previous study, a copper–titanium (Cu/Ti) coating was developed to enhance the blood compatibility and anti-endothelialization of NiTi vena cava filter. In the present study, the phase transformation and mechanical behaviors of the Cu/Ti-coated NiTi vena cava filters were further investigated. The filters were shaped to final dimensions by a three-step shape-setting process using different dimension moulds for each step. After each step of shape-setting process, the phase transformation and mechanical properties were examined by differential scanning calorimeter (DSC) method and tensile experiment, respectively. It was found that the austenite transformation finish temperature (Af) of Cu/Ti-coated filter increased first and then slightly decreased with the increase of aging time. The Af value of Cu/Ti-coated filter was higher than that of the pristine filter when the same shape-setting process was applied. Two phase transformation peaks could be observed on the heating curves of Cu/Ti coated samples when the aging time increased. Although on the stress–strain cycle curves there were no obvious differences between Cu/Ti-coated and the pristine filters when the same shape-setting process was applied, the values of upper yield plateau and lower yield plateau of both of the filters tended to decrease gradually with the increase of aging time. The results of the present study indicated that the fabrication of Cu/Ti coating on NiTi vena cava filter can improve the Af value and did not change its super-elasticity. It may be helpful for the development of novel biomedical devices, such as vena cava filter and vascular stent, where control of self-expansion and shape memory of implants would be preferable.