CMP as a Nano-Structuring Method for Titanium Based Bio-Implants
Authors: Basim Gul Bahar , Sur Debashish , Beers Kimberly , Erwin Nina , Cicalese Jacqueline 
Published: July 2021

Nano-scale modification of macro-scale 3-dimensional implantable devices is gaining more attention as the cell attachment/detachment mechanisms at the bio-interfaces are profoundly affected by the nanoscale interfacial interactions [1]. Titanium based biomaterials are widely used for dental prostheses, orthopedic devices and cardiac pacemakers. Titanium and its alloys are most favored for hard tissue replacement due to their excellent mechanical properties and surface characteristics promoting biocompatibility due to spontaneous formation of a thick oxide layer in the presence of an oxidizer. This study focuses on the development of a three dimensional chemical mechanical nano-structuring (CMNS) process to induce smoothness or controlled nano-roughness on the bio-implant surfaces, particularly for an application on the dental implants. CMNS is an extension of the chemical mechanical polishing process. CMP is utilized in microelectronics manufacturing for planarizing the wafer surfaces to enable photolithography and multilayer metallization. In biomaterials applications, it has been shown that the same approach can be utilized to induce controlled surface nano-structure on 3-D implants to promote or demote cell attachment [2]. By tuning the polishing slurry particle size, solids loading and the chemical composition, both the chemical nature and the surface topography can be modified to make the surface very smooth or rough at nano-scale. This new technique helps produce implant surfaces that are cleaned from potentially contaminated surface layers by removing a nano-scale top layer while simultaneously creating a protective oxide film on the surface to limit any further contamination to minimize risk of infection [3]. As a synergistic method of nano-structuring on the implant surfaces, CMNS also modifies the mechanical properties on the implant surfaces and makes the titanium surface more adaptable for the bio-compatible coatings as well as the cells and tissue growth as demonstrated by the mechanical, electrochemical and biological evaluations. The ability of manipulating the surface nanostructure is also essential to understand the fibroblast and osteoblast cell attachment/detachment mechanisms on the implant surfaces to enable functionality of the implants whether the biocompatibility is a function of the cell attachment such as in the dental or prosthetic implants or limited attachment is needed for the functionality such as for the cardiac valves.

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