The standard light microscope is ubiquitous, from children’s science kits to industry labs. They are very useful instruments but that have their limitations. Standard light microscopes typically magnify by 5, 10 and 20 times. The use of a combination of these lenses gives a larger magnifying ability. The world’s most powerful light microscope can see objects down to 500 nm [1], but due to the wavelength of light this is the limit.
This is where electron microscopes come in, instead of using the light reflecting off the sample, electron microscopes fire a beam of electrons. The wavelength of the electrons are significantly smaller than the wavelengths of visible light, this allows gives the microscope a much higher resolving power. There are different types of electron microscopes, the ones I will be talking about are scanning electron microscopes (SEM) and transmission electron microscopes (TEM), these differ as the electrons reflect from the sample in the SEM and they transmit through the sample in the TEM. These are used in a number of different industries and can be used for both biological and non-biological.
The electron microscopes only provide visual information of the sample, although different components are being added for increased functionality. Electron energy loss spectroscopy (EELs) and energy dispersive x-ray spectroscopy are good examples of this as they both provide elemental analysis of the sample.
Electron microscopes are incredibly sensitive pieces of equipment and a number of different factors can warp and distort the results. Fluctuating magnetic fields and vibrations are the main issues. Since the objects they are viewing can be about a angstrom in length, the smallest fields and vibrations can be seen. Therefore, electron microscopes are typically surrounded by a Faraday cage, which acts similar as noise cancelling but for electromagnetic fields. Fluctuating electromagnetic fields (from overhead wires) can cause large disturbances and ruin the imaging. Similarly, any vibrations will distort the images. This means that it is the important the electron microscope is situated away from events such as heavy traffic.
It is a lot more simple to have the electron microscopes situated in quite areas rather than creating the the equipment to compensate, so smart planning is required. There are examples of the issues above seen within Trinity college; there are two areas with electron microscopes, the advanced microscopy lab (AML) and the CRANN research institute. The CRANN building is located in a busy area within Dublin, with the DART constantly crossing overhead, plenty of traffic and electrical wiring. This causes a lot of interference, to try reduce this, the microscopes were built on a separate foundation to rest of the building, which travelled all the way down to bedrock. This was an attempt to reduce the impact of the vibrations. There are also Faraday cages around them, but despite this there are still issues using the instruments as the DART passes over head. Compared to CRANN, there are a lot more electron microscopes situated at the AML. It is a quieter area, which is a lot better suited to housing the microscopes.
Electron microscopes are probably some of the most sensitive instruments there are, and as we look at smaller and smaller objects more and more things that were once negligible become significant issues. There will never be the perfect place to escape all the issues so all that can be done is to come up with new ideas to compensate and dampen these external influences.
References
[1] Lynn Charles Rathbun (2013); “World’s most powerful microscope” [online]
Accessed from: https://www.nanooze.org/worlds-most-powerful-microcope/#:~:text=The%20smallest%20thing%20that%20we,about%201000%20nanometers%20in%20size.
