Nitinol: From historical milestones to functional properties and biomedical applications

Abstract

Isoatomic NiTi alloy (Nitinol) has become an important biomaterial due to its unique characteristics, including shape memory effect, superelasticity, and high damping. Nitinol has been widely used in the biomedical field, including orthopedics, vascular stents, orthodontics, and other medical devices. However, there have been convicting views about the biocompatibility of Nitinol. Some studies have shown that Nitinol has extremely low cytotoxicity, indicating Nitinol has good biocompatibility. However, some studies have shown that the in-vivo corrosion resistance of Nitinol significantly decreases. This comprehensive paper discusses the historical developments of Nitinol, its biomedical applications, and its specific functional property. These render the suitability of Nitinol for such biomedical applications and provide insights into its in vivo and in vitro biocompatibility in the physiological environment and the antimicrobial strategies that can be applied to enhance its biocompatibility. Although 3D metal printing is still immature and Nitinol medical materials are difficult to be processed, Nitinol biomaterials have excellent potential and commercial value for 3D printing. However, there are still significant problems in the processing of Nitinol and improving its biocompatibility. With the deepening of research and continuous progress in surface modification and coating technology, a series of medical devices made from Nitinol are expected to be released soon.

Hoist-Based Shape Memory Alloy Actuator with Multiple Wires for High-Displacement Applications

“…The maximum contraction of SMA wires is generally within the range of 2% to 5% of their total length. The following equation, Equation (1), determines the augmentation displacement of the payload linearly with the number of nylon turns and the contraction of the SMA wires, where l is the length of the SMA wire, C is the determined percentage of contraction, and N is the number of threads in the hoist.…”

“…Smart materials have been studied to solve these problems due to their capacity for changing their physical or chemical properties in response to specific environmental stimuli. Shape memory alloys (SMAs) are a type of smart material that is commonly composed of nickel and titanium, and they are known for their exceptional mechanical and electrical properties, such as their heat and fatigue resistance [1]. SMAs exhibit two notable phenomena-the shape memory effect (SME) and superelasticity effect (SE)-which make them suitable for force generation and energy storage applications.…”

IR management of portal hypertension complications

“…Others have suggested under-dilation of the TIPS at the initial creation (ie, without the constraining stent, but balloon dilatation only to 6 or 7 mm). [23] However, given that the Viatorr is a self-expanding stent graft comprising of shape-memory Nitinol (nickel-titanium alloy) [24] scaffold, this strategy does not reliably prevent stent expansion to its nominal diameter over time. With the new Viatorr Cx now available, we place a constraining stent only when diameters below 8 mm are required.…”

Strategies for surface coatings of implantable cardiac medical devices

“…During the development of CMDs, multiple considerations must be made to select the proper materials: biocompatibility/hemocompatibility, mechanical properties, toxicity, infection, surface properties, degradability, and cost ( Alipour et al, 2022 ). Among the main considerations in the formulation of CMDs, biocompatibility is a fundamental aspect that must be acknowledged in CMDs for the short-term and long-term ( Ufukerbulut and Lazoglu, 2011 ).…”

“…Furthermore, in recent years nitinol has been the most widely used material for formulating of multiple cardiac devices ( Ufukerbulut and Lazoglu, 2011 ; Ahmed et al, 2020 ). NiTi has numerous benefits, such as extremely low cytotoxicity, excellent biocompatibility, memory effect, super elasticity, and high damping ( Pelton et al, 2004 ; Alipour et al, 2022 ; Nagaraja et al, 2022 ). Despite increasing patients’ life expectancy and quality of life, infections and biocompatibility issues in CMDs have emerged in recent years ( Timmis et al, 2022 ).…”