The electron microscope is an essential tool in many scientific fields, including biology, physics, and materials science.

Unlike the optical microscope , it uses electrons instead of visible light to observe extremely fine details. Thanks to its ability to achieve nanometric resolutions, the electron microscope allows the study of structures invisible with a conventional microscope.

This article explains why you should choose an electron microscope over a light microscope.

What is an electron microscope and how does it work?

Basic principle of electron microscope

An electron microscope uses a beam of electrons to illuminate the sample, unlike optical microscopes, which use visible light. Electrons have a much shorter wavelength than light, allowing for much higher resolution. There are two main types: the scanning electron microscope (SEM) and the transmission electron microscope (TEM).

The key components

The electron microscope consists of an electron source, electromagnetic lenses, and a detector. The source generates the electron beam, the lenses focus the beam on the sample, and the detector captures the signals produced by the interaction between the electrons and the sample. These elements work together to produce highly detailed images.

Why is the resolution of the electron microscope superior?

Limitations of the optical microscope

The resolving power of a light microscope is limited by the wavelength of visible light, approximately 400 to 700 nm. This means that it cannot distinguish details smaller than approximately 200 nm. This limitation prevents the observation of structures such as viruses or individual molecules.

Advantages of the electron microscope

Electrons have a wavelength much smaller than visible light, often less than 0.1 nm. This allows the electron microscope to achieve a resolution of up to a few nanometers. This makes it possible to observe internal cellular structures, nanostructures, or even individual atoms.

Practical applications of the electron microscope

In the life sciences

In biology, the electron microscope is used to study the structure of cells, viruses, and cell organelles. For example, it helped visualize the structure of SARS-CoV-2 during the 2020 pandemic. SEM shows the surface of cells, while TEM reveals their interior.

In materials science

In materials engineering, electron microscopy analyzes the chemical composition and structure of surfaces. Techniques such as electron diffraction or spectroscopy can identify the elements present in a material. This helps improve the properties of semiconductors, metal alloys, or nanomaterials.

Limitations and challenges of using the electron microscope

Strict terms of use

Unlike optical microscopes, electron microscopes require a vacuum in the viewing chamber to prevent collisions between electrons and air molecules. This complicates the handling of living biological samples, which must be prepared and fixed before observation.

Cost and complexity

Electron microscopes are expensive to purchase and maintain. They also require specialized training to use. In contrast, optical microscopes are affordable, easy to use, and suitable for many common observations.

Conclusion: Choosing the right microscope for your needs

The choice between a light microscope and an electron microscope depends on the observation objective. If you need to see nanoscale details, the electron microscope is essential. But if your work remains at the classical microscopic level, the light microscope is sufficient. Moreover, combined techniques such as correlative microscopy allow you to use both methods to obtain both a global view and precise details.

FAQ: Frequently Asked Questions About Electron Microscopes

What is the difference between an SEM and a TEM?

The scanning electron microscope (SEM) observes the surface of the sample by sending an electron beam that scans line by line. The transmission electron microscope (TEM), on the other hand, passes the beam through a very thin sample to observe its internal structure.

Is it possible to observe living samples with an electron microscope?

No, because the necessary vacuum damages living cells. Biological samples must be fixed, dried, and usually covered with a thin layer of metal before observation.

What are the costs associated with an electron microscope?

• An MEB can cost between €200,000 and over a million euros.
• Maintenance costs include consumables, electricity and staff training.
• Solutions such as shared services or technology platforms can help reduce these costs.