Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

Sivan, Shiril; Prima, Matthew Di; Weaver, Jason D.

doi:10.1007/s40830-017-0109-0

Cited by 5 publications

(2 citation statements)

References 22 publications

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“…Interestingly, the corrosion damage shown in Fig. 8 bears a strong resemblance to images from an unrelated study in our laboratory where corrosion damage was electrochemically induced during fatigue and similarly led to a reduced fatigue life (Ref 19). Here, as in the other study, corrosion pits were identified to be the site of initiation for a fatigue crack.…”

Section: Discussionsupporting

confidence: 59%

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Weaver

Gutierrez²,

Nagaraja

et al. 2017

J. of Materi Eng and Perform

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Processing of nitinol medical devices has evolved over the years as manufacturers have identified methods of reducing surface defects such as inclusions. One recent method proposes to soak nitinol medical devices in a 6% sodium hypochlorite (NaClO) solution as a means of identifying surface inclusions. Devices with surface inclusions could in theory then be removed from production because inclusions would interact with NaClO to form a visible black material on the nitinol surface. To understand the effects of an NaClO soak on performance, we compared as-received and NaClO-soaked nitinol wires with two different surface finishes (black oxide and electropolished). Pitting corrosion susceptibility was equivalent between the as-received and NaClO-soaked groups for both surface finishes. Nickel ion release increased in the NaClO-soaked group for black oxide nitinol, but was equivalent for electropolished nitinol. Fatigue testing revealed a lower fatigue life for NaClO-soaked black oxide nitinol at all alternating strains. With the exception of 0.83% alternating strain, NaClO-soaked and as-received electropolished nitinol had similar average fatigue life, but the NaClO-soaked group showed higher variability. NaClO-soaked electropolished nitinol had specimens with the lowest number of cycles to fracture for all alternating strains tested with the exception of the highest alternating strain 1.2%. The NaClO treatment identified only one specimen with surface inclusions and caused readily identifiable surface damage to the black oxide nitinol. Damage from the NaClO soak to electropolished nitinol surface also appears to have occurred and is likely the cause of the increased variability of the fatigue results. Overall, the NaClO soak appears to not lead to an improvement in nitinol performance and seems to be damaging to the nitinol surface in ways that may not be detectable with a simple visual inspection for black material on the nitinol surface.

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Section: Discussionsupporting

confidence: 59%

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

Weaver

Gutierrez²,

Nagaraja

et al. 2017

J. of Materi Eng and Perform

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“…Open Circuit Potential (OCP) of the guidewire surrogates was measured (using setup detailed in Sivan et al. 22 along with a NiTi bypass wire) to indirectly detect delamination or changes in the integrity of the coating on the surrogates.…”

Section: Methodsmentioning

confidence: 99%

Pre-clinical evaluation of surface coating performance in guidewire surrogates: Potential implications for coated interventional surgical devices

et al. 2019

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Purpose Polymer fragments have been identified from autopsy reports of patients who had at some point undergone intravascular procedures with medical devices (such as guidewires and catheters) with lubricious coatings. Coating separation on these devices may cause a range of adverse events, the most severe being patient death associated with undesired embolization of blood vessels by coating particles. The objective of the present study is to identify bench test methods for evaluation of hydrophobic and hydrophilic coatings to better understand the relationships between coating formulation and coating behavior, which in turn helps to determine safety and effectiveness of the coating on the device. Methods Hydrophilic or hydrophobic coatings were applied on prepared 304 V stainless steel guidewire surrogates. Coating integrity was assessed after exposing the surrogates to extended periods of soaking and rotary bend fatigue testing. Additionally, coating durability was evaluated by abrasion testing. Results Soaking tests showed deionized water can cause more changes to the microscopic appearance of the coating on the guidewire surrogates as compared to 0.9% saline at both room temperature and 37°C; however, soaking tests in either medium did not alter coating integrity after 11 hours. Rotary bend fatigue, which subjects the coatings to both tension and compression, did not affect coating integrity on the guidewire surrogates after three hours. The pad material used in abrasion testing can lead to markedly different performance predictions. Conclusion Soaking, bend fatigue test, and abrasion tests can provide valuable information on coating performance. Coating integrity and durability were affected during abrasion testing, a test method that can provide more useful information for evaluating bench coating performance. It remains to correlate these findings with clinical performance, but emphasis should be placed on comprehensive characterization. Further investigation is needed by multidisciplinary stakeholders: materials scientists, engineers, and clinicians, to properly inform next steps.

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