Ruska, Ernst (1906-1988)

German physicist

The inventor of the electron microscope , Ernst Ruska, combined an academic career in physics and electrical engineering with work in private industry at several of Germany's top electrical corporations. He was associated with the Siemens Company from 1937 to 1955, where he helped mass produce the electron microscope , the invention for which he was awarded the 1986 Nobel Prize in physics. The Nobel Prize Committee called Ruska's electron microscope one of the most important inventions of the twentieth century. The benefits of electron microscopy to the field of microbiology and medicine allow scientists to study such structures as viruses and protein molecules. Technical fields such as electronics have also found new uses for Ruska's invention: improved versions of the electron microscope became instrumental in the fabrication of computer chips.

Ruska was born in Heidelberg, Germany, on December 25, 1906. He was the fifth child of Julius Ferdinand Ruska, an Asian studies professor, and Elisabeth (Merx) Ruska. After receiving his undergraduate education in the physical sciences from the Technical University of Munich and the Technical University of Berlin, he was certified as an electrical engineer in 1931. He then went on to study under Max Knoll at Berlin, and received his doctorate in electrical engineering in 1933. During this period, Ruska and Knoll created an early version of the electron microscope, and Ruska concurrently was employed by the Fernseh Corporation in Berlin, where he worked to develop television tube technology. He left Fernseh to join Siemens as an electrical engineer, and at the same time accepted a position as a lecturer at the Technical University of Berlin. His ability to work in both academic and corporate milieus continued through his time at Siemens, and expanded when in 1954, he became a member of the Max Planck Society. In 1957, he was appointed director of the Society's Institute of Electron Microscopy, and in 1959, he accepted the Technical University of Berlin's invitation to become professor of electron optics and electron microscopy. Ruska remained an active contributor to his field until his retirement in 1972.

Prior to Ruska's invention of the electron microscope in 1931, the field of microscopy was limited by the inability of existing microscopes to see features smaller than the wavelength of visible light. Because the wavelength of light is about two thousand times larger than an atom, the mysteries of the atomic world were virtually closed to scientists until Ruska's breakthrough using electron wavelengths as the resolution medium. When the electron microscope was perfected, microscope magnification increased from approximately two thousand to one million times.

The French physicist, Louis Victor de Broglie , was the first to propose that subatomic particles, such as electrons, had wavelike characteristics, and that the greater the energy exhibited by the particle, the shorter its wavelength would be. De Broglie's theory was confirmed in 1927 by Bell Laboratory researchers. The conception that it was possible to construct a microscope that used electrons instead of light was realized in the late 1920s when Ruska was able to build a short-focus magnetic lens using a magnetic coil. A prototype of the electron microscope was then developed in 1931 by Ruska and Max Knoll at the Technical University in Berlin. Although it was less powerful than contemporary optical microscopes, the prototype laid the groundwork for a more powerful version, which Ruska developed in 1933. That version was ten times stronger than existing light microscopes. Ruska subsequently worked with the Siemens Company to produce for the commercial market an electron microscope with a resolution to one hundred angstroms (by contrast, modern electron microscopes have a resolution to one angstrom, or one ten-billionth of a meter).

Ruska's microscope—called a transmission microscope—captures on a fluorescent screen an image made by a focused beam of electrons passing through a thin slice of metalized material. The image can be photographed. In 1981,Gerd Binnig and Heinrich Rohrer took Ruska's concept further by using a beam of electrons to scan the surface of a specimen (rather than to penetrate it). A recording of the current generated by the intermingling of electrons emitted from both the beam and specimen is used to build a contour map of the surface. The function of this scanning electron microscope complements, rather than competes against, the transmission microscope, and its inventors shared the 1986 Nobel Prize in physics with Ruska.

In 1937, Ruska married Irmela Ruth Geigis, and the couple had two sons and a daughter. In addition to the Nobel Prize, Ruska's work was honored with the Senckenberg Prize of the University of Frankfurt am Main in 1939, the Lasker Award in 1960, and the Duddell Medal and Prize of the Institute of Physics in London in 1975, among other awards. He also held honorary doctorates from the University of Kiev, the University of Modena, the Free University of Berlin, and the University of Toronto. Ruska died in West Berlin on May 30, 1988.

See also Microscope and microscopy