This article discusses the electron microscope's advantages, potential applications, and future outlooks.
An electron microscope emits a beam of high-energy electrons for illumination. It offers a better resolving power than light microscopes and may expose the structure of miniature objects since an electron’s wavelengths are up to 100,000 times shorter than visible light photons.
While conventional light microscopes are constrained by diffraction to approximately 200 nm resolution and usable magnifications below 2000, a scanning transmission electron microscope has achieved more than 50 pm resolutions in an annular dark-field imaging model and magnifications of up to roughly 10,000,000.
Development of the Electron Microscopes
Although Hans Busch purportedly applied for a patent for an electron microscope in 1928, he did not build the microscope. Instead, he created the first electromagnetic lens in 1926.
The first electron microscope was developed in 1931 by Ernst Ruska and Max Knoll, two physicists and electrical engineers from the University of Berlin. This prototype, which had a four-hundred-power magnification capability, was the first to demonstrate the capabilities of electron microscopy. The patent on the electron microscope was obtained in the same year by Reinhold Rutenberg, the scientific director of Siemens-Schuckertwerke.
In 1933, Ernst Ruska improved the initial design to create an electron microscope that could produce images with a better resolution than optical microscopy. He teamed with Bodo von Borries and Helmut Ruska in 1937 to develop methods for putting the theories into practice, such as looking at biological samples.
Manfred von Ardenne created the first scanning electron microscope in the same year. In 1938, Siemens-Schuckertwerke offered the public the first commercial electron microscope.
Transmission electron microscopes started to become more widely accessible after this in other parts of the world, including North America.
In addition to Heinrich Rohrer and Gerd Binnig for creating the scanning tunneling microscope, Ernst Ruska received the Nobel Prize in Physics in 1986 for the invention of the electron microscope (STM).
Key Advantages of Electron Microscopes
The naked eye can distinguish two spots 0.2 mm apart with appropriate light. This spectrum is known as the eye's resolution capabilities. A lens or lens combination (microscope) may expand this range and enable the eye to view things substantially closer than 0.2 mm apart. A modern optical microscope has a 1000x magnification resolution.
Resolution is limited by lens amount and diversity, as well as the wavelength of the incident light. The average wavelength of white light is 550 nanometres (nm), with a range of 400-700 nm. This offers an optical microscope's potential resolution threshold of 200-250 nm. The electron microscope was developed when wavelength became the major limitation in optical microscopy. The much shorter wavelength of electrons permits increased resolution.
Electron microscopes employ electron beams focusing on electromagnets to enlarge and resolve small specimens.
Electron microscopes exhibit improved depth to map the surface of objects in three dimensions. When contrasted to light microscopes, electron microscopes offer two major advantages:
- They have a significantly wider magnification range (can detect smaller structures)
- They are considerably sharper and more detailed (can provide clearer and more detailed images)
Perhaps no instrument can rival electron microscopes in terms of their versatility for investigating bulk materials.
The electron microscope is vital in any discipline requiring the morphological characterization of materials.
Numerous applications need just minimal specimen amount and preparation. Many applications offer rapid data acquisition. The electron microscope offers intuitive, user-friendly designs. Modern technology produces information in readily transferrable digital forms.
The potential to observe the three-dimensional structures of materials is another benefit of the electron microscope over the optical microscope. High-resolution cross-sections of objects are produced using electron microscopes. Electron microscopes may also reveal the sample's chemical makeup.
Potential Applications of Electron Microscopes
Product development and manufacturing
In the production process and product development, industrial usage of electron microscopy is common. For example, semiconductors and other electronic components are created and produced using electron microscopes for high-resolution imaging. Automobile, clothing, pharmaceutical, and aerospace sectors frequently employ electron microscopes in their manufacturing processes. Various industries can use electron microscopy for process control and industrial failure analysis.
Organic material analysis and mining
Characterizing and analyzing organic materials using electron microscopy is possible, which is important for mining businesses.
The microscopes can swiftly and automatically produce quantitative, unbiased information about the surroundings.
Oil and gas industries
Oil and gas corporations may also use the technology to scan a region and gather data about it. This can aid in lowering the risk involved in oil and gas exploration and extraction. For instance, the reservoir, seal, and source rocks' quantitative lithotype and porosity properties can be discovered. It may also improve and confirm data included in geological models created from seismic, wireline, and mud logs.
Forensic science uses electron microscopy to provide data that may be used as evidence.
A relevant material, such as gunshot residue, a sample of garment fibers, blood, or another biological substance, may be examined in-depth using an electron microscope.
Compared with other techniques, electron microscopy provides more information for forensic experts.
Similarly, microorganisms, cells, big molecules, biopsy samples, metals, and crystals are just a few of the biological and inorganic objects that may be examined under an electron microscope to determine their ultra-structure. Electron microscopes are often used in industry for failure analysis and quality control.
Recent Research and Developments of Electron Microscopy
The on-axis aberrations of the objective lens have generally been decreased by over one order of magnitude, and the resolution has increased by more than a factor of three, by appropriately rebuilding an EM’s electron lenses.
Significant advancements have been accomplished in low-voltage scanning electron microscopy.
The scanning electron microscope's shrinking is another area of progress. For low-voltage applications, tiny high-resolution electrostatic columns that are only a few millimeters high have been proposed, and tiny permanent magnet columns with heights under 100 mm have also been constructed.
The fascinating idea of making the column or perhaps the entire EM portable is made possible by these kinds of improvements. Small-scale permanent magnet EM columns provide new mobility options.
Recent developments in electron microscopy methods and functionality include sequential block-face SEM (SBEM), which helps examine ultrathin tissue slabs removed using an ultramicrotome and subsequently placed into the electron microscope.
In the biological sciences, the development of Focused Ion Beam Electron Microscopes (FIB) represents a significant step forward in electron microscope technology.
Several general advancements in electron microscope equipment have been made in recent years. For instance, upgraded lenses and sensors boost the EM's resolution capability. These include small versions of scanning sections for particle spectrophotometers, analyzer and etchings, and lithographs for computer chips.
The Future of Electron Microscopes
It is clear that compared to earlier versions, contemporary electron microscopes can now produce pictures with a far better magnification and resolution. However, Ernst Ruska's initial prototype continues to serve as the foundation for the concepts of the electron microscope.
With enhanced resolution that enables the viewing of minuscule objects such as atoms, electron microscopes have exceeded many of the limits of optical microscopes.
Improvements to the electron microscope are still being developed today. For instance, a scanning electron environmental microscope that can observe specimens with moisture is currently being developed. It maintains a low vacuum in the sample chamber.
Recent advances in ultrafast imaging and diffraction have created a new field for studying nanoscale structure dynamics. It has become one of the most important future objectives for electron microscopy.
Ultrafast electron microscopy integrates the higher spatial resolution of traditional electron microscopy with ultrafast short electron impulses to detect electronic and subatomic motion on their native time and length scales.
References and Further Reading
Inkson, B. J. (2016). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for materials characterization. Materials Characterization Using Nondestructive Evaluation (NDE) Methods (pp. 17–43). Woodhead Publishing. https://doi.org/10.1016/B978-0-08-100040-3.00002-X
Muscariello, L., Rosso, F., Marino, G., Giordano, A., Barbarisi, M., Cafiero, G., & Barbarisi, A. (2005). A critical overview of ESEM applications in the biological field. Journal of Cellular Physiology, 205(3), 328–334. https://doi.org/10.1002/jcp.20444
Spence, J. C. H. (1999). The future of atomic resolution electron microscopy for materials science. Materials Science and Engineering: R: Reports, 26(1), 1–49. https://doi.org/10.1016/S0927-796X(99)00005-4