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Retrospect

A very small universe

70 years ago, Ernst Ruska created the electron microscope in Germany

The advances of medicine and the creation of new areas for scientific research, like nanotechnology, are directly related to the advances in the techniques for using the electron microscope. “Today, one of the great issues of science is getting to know the exact structure of a few molecules and finding out how they modify themselves,” explains Edna Freymuller Haapalainen, the director of the Electron Microscopy Center of the Federal University of São Paulo (Ceme/Unifesp). “This kind of research is fundamental for establishing the relationships between the biochemical and morphological data, so as to understand the intricate and dynamic organization of a cell.”

One of the principal tools for understanding these processes is the electron microscope. In its essence, it is a variation of the old light microscope invented in 1590, when the Dutchmen Hans and Zacharias Janssen, who were working with glass, adjusted two lenses inside a tube for the first time. The great leap forward in microscopy took place in the 30’s. Ernst Ruska (1906-1988), a German, was working at the High Voltage Institute, in Berlin, with Max Knoll, and in 1928 was already interested in magnetic fields and “electron lenses.” In 1931, Ruska and Knoll built the first prototype of an electron microscope. “With this instrument, two of the most important processes for reproducing images were introduced: the principles of emission and radiation,” according to Ruska’s words in a text for the Nobel Foundation.

“In 1933, I was able to put into use an electron microscope made by me, which for the first time brought a better definition than the light microscope.” The advantage lies in the increased resolution of the samples observed. The light microscope makes it possible to see a sample between 1,000 and 1,500 times larger than its real size – cells and microorganisms, for example. The electron microscope magnifies up to 200,000 times, for biological material and up to 1 million times for other kinds of materials, making it possible to observe organelles, DNA, proteins, etc. But it is not enough to get a larger image: it has to have good resolution.

To achieve the two things, some technological advances were necessary. The sample needs to be as thin as possible and put into the vacuum where the electron beam works to form the image. Furthermore, to be able to pass through the object and register the image on a film (or on a computer screen), the electrons need to be accelerated (with more energy). These characteristics make it possible to achieve a magnified image and with resolution, but prevent the observation of living beings – the electrons “kill” the sample when they pass through it in the vacuum.

The electron microscope is equally useful for analyzing inorganic samples and, for example, for checking for faults in metal alloys, amongst numerous other uses. Ruska won the Nobel Prize for Physics in 1986. Also sharing the prize with him were Gerd Binnig, a German, and Heinrich Rohrer a Swiss, who in 1981 created another kind of microscope, the scanning tunneling electron microscope, which is neither optical nor does it use lenses, but provides images of molecules and atoms with an excellent definition.

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