Electron microscopes (EM’s) are very sophisticated and powerful pieces of equipment that have revolutionized the world of science and medicine. Thanks to the EM for the first time scientists have been able to observe and produce genuine images of viruses, bacteria and other cells in mind blowing detail.
Electron microscopes utilize a beam of electrons in order to create an image of much higher magnification and resolution when compared to standard light microscopes. There are two types of electron microscope: scanning electron microscope (SEM) and transmission electron microscopes (TEM) which both use electrons to produce an image but use them in different ways.
Scanning Electron Microscope
SEM’s uses a primary electron beam which scans across the surface of the specimen and interacts and excites secondary electrons on the surface of the sample. This emits a signal that allows the SEM to build an image.
Transmission Electron Microscope
TEM’s emit a high voltage electron beam through a thin slice of the specimen and the structure of the specimen is constructed and magnified by a photographic plate, fluorescent screen or a sensor which records the spatial variation and density of the resulting electron beam.
Disadvantages of Electron Microscopes
Electron microscopes are a fantastic way to study samples in high detail and are used to create images on a wide range of samples including; cells, molecules, microorganisms, metals, crystals and more. However electron microscopes do have a few disadvantages which would prevent them from being used outside of the clinical or research lab environment.
Cost – The first of these disadvantages is the expense. Not only are the cheapest of SEM’s still quite an expensive piece of equipment (lowest price: $2,500) but replacement parts for them can set you back too. For a laboratory grade professional SEM you are looking at a price around the $10,000 mark whereas TEM’s require a quote request form the manufacturers.
Training – Another disadvantage is the amount of training and knowledge required to operate an electron microscope. For instance, samples must be prepared and observed in such a way to minimize artifacts and when the resulting image is analyzed one must be able to recognize these artefacts to obtain proper results. This requires a good amount of professional training and experience.
Space – The electron microscopes are large and are usually kept in a designated room which is fitted appropriately for the microscope itself. A room designated for the microscope would ensure there is no interference with the electrons that the machine utilizes and produce much better images.
Living cells – In comparison to the light microscope, the electron microscope can only observe an image of a fixated sample, unlike the light microscope which can view specimens when they are alive and motile. Therefore it is not as useful as the light microscope for studying the behaviors, motility or moving structures of cells and microorganisms.This is perhaps the biggest disadvantage, as medical research often requires living cells in order to track various biomolecules and monitor important changes.