Abstract
Nitinol shape memory alloys (SMAs) are attracting considerable attention as core materials for medical guidewires because of their excellent flexibility and shape retention. However, since Nitinol guidewires possess low rigidity, the pushability and torquability of the guidewires are insufficient. On the other hand, although stainless steel guidewires have high pushability, plastic deformation easily occurs. We have developed a new class of superelastic guidewires with functionally graded properties from the tip to the end by using new SMA core materials such as Cu-Al-Mn-based or Ti-Mo-Sn SMAs. The tip portion of the guidewire shows excellent superelasticity (SE), while the body portion possesses high rigidity. These functionally graded characteristics can be realized by microstructural control. These guidewires show excellent pushability and torquability and are considerably easier to handle than conventional guidewires. Moreover, a metallic catheter using a Ni-free Ti-based SMA with high biocompatibility is introduced.
