It was demonstrated 18 years ago that atoms could be manipulated, one at a time, on a surface. Yet only recently has the force required to move an atom been determined. Markus Ternes, Christopher Lutz, Cyrus Hirjibehedin, Franz Giessibl, and Andreas Heinrich, in a technical tour de force, have engineered a microscope that incorporates features of the scanning tunneling microscope (STM) and atomic force microscope (AFM) to accurately quantitate the lateral and vertical forces needed to move a single atom on a surface.

A key to understanding the function of biological systems is the visualization of their natural state, ideally in a natural environment. At a molecular level, this is challenging. Traditional experimental techniques, like X-ray crystallography, can provide the atomic structure of proteins, but only by removing them from their native surroundings and forcing them into crystals. Over the past decade, microscopy techniques have emerged as alternatives to these traditional structure determination methods, with the advantage of visualizing molecules in a near-native state. Given the current focus of structural biology on interactions between proteins and better understanding of large protein complexes, cryo-electron microscopy (cryo-EM) has become a valuable tool.

During the past several years, ASTM Subcommittee E04.14 on Quantitative Metallography has been developing an Image Analysis (I/A) methodology to determine the degree of circularity, roundness or sphericity of graphite nodules in ductile cast iron. In the as-polished condition, ideally the iron nodules should appear as dark circular objects in a light gray matrix, Figure 1. When performing Image Analysis measurements for these types of materials, complex gray image procedures should not be required to properly threshold the images to obtain an acceptable binary image on which to perform the measurements.

Biofilms are communities of microbial cells and extracellular polymeric substances (EPS) attached to a surface. Bacteria exist preferentially in the biofilm state in nature and in many engineered systems. In this state, microbes tolerate antibiotics and disinfectants. Bacterial biofilms are now implicated in a wide range of human diseases and infections including cystic fibrosis, otitis media, chronic wounds, artificial joint and prosthesis infection, and many nosocomial infections. Biofilm-related infections and industrial fouling problems cost billions of dollars each year.

“Extreme high-resolution” (XHR) scanning electron microscopy (SEM) has the potential to change the way we look at SEM. Anyone in the SEM world knows that you don't do high-resolution SEM at low accelerating voltages because of chromatic aberration limitations. The XHR design offers a new way to deal with chromatic aberration and realize the huge benefit of reduced beam penetration.

The new Magellan 400 SEM family is the first to offer subnanometer resolution over the entire electron energy range from 1 keV to 30 keV, effectively establishing a new performance category known as XHR SEM (Figure 1). To achieve this unprecedented performance, the Magellan combines novel electron optical design elements with technologies developed for the industry-leading Titan (scanning) transmission electron microscope (S/TEM) and DualBeam (focused ion /SEM) platforms.

Membrane proteins comprise the majority of known and potential drug targets, yet have been immensely difficult to analyze at the structural level due to their location in the membrane bilayer. Removal from the membrane necessitates replacement of the phospholipid bilayer by detergents in order to maintain protein solubility. However, the absence of lipids and the presence of detergents can render non-physiological conformational changes of the membrane protein (Tate, 2006). Electron crystallography is an important method for studying membrane proteins that usually takes advantage of reconstituting the protein in a phospholipid bilayer and removal of the detergent. Richard Henderson and Nigel Unwin used this technique to elucidate the three-dimensional (3D) arrangement of the transmembrane α-helices of bacteriorhodopsin, which was the first 3D structural information on a membrane protein (Henderson and Unwin, 1975).

Testing the mechanical properties of nanoscale materials faces a number of inherent challenges. As the size of the “target” decreases, the inability to actually see what occurs during testing can be troublesome. While a number of studies have attempted to characterize the mechanical response of nanoscale materials using traditional nanoindentation techniques, certain lingering questions have always remained. For example, the nature and sequence of failure events in the case of multilayer films has long been the subject of scientific debate. Similarly, in the case of individual nanoparticles, it is often difficult to ascertain that contact was both made and maintained throughout the test. Further, the crystallographic orientation of the sample and/or the presence of preexisting defects, which can have a significant influence on mechanical properties at the nanoscale, typically remain unknown.

Micro x-ray fluorescence (MXRF) is a microscopic analysis and imaging technique that is used to characterize the elements in a material non-destructively. Micro XRF instruments use an x-ray source to shine x-rays on a sample, and a detector to detect the characteristic x-rays given off. These fluorescent x-rays have very specific energies corresponding to specific electron energy transitions. Therefore, it is possible to detect and identify all of the elements present in a sample (typically above sodium) as well as measure their concentrations. This technique is widely used for the characterization of materials including polymer and metallic foams, powder samples, forensics applications, geological samples, works of art and nuclear fuels. Commercial MXRF instruments use a fused silica optic (mono or polycapillary) to focus the x-rays on the sample with no optic on the detector (Figure 1a).

Atom probe tomography has primarily been used for atomic scale characterization of high electrical conductivity materials. A high electrical field applied to needle-shaped specimens evaporates surface atoms, and a time of flight measurement determines each atom's identity. A 2-dimensional detector determines each atom's original position on the specimen. When repeated successively over many surface monolayers, the original specimen can be reconstructed into a 3-dimensional representation. In order to have an accurate 3-D reconstruction of the original, the field required for atomic evaporation must be known a-priori. For many metallic materials, this evaporation field is well characterized, and 3-D reconstructions can be achieved with reasonable accuracy.

Nature has provided us with a wonderful outer surface, the skin. We humans are fascinated with our epidermis and hair. We spend an exorbitant amount of time and money on skin and hair maintenance. We try hard to keep it soft, smooth, radiant, tan or pale, clean or made-up. We try to remove hair from some areas as hard as we try to keep it on others. Only when our skin is afflicted by disease, burns, wounds, or scratches is it apparent that this amazing outer shell protects us from dehydration and infections. To perform this crucial protective function and to be able to respond to injuries, skin needs to undergo self-renewal to repair damaged tissue and to replace old cells. For this formidable task, skin depends on stem cells. Stem cells have the ability to self-perpetuate and to give rise to differentiating cells that constitute one or more tissue types.

Most spectroscopies (FTIR, XRD, RAMAN, MS, etc.), were developed in order to identify materials. This is accomplished by capturing the spectral “signature” of an unknown and matching it to those of a comprehensive database of reference materials. Development of these spectroscopies has included efforts to embellish the associated database. EDS evolved as a resource to provide qual/quant, and development has been to improve the accuracy of quantation. Until recently, EDS was not considered a spectroscopy to provide identification of materials.

Cryo-fracture, in conjunction with critical point drying is a method used to prepare biological samples in order to expose, for viewing via scanning electron microscopy, those naturally occurring surfaces which might otherwise remain obscure. For example, the Bowman’s capsule and tubules of a kidney, tiny blood vessels on any organ, inter-cellular spaces in liver or alveoli in the lungs. Also, some surfaces, not normally exposed at all such as the membrane surface of a nuclear envelope, mitochondria or chloroplasts or the cytoplasm of a cell, can be brought to light with this method. Herein is a review of the development of cryo-fracture and how it is currently used at our facility.

Remote control of a scientific instrument is a topic gaining more and more attention between instrument users and operators. The project presented in this article reports results obtained from two distinct research efforts. The main outcome from the first research was the realization of an application to remote-control a Scanning Electron Microscope (SEM), while the main outcome from the second research was the implementation of a procedure to reconstruct 3D surfaces.

Coloring pictures is an educational exercise, which is fun, and helps develop important skills. Coloring SEM micrographs is especially suitable for electron microscopists. Color micrographs are not just great looking on a lab wall; they inspire both microscopists and students to exercise digital picture manipulation. Many microscopists enjoyed looking at the beautiful color micrographs by D. Scharf, but were frustrated to learn they needed a very particular scanning electron microscope equipped with multiple secondary electron detectors in order to color their own pictures. Fortunately, there are other ways to color SEM micrographs. Most SEMs are equipped with at least two detectors, for secondary and backscattered electrons.