Ernst August Friedrich Ruska

The German engineer Ernst August Friedrich Ruska (1906-1988) designed and built the first electron microscope, for which he was awarded the Nobel Prize in Physics in 1986.

The electron microscope, like many other complex technological developments based upon current scientific research, cannot be associated exclusively with a single inventor. In the early 1930s several laboratories were at work on a super-microscope that would use electron waves, instead of light waves, to magnify a microscopic specimen. However, it is generally agreed that the German engineer Ernst Ruska designed and built the first working electron microscopes (1931-1933). Ruska's contribution to the science of physics, and to its applications in the fields of biology and medicine, was recognized in 1986 when he was awarded the Nobel Prize along with two other pioneers of modern microscopy, Gerd Binnig and Heinrich Rohrer.

Ernst August Friedrich Ruska was born in Heidelberg, Germany, on December 15, 1906. His immediate family and his closest relatives were all involved with the sciences in academic settings and it was assumed that Ernst would enroll at a German university in order to pursue a degree in science. But Ruska, who had long been fascinated by the technological progress of the early 20th century, had other plans. He entered technical colleges in Munich and Berlin to study first aeronautics and then electrical engineering. Ruska was awarded a Doctorate degree by the Berlin Institute of Technology in 1934. The topic of his doctoral dissertation was electron optics and the technology of electron microscopy.

For the next decade Ruska worked in engineering research for several German firms and in 1944 he received his Habilitation, the highest degree offered by the German university system. After World War II Ruska held a number of distinguished posts in German universities, including the directorship of the Institute of Electron Microscopy, Fritz Haber Institute, West Berlin (1957-1988).

Beginning in 1939 he had received numerous prizes and awards from German and foreign institutions, culminating in the 1986 Nobel Prize for Physics. He was honored for his contributions to physics, electronic technology, microscopy, and medicine. Ruska died in West Berlin on May 30, 1988.

The electron microscope is a technological device that draws upon the work of modern physicists, and Ruska possessed the ability to move easily between the worlds of physics and electrical engineering. As a student he was fortunate to have had professors who encouraged him in research projects that brought him close to the frontiers of modern physics. The invention of the electron microscope could only have been successfully completed by someone who had a deep understanding of the theoretical and practical aspects of electricity.

Quantum mechanics supplied the theoretical basis for electron microscopy. This theory was developed early in the 20th century to explain small-scale physical events such as the motion of electrons. In 1924 the French physicist Louis de Broglie claimed that electrons moving at very high speeds have a wave-like nature. De Broglie's wave particle hypothesis opened the way for the establishment of wave mechanics in physics and suggested that a microscope might be built using electron waves. Because the wavelength of an electron is about 12,500 times smaller than the wavelength of visible light, an electron microscope is much more powerful than a magnifying system using ordinary light. Specifically, a visible light microscope magnifies an object up to 2,000 times its original size; an electron microscope, 1,000,000 times its original size.

The first order of business for a designer of an electron microscope is the construction of a set of "lenses" to focus the beam of electrons. In 1928 Ruska's professor, Max Knoll, assigned him this task. Within three years Ruska constructed an electron microscope using two specially-designed magnetic coils to focus the electron beam for the purposes of magnification. Ruska's primitive model of 1931 was able to magnify a mere 17 times, but it yielded a sharp image and proved that an electron microscope could be built.

Within a few days after Ruska announced his new microscope one of his German competitors, Reinhold Rüdenberg, applied for several patents covering electromagnetic and electrostatic magnification of electron beams. Although Ruska was forestalled from obtaining the first patent for his invention this did not stop him from embarking upon plans to develop a commercial model of an electron microscope. By 1938 Ruska, working with a team at the Siemens electrical company, had constructed prototype electron microscopes capable of magnifying 30,000 times.

As the electron microscope moved towards commercialization and eventual mass-production, there were several problems that had to be overcome. First, there was the need to improve the magnification and resolution of the instrument in order to produce sharp images that revealed the fine details of the specimen under observation. Second, it was necessary to devise ways to expose biological specimens in the electron microscope without their being destroyed. The intense electron beam incinerated samples of living matter placed in its path.

Solutions to these and other problems were undertaken by Ruska, but groups of physicists, biologists, and engineers in Europe and America joined in the work of improving electron microscopes. These groups refined the electron microscope, making it a standard instrument in advanced laboratories of biology, medical science, metallurgy, and crystallography. Although the modern electron microscope has been put to many different uses, it has proved to be crucial in the investigation of the cellular structures of living material.

Further Reading

• Some information on Ernst Ruska can be found in Frank N. Magill, The Nobel Prize Winners: Physics, volume 3 (1989) and in Bertram Schwarzschild, "Physics Nobel Prize Awarded for Microscopes Old and New," Physics Today (January 1987). Dennis Gabor, The Electron Microscope (1944); L. Marton, Early History of the Electron Microscope (1968); and Peter W. Hawkes, editor, The Beginnings of Electron Microscopy (1985) cover the history of electron microscopy and Ruska's contributions to its development.