There is a Total of 4 Types of Electron Microscopes available, which include Scanning Electron Microscope, the Cyro-Scanning Electron Microscope, Transmission Electron Microscope, and Electron Backscatter Diffraction Microscope, Let’s see what are they, how they work step-by-step.
What is Electron Microscope
For many years we have been using compound microscopes and light microscopes for our daily scientific researches, but the need for a better and advanced microscope has been there, always a need, with the discovery of electron microscopes everything changed.
The invention of microscopes had been available since the beginning of the 17th century but a lot of improvements were made in the quality of glass lenses in the early 19th century.
The branch of biology dealing with microscope design slide preparation and examination is called cytology.
The light microscope uses light as a source of radiation and has shown us inside cells it shows us simple structures like the nucleus the cell wall and the cell membrane.
A light microscope is still used in basic studies in schools today electron microscopy then came to the electron microscopes which made our microscopic world more detailed than the electron microscopes.
With the help of the Electron Microscope, we not only saw the cell wall the nucleus, and the cytoplasm but we also saw the more minute organelles like the mitochondria, endoplasmic reticulum, and the Golgi apparatus as well.
How Electron Microscope works
The light microscopes were doing great but no matter how much their designs improved there was an extent to which the light microscopes could not show anything smaller than 200 nm.
As the problem with the light microscope that could not be seen electrons are subatomic particles that have a negative electric charge and are found surrounding the nucleus of an atom called the neutron.
When metal becomes very hot some of its electrons gain so much energy that they escape from their orbits like shooting stars the energy in free electrons is associated with the proportion of waves in the form of light.
The higher the energy the shorter the wavelength electrons are a very suitable form of radiation for a microscope.
For two major reasons firstly the wavelength is extremely short and secondly, because they are negatively charged they can be focused easily using electromagnets of the electron microscope.
The magnet can be made to alter the path of a beam similar to how a glass lens is made to bends the light.
There are two types of electron microscopes in use today the transmission electron microscope TEM and the scanning electron microscope what we also call SEM Electron Microscope.
In the transmission electron microscope, the beam of electrons is passed through the specimen before being viewed only those electrons that are transmitted are seen this enables us to see different components inside the cells.
Types of Electron Microscope
Scanning Electron Microscope (SEM)
Let’s talk about scanning electron microscopy in a little bit of detail in like all the other types of electron microscopy it depends on the release of electrons to illuminate the targeted object.
We are going to see about working of scanning electron microscope internal parts of scanning microscope electron gun anode, condenser lens objective lens x-ray detector secondary detector a high-energy electron beam is produced by an electron gun the beam is focused to a spot off about handling strong diameter and made to scan the surface of the specimen.
The scintillator collects the secondary or scattered electrons and converts them into light signal backscatter electrons reflect the surface and deeper from the specimen is also known as reflected electrons
For example, whatever object we want to study in light microscopy we use light right in frozen microscopy also is a part of light microscopy.
we use photons to excite the particle or also we use simple plain white light to illuminate the object so that we can see it by the zooming feature of the microscope with a better resolution.
Now the idea with electron microscopy is to use electrons instead of photons instead of light particles simply use electrons.
In the case of SEM, the electron beams can be over the surface of the sample, and based on scattered electrons sample can be any thickness and mounted on an aluminum stub.
Cyro Scanning Electron Microscope (CSEM)
Proteins are the building blocks of ourselves understanding their shape and how they fit together could help us treat pain and even cure diseases scientists have been trying to get a better protein.
But for many years we are unable to see the exact structure of a protein molecule, which is 1000 times smaller than a protein molecule.
Traditionally scientists use a technique called x-ray crystallography to take pictures of the tiny proteins for x-ray imaging to work requires proteins are packed together into stable organized crystal x-rays which pass through the sample to create an image, but some of the body’s most important proteins are too, small, uneven, floppy or Wiggly to line up into a crystal-like form for better imaging.
Scientists at UCSF have developed a better way to view these elusive proteins if you have a floppy molecule at all they just become more and more challenging to crystallize really.
The problem was that these are big complicated systems and coming up with new ways of studying them required thinking about electron microscopy.
The reason it worked is that we keep the approaching in a very seen layer of liquid and we’ll freeze them this technique is called cryo-electron microscopy.
In this an electron gun shoots electrons at the speed of light passing through the sample then an especially designed high-tech camera captures the electrons to form an image.
The camera not only improved imaging condition we’ll give you much better sharp image it can record a movie instead of a steady picture.
if you had a still picture and I was doing this with my hand during the picture out of a blurry hand picture but with a movie, you could actually see the different steps
A computer algorithm sorts the images and finds pictures of the protein in the same orientation then software builds a composite an accurate high-resolution three-dimensional image of the protein and we use in the computation method to average many hundreds of thousands of molecules or tens of thousands and together to generate a three-dimensional structure a structure like this one
Transmission Electron Microscope (TEM)
Ernst Ruska is considered as the Father of Transmission Microscopy, he was the inventor in the years 1932 to 1933 he came up with the concept and developed a prototype of the TEM, and then he received his Ph.D. for this work.
After his invention, he worked in the field of electron optics helped develop commercial terms in the first commercial TEM went on the market in 1939, and here he is with a later model he shared his Nobel Prize with Bennigan’s rower who developed the scanning tunneling microscope or STM in 1986.
so this is similar to electron microscopes you have an electron gun here at the top the simplest form of the electron gun would be a tungsten filament where you have a wire basically a tungsten wire that’s bent into a sharp tip and then you pass a current through that wire.
And then the wire heats up and then the electrons are kicked off due to their thermal energy this is called thermionic emission.
A thermionic ignition of the tungsten filament TEM they’re accelerated from the cathode to the anode by a high voltage now in a standing electron microscope.
This voltage is on the order of saying up to thirty thousand volts and a typical SEM in a typical TEM the voltage is a factor of 10 higher.
So typical TEM’s have voltage ranges that go from say a hundred thousand volts to three hundred thousand volts right now the reason that the accelerating voltage and the TEM have to be higher is that you have to accelerate those electrons through the sample.
So the electrons have to penetrate through the sample and come out the other side in order to form a bright-field image, which is our final product.
so the electrons are accelerated away and then they move down the column the first thing they encounter is the condenser lens.
Now the lenses of SEMS and TMS are basically the same ideas okay their electromagnetic lenses you pass current through the lens and then that generates a magnetic field and through the Lorentz force law as is equal to QV cross B that steers the electrons and forces them to condense to form a probe.
In the case of TEM, the electron beam passes through a thin sample based on transmitted electrons especially prepared thin samples are supported on stem greeds specimen and same stage in the chamber at the bottom of the column.
And then the specimens in thin stage halfway down the column and the imaging same shown on tv monitor while the team image is shown on fluorescent screen the image
Electron Backscatter Diffraction Microscope (EBSDM)
Electron Backscatter Diffraction or EBSD for short is an analysis technique based on a scanning electron microscope SEM.
It measures the local crystal orientation with sub-micron spatial resolution and can also be used for phase distribution analysis the following illustrates.
EBSD on the analysis of a duplex stainless steel sample failure susceptibility of an industrial pipe fitting is being examined by checking the presence of deleterious phases like sigma and kai brokers.
A high-performance quad tax EBSD system reveals this information fast and with great accuracy when the electron beam hits the steel sample a cloud of backscattered electrons is generated.
A phosphor screen placed within this cloud will transform each arriving electron into a photon thus transforming the backscattered signal into a visible light signal.
Then the diffracted part of the backscattered electrons is highly anisotropic and when interacting with the phosphor it will create a pattern, for instance, a Kikuchi pattern.
The Kikuchi pattern is captured by a high speed and high sensitivity CCD camera placed behind the phosphor screen and transferred to a computer where it is being analyzed.
Hundreds of patterns can be acquired and analyzed per second due to state-of-the-art hardware and software technology high-speed measurements allow the acquisition of large EBSD maps in very short times.
Electron Microscope Price in India
In India, the Price of Electron Microscope Ranges Between 1.03 Crores to 2.36 Crores, which is approximately 1,34,446.00 $ – 2,68,892.00 $ US dollars.