Anja Schué: Optical microscopes reveal the nano-world

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.

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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.

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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.

Anja_SchueThe 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.