When Ernst Leitz took over Carl Kellner’s Optical Institute in Wetzlar in 1869, it never occurred to anybody to use optical microscopes to look at small structures measuring a few nanometres. After physicist Ernst Abbe had developed the fundamentals and the theory of modern optics in 1873 that the maximum microscopic resolution was limited to about half the length of light waves, or 200 to 350 nanometres, this limit was considered to be permanent – up to a few years ago.
Thinking out of the box. Physics professor Stefan Hell achieved the crucial breakthrough in the early 1990s. Hell, today professor of physics at the Max Planck Institute in Göttingen and head of the Department of Nano-Bio-Photonics, discovered fluorescent microscopes, which completely turned conventional doctrine on its head by achieving optical resolution far below 100 nanometres.
STED technology, invented by Hell, makes it possible to look deep into the nano-cosmos. The STED microscope makes it possible to distinguish smaller details of up to 50 nanometres.
The physical approach of this new kind of fluorescence process is called “STimulated Emission Depletion”, for which Hell was awarded the German Future Award in November 2006. Additional, ring-shaped points of light prevent individual fluorescent dots from fluorescing at the edges. The remaining points of light can be reduced in size to the point where remote structures can be shown a few nanometres apart. Today, STED microscopes manufactured and sold by Leica Microsystems on an exclusive licence basis are used in top research centres for purposes such as investigating molecular structures within cells or signal transmission processes between nerve cells. Being able to observe how proteins and molecular complexes move, function and interact within cells helps science to understand how diseases develop and can be treated.
Combined precision. In the field of nanotechnology, confocal microscopy and interferometry have since been combined in a single sensor head for industrial uses. The dual-core Leica DCM 3D measuring microscope is based on a fast-reaction micro-display positioned in the luminous-field diaphragm. Luminous-field, interferometry and confocal images can be generated via the micro-display. The combination of the confocal micro-display, two light sources and two cameras generates high-resolution 3D measurements and unlimited depth of focus. Both rough and smooth surfaces and edges of up to 70 degrees can be recorded within seconds. At the same time, differences in height of a few nanometres up to several millimetres can also be measured. The 3D microscope is used for a wide range of measuring tasks in research and development, in quality assurance laboratories and automated online process controls requiring high speeds and resolutions of up to 0.1 nanometres.
The author is a graduate in ecotrophology and a state certified communications specialist. She specializes in medicine, business, services and technology. Anja Schué has been technology and applications editor at Leica Microsystems with responsibility for production of the reSOLUTION customer magazine and publications in trade magazines since 2006.