Ultramicrotomy is a method for cutting specimens into extremely thin slices, called ultra-thin sections, that can be studied and documented at different magnifications in an electron microscope such as a transmission electron microscope (TEM). It is used mostly for biological specimens, but sections of plastics and soft metals can also be prepared. For example, recently ultramicrotomy was used to make 2D material devices and use it for DNA sensing. The biological sections must be very thin because the 50 to 125 kV electrons of the standard electron microscope cannot pass through biologica
Ultramicrotomy is a method for cutting specimens into extremely thin slices, called ultra-thin sections, that can be studied and documented at different magnifications in an electron microscope such as a transmission electron microscope (TEM). It is used mostly for biological specimens, but sections of plastics and soft metals can also be prepared. For example, recently ultramicrotomy was used to make 2D material devices and use it for DNA sensing. The biological sections must be very thin because the 50 to 125 kV electrons of the standard electron microscope cannot pass through biological material much thicker than 150 nm. For best resolutions, sections should be from 30 to 60 nm. This is roughly the equivalent to splitting a 0.1 mm-thick human hair into 2,000 slices along its diameter, or cutting a single red blood cell into 100 slices.
==Ultramicrotomy process== Ultra-thin sections of specimens are cut using a specialized instrument called an "ultramicrotome". The ultramicrotome is fitted with either a diamond knife, for most biological ultra-thin sectioning, or a glass knife, often used for initial cuts. There are numerous other pieces of equipment involved in the ultramicrotomy process. Before selecting an area of the specimen block to be ultra-thin sectioned, the technician examines semithin or "thick" sections range from 0.5 to 2μm. These thick sections are also known as survey sections and are viewed under a light microscope to determine whether the right area of the specimen is in a position for thin sectioning. "Ultra-thin" sections from 50 to 100 nm thick are able to be viewed in the TEM. thumb|Low magnification of an ultra-thin section (length = 0.5 mm) of a megaspore of Salvinia cucullata (intermediate lens micrograph taken with the ZEISS TEM 9A – "flying carpet" preparation) Tissue sections obtained by ultramicrotomy are compressed by the cutting force of the knife. In addition, interference microscopy of the cut surface of the blocks reveals that the sections are often not flat. With Epon or Vestopal as embedding medium the ridges and valleys usually do not exceed 0.5 μm in height, i.e., 5–10 times the thickness of ordinary sections (1).
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