A diamond knife is a very sharp knife whose edge is made from diamond, invented by Humberto Fernández Morán in 1955. Diamond knives are used for medical and scientific applications where an extremely sharp and long-lasting edge is essential. The knives are very expensive to initially purchase, depending on the quality and size of the knife; in addition the knives must be professionally sharpened as the edge dulls.
In particular they are the main tool, together with the microscope, for the radial keratotomy invented by Svyatoslav Fyodorov to correct myopia and for the Mini Asymmetric Radial Keratotomy (M.A.R.K.), invented by Marco Abbondanza to correct astigmatism and cure the first and second stages of keratoconus.
When the development of ultramicrotomy evolved, it was also determined that metal microtome knives or razor blades were too dull to cut ultrathin sections. The metal knives were soft and fragile and would lose their cutting edges when thin sections were required for transmission electron microscopy. In 1950, Latta and Hartmann discovered that the edge of broken glass could be used to cut thin sections of specimen. Glass knives are very popular in ultramicrotomy for trimming specimen blocks and cutting thin and ultrathin sections. A skilled operator can cut a small number of ultrathin sections with a glass knife, while the same operator can use a diamond knife to cut thousands of sections on one area of knife. Some hard specimens, such as bone, plants, thick-walled spores metals and ceramics are difficult to cut, even with a good glass knife, because the edge dulls too quickly. Humberto Fernández-Morán discovered that a gem-quality diamond could be used to fabricate a more durable knife for use in the ultramicrotomy; diamond was a logical material to use since it was the hardest known material at the time.
Diamond knives are both delicate and expensive, usually costing several thousand dollars. Natural gemstones used to produce diamond knives are usually pale yellow, of regular crystal structure and of the greatest possible purity. The grinding process usually reduces the stones to 50% of their original weight. The diamond blade is then mounted into a soft metal shaft (Wood's metal) and finally polished to a very sharp edge. The knife's edge is extremely sharp and free of imperfections, which helps to produce ultrathin sections of very regular thickness to get views of specimens at high magnifications with the transmission electron microscope (TEM). The shaft containing the final edge is then mounted in a metal trough, or "boat", and cemented, usually with an epoxy plastic. Diamond knives are also used for specimen preparation for Atomic Force Microscope.
There are many styles and types of diamond knives. For the most part, they can be made for use dry or wet. Blade angles of diamond knives vary from 35 to 60 degrees. The smaller angles knives are used for finer cutting, but these knives are prone to damage. Wide angle knives have better life expectancy.
|This article lacks ISBNs for the books listed in it. (June 2012)|
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