Atomic Force Microscopy Characterization of Electrochemically Polished Nickel-Titanium Memory Alloy
Authors: Abdel-Fattah Tarek M 
Published: February 2024

Atomic force microscopy (AFM) is a powerful characterization technique used for monitoring metals or metal alloys surfaces changes [1-14]. AFM works by using a small probe, typically with a sharp tip, to scan the surface of a sample. As the probe moves over the surface, it measures the height and other properties of the surface topography, allowing for detailed analysis of the surface characteristics. Using AFM, it is possible to obtain high-resolution images in 2-dimintinal (2-D) or 3-dimintinal (3-D), allowing for detailed analysis of the surface morphology, roughness, and other properties. AFM can also be used to measure surface features, such as the height and depth of surface defects, or the thickness of surface coatings.

Smooth surfaces of metals or metal alloys are needed for many biomedical applications such as implants and stents. Electrochemical polishing (EP) is a process used to smooth and improve the surface finish of metals or alloys by selectively removing surface roughness using an optimum electric current. The resulting surface can have a highly polished and uniform finish. In this study, AFM is used to monitor the surface changed before and after EP of memory alloy (Nickel-Titanium, Ni-Ti Alloy). AFM image of a Ni-Ti Alloy’s surface is polished using a current density ranging from 0 to 0.147 A/cm2, which shows a highly polished surface after for 15 minutes. Surface roughness of the Ni-Ti alloy in ionic liquid as an acid free EP resulted in surface roughness significantly is reduced from 64 nm (before EP) to 11 nm without significantly altering the alloy elemental composition. This study provides an electrochemical acid free EP method to effectively control the relative smoothness of Ni-Ti implants at the nanoscale (less than 12 nm) which could offer many potential biomedical applications including controlling cell interactions with Ni-Ti alloy at bio-interfaces. Overall, AFM is a powerful tool for characterizing metal surfaces after electrochemical polishing, providing detailed information about the surface morphology and chemical composition that can be useful for a range of applications, from materials science research to quality control in manufacturing.

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