New Era Heralded for Resolution and Sharpness

STED sharpens up microscopic
insights; © Max-Planck-Institut

Max Planck researchers have succeeded in overcoming the law postulated by Ernst Abbe in 1873 for diffraction limited resolution in light microscopes. Stefan Hell and his co-workers have established a new law that promises unlimited resolution in fluorescence microscopy.

Future applications range from the imaging of cell interiors to the measuring of lithographic structures in microchip manufacturing, and substantial improvements in the quantification of the reaction kinetics of organic molecules.

For a long time, Abbe's law was regarded as being insurmountable. However, over the past few years, researchers from the Max Planck Institute for Biophysical Chemistry in Göttingen, Germany, have developed with Stimulated Emission Depletion (STED) microscopy, a physically consistent concept for breaking the diffraction limited resolution limit in fluorescence microscopy, and then verified it in experiments.

Unlike in the light microscopes conceivable so far, in a STED microscope, the relevant focal fluorescence spot can, in principle, be reduced in size to the size of a molecule (2-5 nm). This is due to the fact that the spot size is no longer subject to Abbe's formula, but to a new law that differs from Abbe's original formula in a crucial factor - a square root term:

In one of their latest publications, the Göttingen-based research team verifies this new law with their experiments. They show that even with conventional objectives and focused light, resolutions of 16 nm are feasible. Therefore for the first time ever, it has been demonstrated experimentally that even with focused-light optics, resolutions at the nano-level are possible in fluorescing samples.

In an additional publication, the researchers show that STED microscopy allows one to image lithographic structures of width as small as 40-80 nm, a size previously reserved for electron microscopy.; Source: Max Planck Society for the Advancement of Science