Innovative Electron Microscopy
Nanoscale characterization is essential for the growth of modern nanotechnology, energy science, biology, and biomedical sciences. The Program Division Innovative Electron Microscopy conducts interdisciplinary research at the interface of physics of electron microscopy, biophysics, materials science, cell biology, and image processing. We develop forefront in situ transmission electron microscopy (TEM) and scanning TEM (STEM) methods for the study of functional materials and biological systems at realistic conditions, with a focus on liquid-phase electron microscopy. We are also exploring new routes for three-dimensional (3D) data acquisition using intelligent STEM- and image reconstruction strategies. We have extensive experience with image processing and particle detection methods, and with developing protocols for specific labeling of proteins with nanoparticles. Various research collaborations exist both with academia, and industry. Students and users obtain high-quality training on modern electron microscopy in our group.
The INM houses a state-of-the-art aberration corrected STEM/TEM of the type ARM200, JEOL, Japan, with a combined energy filter and an electron energy loss analyzer (Gatan). This microscope has a cold field emission source (CFEG) with low energy spread. The microscope combines a spot size of 0.08 nm with a probe current of 200 pA and an energy spread of only 0.3 eV. This microscope is used for various areas of research at the institute and also at the Saarland University.
We have developed a novel STEM technology to image whole eukaryotic cells in their native liquid state, so-called Liquid STEM, based on the technology of liquid-phase electron microscopy. Proteins are specifically labeled with electron dense nanoparticles. The atomic number (Z) contrast STEM is then used to image the nanoparticles within a layer of liquid containing the cells. Labels of different sizes and compositions can be distinguished. The Liquid STEM is combined with fluorescence microscopy using proteins labeled with quantum dots. Liquid STEM is also used to study nanomaterials in liquid. More information.
Our research aims to study the role of epidermal growth factor receptors in cancer cells. Of key interest is to analyze differences in protein function between individual cancer cells (cancer cell heterogeneity) and between distinct functional membrane regions within the same cell. With our approach it is possible to study the effect of cancer drugs on small sub-populations of cells, aiming to increase the effectiveness of HER2 targeting drugs. This research is funded by the Else Kröner-Fresenius-Stiftung. More information.
Together with Prof. Barbara Niemeyer, Molecular Biophysics, Saarland University, Homburg, Germany, we explore the stoichiometry of ORAI Ca2+ channels. This research is funded by the Deutsche Forschungs Gemeinschaft and is part of the Collaborative Research Centre 1027 entitled “Physical modeling of non-equilibrium processes in biological systems”. More information.
TEM and STEM of liquid specimens offer unique options to study the nanometer-scale dynamic processes occurring at liquid interface. New fundamental insights are gained in nanoscale dynamics, and local van der Waals interactions. We discovered that nanoparticles in close proximity of a surface do not move as predicated by Brownian motion but many orders of magnitude slower. More information.
We are partner in the MARIE SKLODOWSKA-CURIE ACTIONS Innovative Training Network (ITN) project “A multiscale approach toards mesostructured porous material design, MULTIMAT”, headed by Prof. Nico Sommerdijk of the Technical University of Eindhoven, the Netherlands. This consortium uses in-situ analysis to unravel the mechanisms of multiscale assembly. More information.
We are developing a novel methodology to acquire 3D data sets using aberration corrected STEM. The primary method currently used for obtaining nanoscale 3D information of materials is via tilt-series TEM. A novel approach uses aberration-corrected STEM, which is capable of high-resolution 3D imaging without a tilt stage. In a manner, similar to confocal light microscopy, the sample is scanned layer-by-layer by changing the objective lens focus so that a focal series is recorded. We combine both tilt- and focal series acquisition to obtain the best possible 3D reconstruction. More information.
Research projects are conducted together with scientific partners in the areas of functional nanomaterials, and of energy-related materials, such as solar cells, solid-state lighting elements, and catalytic materials. The properties of functional materials are closely related to the atomic structure and especially dislocations of atoms within the bulk structure, and at interfaces. Aberration corrected STEM is capable of atomic-resolution chemical mapping using EELS, X-ray elemental analysis, and Z-contrast, such that dislocations of single atoms can be studied within the atomic matrix.