Transmission Electron Microscope

The basic definition of the Transmission Electron Microscope is used to view thin specimens (tissue sections, molecules, etc.) where electrons can pass through generating a projection image. In this way, the TEM is analogous to the conventional (compound) light microscope with the caveat of being more powerful. Credited with the invention of the electron microscope are German electrical engineer Max Knoll and German physicist Ernst Ruska. They overcame the barrier to higher resolution that had been imposed by the limitations of visible light in 1931 at the Berlin Technische Hochschule (Institute of Technology). Since the development of the first electron microscope, resolution has defined the progress of the instrument. The goal was to achieve atomic resolution – the ability to see atoms – over the course of decades of course.

Some of the earliest microscopes merely proved the concept that electron beams could, indeed, be ‘tamed’ to procure visible images of matter. Soon, the electron microscopes of the 1930s had theoretical resolutions of 10 nm, which were being designed and produced, and by 1944 this was reduced further to 2 nm. Increases in the acceleration of the electron beam voltage accounted for much of resolution improvement. New developments in the technology of the electron lens minimized abnormalities and provided a clearer picture, contributing to improved resolution, along with better vacuum systems and brighter electron guns. Throughout the development of this instrument, the main driving force was to increase the resolution of electron microscopes.

Like all technological advancements, when the electron microscope had reached the commercial level, economic factors set into its development path, as manufacturers set variations on the pricing. What occurred was usually the highest-resolution offering (with a high price tag) being offered next to a lower-resolution instrument for researchers. More advanced instruments requiring highly-trained technicians to operate them were offered next to simpler versions that could produce results after just a few hours of training. Thus, the second driving force of electron microscopy were the needs of the scientist and ‘microscopist’. While engineers might be driven to achieve the highest resolutions possible as a technological feat, they had to temper this drive in considering what the marketplace desired. Today, they can sell on the market approaching upwards of $1 million to the lowest price of around $120.