Laser tweezers take advantage of the forces around converging beams of light to exert slight pressures on small structures. Whereas these optical devices have allowed for some elegant studies of cell biology, wouldn't it be great if we had mechanical tweezers that offered even better manipulation? In a recent paper, Philip Kim and Charles Lieber demonstrated a fabulous device they called “nanotweezers.“

Logically, they used nanotubes as the key structural component for their nanWith nanotubes serving as the tines of the tweezers, Kim and Lieber devised a very clever arrangement for the hub. They took a standard glass tube, 1 mm in diameter, and pulled it to a tapered end of about 100 nm.otweezers. Carbon nanotubes are particularly strong for their size, they conduct electricity, and they can be fabricated as small as 1 nanometer (nm) in diameter. With nanotubes serving as the tines of the tweezers, Kim and Lieber devised a very clever arrangement for the hub. They took a standard glass tube, 1 mm in diameter, and pulled it to a tapered end of about 100 nm. They then evaporated a very thin coat of chromium and then gold on one side, then rotated the rod 180° and deposited metal on the other side. Each coated side operated as an independent electrode.

Photographic chemistry has long been a complex combination of inorganic metal-halide and organic chemistries and polymer science. We at the P.R.I, have managed to add biology to this stew.

Silver has long been known as a toxicelement to microbes, and so used as a drug to kill bacteria. But there are bacteria that can survive in environments high in silver. It has been reported that some bacteria can accumulate up to 25% of their dry biomass as silver, and so acquire resistance to the toxic effects of silver. Also, a recent article in the Proc. Nat. Acad.Sci. describes the intracellular deposition of silver grains in such shapes as hexagons and equilateral triangles.

To successfully isolate 1-100 μm samples for microscopical examination or analysis, one needs a good set of microtools, with the most essential being the needle and the micropipet. This paper will describe how to make them and how they are used to solve various sample preparation problems.

After an inquiry from the Microscopy Listserver, I went back to my 1980 copy of Scanning Electron Microscopy, volume I. Several authors had investigated the structure of thin metal films by depositing the films onto carbon-film-covered TEM grids and imaging the films at high magnification. There were several proposals for new devices that have since become standards for high-resolution coaters, but the Listserver inquiry was for a fine conducting film suitabie for high-resolution SEM from an existing sputter coater.There were several factors studied that influenced the fine structure of the films. The first was the materials sputtered: for a given set of conditions of voltage, current and time, platinum gave the finest film, 60% gold-40% palladium (Au/Pd) the next finest and pure gold the least fine.

Ready or not, digital imaging in the microscope lab is here to stay. While I am one of those fogies who insist that digital images are nowhere near as good as photographic prints, I've also bowed to the inevitable, and begun to find ways to assist clients in our multi-user facility with their digital imaging needs. We can acquire digital images from our FESEM, with a CCD camera on our EFTEM, from our light microscope with a CCD, and from a flatbed scanner. Clients use their images for image analysis, transport to others scientists via the Internet or World Wide Web, for reports, slides, overhead transparencies, and publication. Generally, these images need to be manipulated for use, just as one wouid manipulate a photographic print in the darkroom to correct any deficiencies in exposure or area of view.

Recent advances in cameras and computers have made it possible to build electron backscattering diffraction (EBSD) cameras which can give crystallographic information from specimens in the scanning electron microscope (SEM) on a routine basis. There are a few hundred such systems world wide and the number is growing fast. In the case of crystalline samples (nearly all applications of SEM outside the biomedical field), it will surely soon be considered essential to fit an SEM with an EBSD system, just as it is now considered essential to have the SEM equipped with an energy-dispersive x-ray spectroscopy (EDS) system. There are at feast four commercial manufacturers of EBSD systems.

It has become increasingly obvious that infrared microspectroscopy can be the analysis tool of choice when determining the chemical composition of biological and biomedical samples. Frequently, fluorescence illumination is required for sample characterization, which previously required the use of a separate optical microscope. There has also been a need in the semiconductor manufacturing industry for a single tool for visualizing particle contaminants on integrated wafers as well as the ability to chemically determine their nature. There is now a single microscope platform for conducting rapid Nomarski differential interference contrast and fluorescence illumination sample visualization as well as infrared analysis. This novel infrared microscope has applicability to many fields of investigation, including pharmacology, forensics, cell biology, histology, gemology, and geology.

Monte Carlo simulation of electron scattering in solids has proven valuable to electron microscopists for many years. The electron trajectories, x-ray generation volumes, and scattered electron signals produced by these simulations are used in quantitative x-ray microanalysis, image interpretation, experimental design, and hypothesis testing. Unfortunately, these simulations are often computationally expensive, especially when used to simulate an image or survey a multidimensional region of parameter space.

Here we present techniques for performing Monte Carlo simulations in parallel on a cluster of existing desktop computers. The simulation of multiple, independent electron trajectories in a sample and the collateral calculation of detected xray and electron signals fall into a class of computational problems termed “embarrassingly parallel”, since no information needs to be exchanged between parallel threads of execution during the calculation.

Control of layer thickness is critically important in the manufacture of semiconductor devices. Cross-sectioning exposes device structures for direct examination but conventional sample preparation procedures are difficult, time consuming, and grossly destructive. Cross sections created by focused ion beam (FIB) milling are easier, faster, and less destructive but have not offered the clear layer delineation provided by etching in the conventional sample preparation process. A new gas etch capability (Delineation Etch™ from FEI Company) offers results that are equivalent to conventional wet-etch preparations in a fraction of the time from a single, automated system in the fab without destroying the wafer. The new etch process also has application in milling high-aspect-ratio holes to create contacts to buried metal layers, and in deprocessing devices to reveal silicon and polysilicon structures.

A central theme of modern materials science has been the exploration of the relationship between the microstructure of a material and its macroscopic properties. Beginning in the late 19th century, the developing field of metallography permitted scientists to view the microstructure of metal alloys. Mechanical polishing followed by selective chemical etching produced differential relief on chemically distinct phases or at grain boundaries. With such specimens, reflection optical microscopy revealed structures with micrometer and even finer dimensions. The microstructural world that was found proved to be highly complex, and most alloys were observed to be chemically differentiated into two or more distinct phases.

The resurgence of microscopy in recent years is certainly not news to readers of this journal. But, for many of us, this resurgence has placed additional strains on our already busy lives to keep current on new technologies and techniques. Fortunately, books such as “Imaging Neurons. A Laboratory Manual” (Edited by Rafael Yuste, Frederick Lanni and Arthur Konnerth) provide comprehensive and timely reviews to help us keep abreast of the field.

The book evolved from a summer course taught by the editors and many of the contributors at the Cold Spring Harbor Laboratory, and although it obviously targets neurobiologists, many of the techniques are applicable to other biological systems. An impressive feature of the manual is the breadth and detail of topics covered.