Electron microscopes

When looking at the fine structure of a cell, even a good light microscope is no longer capable of producing an image that is accurate enough. In this kind of a situation, an electron microscope is required. Electron microscopes provide higher magnifications and higher resolution images but cannot be used to view living cells.

The two most important applications of electron microscopy are the Transmission Electron Microscope (TEM) and the Scanning Electron Microscope (SEM). There is a big difference in their use. The TEM gives a cross-sectional view of the sample, whereas the SEM reveals the shape of the object's surface. Thus, TEM is closer to the principle of light microscopy. As the name implies, the light source of an electron microscopes are electrons, which are used to bombard the sample. The electron microscope has a much better resolution and depth of field than the light microscope. Electron microscopes, like light microscopes, have a light source and a lens system. The electron beam does not even penetrate the air, let alone the glass lens. Thus, the interior of the electron microscope is vacuum and the lenses are made of magnets instead of glass.

TEM tomography

Electron tomography is a technique used to observe relatively large structures from cellular organs to tissue samples. TEM is also used to scan sports injuries, such as tendon and muscle injuries. The structures to be scanned are 100 to 500 nm (nanometers) in size, and the resolution of the resulting image can display details as small as 4 nm. Although tomography is a great way to create three-dimensional images, it is also a very difficult method. Nowadays, about 100 images are taken during a time of two to four hours, with a full day of image processing. Transmission electron microscopy images are mainly used to determine the cross-sectional structures of cells.

SEM imaging

The scanning electron microscope, or SEM, produces images that display the surface shape of the sample with a resolution of ten nanometers (10 nm = 10-8m). SEM images are accurate over the entire shooting range. For those who are used to viewing 3D images, SEM images are easy to understand. However, complete three-dimensional images cannot be obtained with SEM. This would require combining images from different angles.

Because SEM focuses on the sample’s surface and its composition, the device is used to view the cause of sample-specific surface reactions. Thus, typical applications of SEM include coating inspections, examining the causes of fractures and examining surfaces for microbial contamination or rust damage.

AFM (Atom Force Microscope)

In addition to electron microscopes, the atom force microscope or AFM was developed in the 1980s. It is no longer based on visual observation but on "feeling" or "touching" the surface of the sample with a mechanical probe. AFM is a very versatile microscope used in electronics and chemistry research. It also has a number of biological uses.