Metallic implants

There are, however, continuing difficulties for catalytic appHcations of ion implantation. One is possible corrosion of the substrate of the implanted or sputtered active layer this is the main factor in the long-term stabiHty of the catalyst. Ion implanted metals may be buried below the surface layer of the substrate and hence show no activity. Preparation of catalysts with high surface areas present problems for ion beam techniques. Although it is apparent that ion implantation is not suitable for the production of catalysts in a porous form, the results indicate its strong potential for the production and study of catalytic surfaces that caimot be fabricated by more conventional methods. 

Levine, D. L. and Staehle, R. W., Crevice Corrosion in Orthopaedic Implant Metals, Journal of Biomedical Materials Research, 11, 553 (1977)... 

A recoil-implanted metal atom (radioactive M) undergoes the following chemical reaction with a metal coordination compound in a film of catcher material ... 

Dymond AM, Kaechele LE, Jurist JM, et al. 1970. Brain tissue reactions to some chronically implanted metals. J Neurosurg 33 574-580. 

One way to overcome the sample homogeneity problem has been to develop standards by ion implantation [80-83]. Here, the concentration and distribution of the dopants can be controlled more accurately, thereby forming standards with better homogeneity. However, the results with semiconductors, have been much more reliable than with ion-implanted metal standards [82, 83]. 

Sinha, R. K., and Tuan, R. S., Regulation of human osteoblast integrin expression by orthopaedic implant metals. Bone 18, 451-457 (1996). 

Implantations of yttrium and cerium in 15 % Cr/4% A1 steel and aluminized coatings on nickel-based alloys did not improve the high-temperature oxidation resistance even though conventional yttrium alloy addition had an effect. The differences for the various substrates are attributed to different mechanisms of oxidation of the materials. The austenitic steel forms a protective oxide film and the oxidation proceeds by cation diffusion. Thus, the yttrium is able to remain in a position at the oxide/metal interface. The other materials exhibit oxides based on aluminum. In their growth anion diffusion is involved which means an oxide formation directly at the oxide/metal interface. The implanted metals may, therefore, be incorporated into the oxide and lost by oxide spalling. 

Pethica, J.B. Oliver, W.C. (1982) Ultra-Microhardness Tests on Ion-Implanted Metal Surfaces, Ion Implantation into Metals (Ashworth, V. et al, eds.) Pergamon, London, p. 373. 

Today, a typical process flow for advanced ICs consists of 300 to 500 steps, 30% of which are wafer cleaning steps." Many process steps during IC fabrication may introduce contamination, which must be cleaned before the next process step. For example, in processes such as steam oxidation, resist etching, and ion implantation, metallic contamination typically introduces a surface concentration of 10 to lO Vcm. The need for wafer cleaning can be separated into three areas (1) preparation of the wafer surfaces for oxidation, diffusion, deposition, and metallization (2) preparation for the application of photoresist and (3) removal of photoresist after the etching process." ... 

The same publication reports on nonlinear dependence between pitting potential of ion-implanted binary surface alloys of aluminum and zero points of oxides of implanting metals. 

In 1988, Sunderman reviewed the clinical and experimental evidence and appraised the carcinogenic hazards from implanted metal alloys containing Ni, Cr or Co. In the same report, the author provided general background information on epidemiological evidence that certain occupational and environmental exposures to metal compounds are associated with excess cancer risks in humans and in experimental animals. 

Williams DF (1981) Toxicology of implanted metals. In Williams DF, ed. Fundamental Aspects of Biocompatibility Vol II, pp. 1-10. CRC Press, Boca Raton, Florida. 

Jackson LW, Dennis GJ and Centeno JA (1998) Analytical determination of blood silicon inpatients with silicone breast implants. Metal Ions Biol 5 33-38. 

The biological response to metals can be improved by modifications to the surface composition of an implantable metal alloy. This follows from the work on bioactive glasses which, when implanted into the body, produce a modified surface that facilitates apatite precipitation (Hench 1998a). Various chemical enrichment treatments have been proposed to aid the precipitation of a carbonate apatite. 

Injection site tumors are induced by many nickel compounds that do not cause cancer in animals by other routes of exposure. In fact, most of tihe published literature on nickel carcinogenesis concerns injected or implanted metallic nickel or nickel compounds these data are of limited value in determining carcinogenic exposure levels for avian and terrestrial wildlife. The applicability of these studies to a recommendation for human workplace exposure is also questionable. Nevertheless, injection or implantation site sarcomas have... 

FoUstaedt, D. 1985. Metastable phase formation in ion-implanted metals. Nucl. Instrum. Methods. Phys. 

In order to fuUy exploit the scalability of DE actuators, it necessary to be able to pattern electrodes on the micro scale as well. Rosset el al have explored the use of ion implanted metal electrodes in PDMS [221-224]. Their results show that conductivity can be maintained for strains up to 175% and can remain conductive over 10 cycles at 30% strain. This is of particular importance for MEMS microfluidic devices where the DE micro-actuators could be used as micro-pumps. The ion-implanted films maintained high breakdown fields (>100 MV m ) while the Young s modulus increased by 50-200% depending on the dose. 

Scaffolds can be produced from a variety of materials, including metals, ceramics, and polymers. In dental and bone implants, metallic alloys are preferred [4, 5], while ceramics with good osteoconductivity have been used for bone tissue... 

Concerning inorganic or organic reactions, the primary corrosion products of the metallic implants are mainly responsible for the biocompatibility of the implanted metal because they may have, due to their large surface, an interaction with the tissue or with the body fluid. The metal is transported by a solution in the body fluid to the various organs where due to an enrichment of the metal an undesirable interaction may occur. 

Variola, F., Vetrone, F., Richer , L., Jedrzejowski, P., Yi, J.-H., Zalzal, S., Clair, S., Sarkissian, A., Perepichka, D.F., Wuest, J.D., Rosei, F., Nanci, A., 2009. Improving biocompatibility of implantable metals by nanoscale modification of surfaces an overview of strategies, fabrication methods and challenges. Small 5, 996—1006. 

In the medical device community, the surface of a material is extremely important because it is what is in contact with the body. For example, the components of implants may be plasma treated to make their surfaces more biocompatible, which reduces cell adhesion and the formation of fibrous tissue around the implant. Implantable metal devices are often passivated to make the device resistant to corrosion when subjected to the aqueous environment inside the body. 

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