Low-voltage Transmission Electron Microscopy Research Articles

Use of the Low Voltage Transmission Electron Microscope with Biological Specimens: A Feasibility Study

Abstract Biological transmission electron microscopy (TEM) has evolved over the past 50 to 60 years in concert with the instrumentation available. As beam acceleration energies have increased to 100-200 keV, specimen preparation protocols have been modified and tailored to fit the capabilities and constraints of new TEMs. Higher voltage allows improved resolution, (Fig. 1) but as acceleration voltage increases, contrast decreases. Vacuum levels required for conventional TEM prevent specimen contamination which protects specimen details from being obscured, but lower contrast requires heavy metal post staining which may lead to specimen contamination. Specimen thickness can increase with higher voltage (up to lOOnm at 200keV) because penetration is much increased, however, the chance of specimen - electron interaction of the type that causes heat build-up and specimen damage increases rapidly with thickness. It seems that these limitations and others must be tolerated in order to enjoy the obvious advantages of TEM.

Low-voltage TEM imaging of polymer blends

Low-voltage transmission electron microscopy (LV-TEM) was applied to obtain images of the phase structure of selected polymer blends without any prior staining. The instrument used (LVTEM-5, working at 5kV) is of a novel construction combining visual-light and electron-microscopical techniques, resulting in an enhanced efficiency of light transport to the eye and facilitating CCD imaging. Results were compared with LV-STEM at 25kV. Phase structure of polycarbonate/poly(styrene-co-acrylonitrile) (PC/SAN), polystyrene/polypropylene (PS/PP), and polyethylene/polypropylene blends (PE/PP, ADFLEX) were selected to demonstrate the above techniques. The difference in density between the individual components of polymer blends was found to be the reason for the obtained image contrast. Differences less than 0.04g/cm3 can be traced with this technique.

Reflection Holograms Formed Using Polymer-Dispersed Liquid Crystals

The electrical switching characteristics of reflection gratings formed using polymer-dispersed liquid crystals are explored. First, an explanation for the lack of switching in previously formed gratings formed using E7 as the liquid crystal is proposed based on experiments on slightly slanted gratings. These confirm that the LC director orientation within the anisotropically-shaped LC domains is parallel to the grating vector(and applied electric field direction). Slight modification of the syrup leads to transmission gratings with different polarization dependencies and reflection gratings (non-slanted) that switch completely with a modest electric field. These differences are attributed to a 90° rotation in the preferred LC director orientation within the LC domains. This change in orientation results in strong coupling of the electric field with the LC dipoles in a reflection geometry thereby leading to easier switching. The microstructure of these grating structures are explored using low-voltage scanning electron microscopy and bright-field transmission electron microscopy.

A Novel Technique to Determine Platelet Deposition on an Experimental Nylon Membrane Using Lvsem and Tem

Abstract Porous nylon fabric is used as a filter in blood devices. This study was undertaken to evaluate the interaction between an experimental nylon filter and the cellular elements which pass through it. Our investigation was mainly centered on determining the deposition of cellular material on the nylon filter using Low Voltage Scanning Electron Microscopy (LVSEM) and Transmission Electron Microscopy (TEM). The filter was prepared for LVSEM by cutting a 2.5 cm2 of the nylon filter material with a razor and placing it in a nylon mesh bag which was stapled shut. The bag was rinsed three times for ten minutes each in fresh Sorensen's phosphate buffer. A graded alcohol series of 25%, 35%, 50%, 70%, 80%, and 90% was used to dehydrate the filter for ten minutes each. This was followed by dehydration twice for 20 minutes in fresh 100% ETOH. The filter was then Critical Point Dried (CPD) in the Tousimis AUTOSAMDRI-814.

Recrystallization mechanisms in commercial A1–2Mg alloy

AbstractThe mechanism of nucleation of recrystallization is described for material having either a hot worked substructure or a cold work structure. Experiments have been conducted using low and high voltage transmission electron microscopy including in situ observations in the high voltage microscope. Salt bath experiments have been conducted to confirm the results. It is shown that recrystallization of hot worked structures involves subgrain coalescence followed by boundary migration. In the alloy investigated the dissolution of the β phase was important in creating a dislocation free region. The recrystallization of cold worked structures involves the creation of subgrains about the same size as in the parent hot rolled material, dislocation activity to form a medium angle boundary, and the migration of this boundary to form a high angle boundary and the recrystallization nucleus.

Utilisation de coupes sériées épaisses en microscopie électronique à transmission à basse tension pour la reconstitution tridimensionnelle de microorganismes parasites intracellulaires de végétaux

SummaryThe observation of thick sections, series of thick sections and stereopairs taken from these sections, under low voltage transmission electron microscope, had proved useful in reconstituting Mycoplasma-like-organisms found in sieve elements of yellowed Vicia faba. Spatial reconstitutions provide informations about the organization of the microorganisms.

A new preparation method for large area electron-transparent silicon samples

A technique for the preparation of large area (several millimetres in diameter) samples is described, which can be applied to both low and high voltage transmission electron microscopy (TEM). The procedure starts with chemical thinning down to 2-10 mu m from one side of a whole silicon wafer. From the thinned wafer, discs of a diameter suitable for the TEM examinations are chemically separated by a photoresist step and are fastened onto a metal ring adapted for the TEM sample holder. For low voltage electron microscopy these silicon discs must be thinned to less than 1 mu m in a further chemical treatment.