Nitinol: The game‑changing alloy revolutionizing medical devices

Main image: Braiding is one of the core capabilities of Alleima. Credit: Alleima

Nitinol’s unique characteristics stem from its nickel-titanium composition. Its super-elasticity allows it to return to its original shape after deformation, which is crucial for devices like stents, guidewires or retrieval baskets. Thermal shape memory enables it to revert to a pre-defined shape when heated, which is useful for surgical instruments. Despite nickel’s toxicity, nitinol is biocompatible due to its titanium oxide layer.

Lumpectomy surgeries are less invasive, removing less breast tissue and leaving minimum scarring. The U.S. National Institutes of Health released a statement back in 1990 stating that a lumpectomy followed by radiation was preferred over mastectomy to treat early-stage breast cancer, and current studies indicate that this is still the case.

Nitinol’s super elasticity is pivotal in minimally invasive surgeries. Retrieval baskets are used to remove kidney stones or other foreign obstacles in the body. In vascular surgery, nitinol stents can be inserted in a compact form and then expanded inside the body, supporting blood vessels. Thanks to their flexibility and resilience, nitinol guidewires, used in endovascular procedures, navigate the body’s pathways without damaging vessel walls. That is also why nitinol is a very interesting material to use in the soft surgical robotics of the future.

“They are generally twisted wires, with two different twisting patterns – one is tighter than the other. That functions as a cue for the doctors when they are inserting it into the breast tissue as to how far it needs to go.”

Nitinol’s thermal shape memory offers a sustainable option for reusable medical tools in sterile environments. While most disposable nitinol devices leverage super-elasticity, thermal shape memory is increasingly used in instruments requiring consistent performance over multiple uses. The devices are deformed during use for patient personalization and then returned to their original shape during sterilization, maintaining their precision and functionality for repeated use. However, the complexity of sterilizing smaller, intricate devices has led to a rise in demand for disposable nitinol instruments despite their higher cost.

Nitinol’s biocompatibility is crucial for its medical applications. It resists corrosion and has a titanium oxide layer that prevents nickel ion release, reducing the risk of toxic reactions. This makes nitinol safe for long-term implants like cardiovascular stents and orthopedic devices.