Electronic microscope

November 1, 2021

An electron microscope is an image width instrument . In 1590 the first optical microscope was invented by Zacharias Janssen which worked by the principle of refraction. From there, the design became more and more sophisticated to reach higher levels of magnification and allowed the advancement of sciences such as biology and the beginning of others such as bacteriology.

However, by the 19th century, microscopes had reached their theoretical limit of magnification. But this did not stop their advances but motivated the creation of a microscope that would work on another principle. Thus in 1931 Max Knoll and Ernst Ruska created the first electron microscope, which does not operate by refraction but by electrons.

The difference in magnification between optical and electric microscopes is really significant, being the limit of the optical ones around 1500 X maximum and any increase higher than this would represent an empty magnification, that is, it does not have good resolution and therefore does not provide more. information. While the electronics reach even 100,000 X.

What is an Electron Microscope?

The electron microscope is a magnifying instrument that uses electrons for magnification resolution. But how does this work? It is thanks to the wavelength; the visible spectrum of light is made up of electromagnetic waves, in which the distance is measured between two maxima of the field, between two wave cycles.

Electron microscopes do not use visible light but electrons that interact with the sample; the wavelength of the electrons are inversely proportional to the speed at which they move and when they are accelerated they achieve extremely short wavelengths.

These short lengths provide a sample width with excellent resolution. Acting the electrons on the sample as light they recreate the enlarged image of it. There are different types of electron microscopes and they have been modified and refined since the first prototype in 1931.

The electron microscope is composed of various parts such as electromagnetic lenses, electron source, vacuum chamber and others; requiring a computer to process the images obtained by the electrons and make them definable to the human eye. Going even to produce three-dimensional images.

What is the Electron Microscope for?

The electron microscope by providing so much breadth has served the development of many sciences. This is used to view and analyze structures of cells , microorganisms, viruses and other samples with microscopic structures that are not visible through optical microscopes.

If both optical and electronic microscopes fulfill the same function, the difference is the scope of the electronic with respect to the optical. By giving amplitude with good resolution , details of the structures can be appreciated , which provides additional information on the samples to be studied, allowing a broader knowledge of it.

Uses of the Electron Microscope

One of the branches that has benefited the most from the use of the electron microscope is biomedical research . Since they are ideal for the analysis of the functioning and molecular structures of microorganisms. But its use is not limited to the research field. The industrial sector also benefits greatly from its functions.

It is used for quality control analysis and for the development of new products ; as it is used to monitor the morphological procedure of the products. An example is the construction of semiconductors, in which the electron microscope is used for the production of chips and microchips.

In paleontology, geology, archeology and geomining, the electron microscope is also useful; Reduces the risk of mineral exploration by evaluating land, as well as oil and gas fields. In many disciplines it was used to know and inspect the morphological structures of the object of study.

Types of Electron Microscopes

There are two basic types of electron microscopes ; the first to be created was the transmission electron microscope (MET) in 1931 and later the scanning electron microscope (SEM) was designed in 1942. The main difference between these types of microscopes is the state of the sample, which in the MET it must be cut and intact in the SEM.

  • Transmission Electron Microscope

In this type of microscope electrons are directed to the sample, which must have slight cuts, the length of these must not exceed a few thousand angstroms, remembering that an angstrom corresponds to 0.1 nanometer. The electrons bounce off or pass through the sample and impregnate the magnified image on a fluorescent screen or photographic plate placed under the sample.

  • Scanning Electron Microscope

To use the SEM, it is not necessary to alter the sample; This directs a concentrated beam of electrons to the sample, which performs a punctuated scan across its surface , without going through the sample. These are dispersed and automatically counted. Each point builds the amplified image of the sample and the greater the quantity counted, the sharper the image has.

The SEM shows a sharper image, reaching even 3D recreations of the sample surface, it can even enlarge the sample 200,000 times; making it more powerful than the MET. There is also STEM, an electron microscope that combines the capabilities of both, or that of an electron probe, with the ability to analyze X-rays.

Features of the Electron Microscope

Electron microscopes are instruments that, although they fulfill the function of a microscope to enlarge the image of a sample, their way of doing it is somewhat different, enough to require a totally different structure. So to familiarize you with this type of instrument, I will proceed to describe its characteristics:

  • Electron gun

It is responsible for expelling the electrons that impact the sample to enlarge its image. Electrons can be generated by thermionic emission or by field emission.

  • Condenser

Made up of electromagnetic lenses to guarantee the focus of the sample. Many times a double condenser is used to ensure that the sample is kept intact; especially in the MET type.

  • Electromagnetic lenses

These lenses are electromagnetic fields that are used to direct electrons to the sample. This is due to the fact that they are positive and attract electrons to be negative, causing their deflection to the sample.

  • Vacuum system

The electrons must be in vacuum conditions to avoid their dispersion through the air molecules; otherwise sharp images may not be obtained. The high vacuum of the microscope is produced by mechanical pumps that extract air.

  • Registration system

This is the screen where the image is projected, through fluorescence that transforms the kinetic energy of electrons into light. They can also be recorded on photographic film.

The composition of electron microscopes is quite similar, with the difference that the scanning one has a scanning generator to scan by default and a secondary electron detector. The rest of its composition being identical to that of transmission. In the same way, it is always recommended to read the specifications of the model to be purchased.

Importance of the Electron Microscope

The electron microscope is an instrument of indisputable utility, if in itself the optical microscope generated great advances in the biological, chemical and medical sciences; Thanks to the magnification by the electron microscope, development has been able to take place on an even larger scale. Allowing to know the operation of microscopic structures.

Although it is used in a large number of areas, the ones that most benefit from it is medicine and biology; since his objects of study are made up of these organisms imperceptible to the human eye.

Both the transmission and scanning microscopes are widely used today and progress continues to improve their performance, reaching greater ranges of amplitude and resolution. These are part of a series of laboratory instruments that enable investigative work in various areas.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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