Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Area of Science:

• Biomaterials Science
• Materials Engineering
• Medical Device Manufacturing

Background:

• Nitinol (nickel-titanium) is a common alloy in medical devices.
• Surface inclusions are defects that can compromise device performance.
• Manufacturers seek methods to identify and mitigate surface defects in nitinol.

Purpose of the Study:

• To evaluate the impact of a 6% sodium hypochlorite (NaClO) soak on nitinol medical device performance.
• To assess if NaClO soaks effectively identify surface inclusions without negatively affecting material properties.

Main Methods:

• Comparison of as-received and NaClO-soaked nitinol wires with black oxide and electropolished finishes.
• Pitting corrosion susceptibility testing.
• Nickel ion release measurements.
• Fatigue testing at various alternating strains.

Main Results:

• NaClO soak did not alter pitting corrosion susceptibility.
• Nickel ion release increased for black oxide nitinol but not electropolished nitinol.
• Fatigue life decreased for NaClO-soaked black oxide nitinol and showed increased variability for electropolished nitinol.
• NaClO treatment identified only one inclusion and caused visible surface damage.

Conclusions:

• The NaClO soak is not an effective method for identifying nitinol surface inclusions.
• The NaClO treatment can damage nitinol surfaces, potentially compromising device performance.
• The observed damage may not be apparent through simple visual inspection for black material.