How to weld a nickel-titanium alloy wire inside human blood vessels?

　　How to weld a nickel-titanium alloy wire inside human blood vessels?

　　Nickel-titanium alloy wires have become essential materials in interventional medicine and biomedical engineering. However, connecting nickel-titanium alloy wires with medical-grade stainless steel remains a significant challenge in the design and manufacturing of medical devices. Some medical device manufacturers have adopted methods such as physical crimping, fixation via sleeves, and adhesive bonding between the nickel-titanium alloy wire and stainless steel wire. Yet these approaches often lead to increased physical dimensions of the sleeve joints, compromising maneuverability, reducing connection strength, and causing unintended changes in material properties—making it difficult to meet the stringent requirements for clinical applications.

　　The role of nickel-titanium alloy wires in intravascular interventional procedures is to navigate through the vessel lumen, passing through channels, branches, and tortuous sections—sometimes even overcoming narrow areas—to reach the target site. They are used to guide catheters, microcatheters, and other interventional devices to the intended location or region. When guidewires selectively enter coronary arteries affected by coronary heart disease, tiny cerebral arteries within the skull, vascular malformations, or small feeding vessels, they play an irreplaceable guiding role.

　　From a performance standpoint, the ideal nickel-titanium alloy guidewire must exhibit excellent push-and-torque control. Additionally, given its small diameter, it should maintain its shape without significant deformation when navigating and advancing through curved blood vessels. As the guidewire is slender yet long, its tip must be easily guided into the vessel, effortlessly passing through curved segments or overcoming narrow constrictions. Moreover, since many small vessels have relatively weak walls, the microguidewire—despite its tiny diameter—must demonstrate maximum flexibility and superelasticity to minimize friction against the vessel wall and reduce the risk of potential damage to the vessel lining.

　　From the perspective of the guidewire's overall structure, functionality, and material selection, whether the guidewire is coated with a spring or made from a polymer material, its inner core must exhibit excellent flexibility at the tip. This ensures that the guidewire won't damage the vessel wall during passage through blood vessels. Additionally, the core should possess superelasticity, enabling it to resist deformation even after bending—and preventing it from reverting to its original shape when navigating through tightly coiled vascular segments. Once past these challenging areas, the guidewire can be straightened and stretched again thanks to its inherent superelastic properties.

　　Does the nickel-titanium alloy rope affect the human body?

　　Currently, from a medical perspective, nickel-titanium alloy is beneficial to the human body and should not pose any harm to health.

　　Nickel-based shape-memory alloys are a special chemical composition of nickel, specifically an atomic alloy of nickel and titanium containing about 50% nickel. Nickel is known to promote and enhance bonding, while the surface layer of titanium oxide acts as a protective barrier, giving nickel-titanium alloy wires excellent biocompatibility. The surface layers of TiXOy and TixNiOy effectively inhibit the release of nickel ions. Moreover, the greater the vibration generated by chewing or bruxism on the archwire, the more severe the potential damage to the tooth roots and periodontal tissues. Experimental results from various archwire damping tests reveal that stainless steel wires exhibit larger amplitudes compared to superelastic NiTi wires—yet the initial amplitude of superelastic NiTi archwires is only half that of stainless steel wires. These superior vibration-damping and shock-absorbing properties of NiTi wires are crucial for maintaining optimal dental health, whereas conventional wires like stainless steel tend to exacerbate root resorption.