Arecent discussion on the Microscopy Listserver on the subject of microtoming Si reminded many of us of this decades-old issue. Silicon is one of the easiest materials to prepare for TEM analysis with dozens of protocols available including chemical etching, electropolishing, mechanical polishing with and without ion milling, microcleaving, and the use of a focused ion beam instrument. The time involved in Si preparation can range from minutes to a few hours. Things become more complex if it is desired to prepare a Si semiconductor device with high specimen preparation spatial resolution i.e. prepping a prespecified, very small, structure.

Now and then a technologist, often times in the biological sciences, is asked to prepare a Si TEM specimen and wonders if Si can be microtomed. The results are almost always a pile of Si dust and frequently a damaged diamond knife.

Precollege science education in the United States is not what it could, and should, be. Major changes are being made in the way science is taught, but delivering those changes to thousands of schools is an enormous task. Scientific societies are a major resource; they can organize and train member-volunteers to help teachers bring “real” science to the classroom. The Microscopy Society of America has become part of the effort with Project MICRO (Microscopy In Curriculum - Research Outreach). MICRO is putting MSA members, teaching materials, and microscopes in middle school classrooms nationwide. The idea began in 1993, but it has taken a lot of time and effort to implement.

MSA's early decision to collaborate with experienced science educators at the Lawrence Hall of Science of the University of California at Berkeley was a wise one; their educational materials have a well-earned national reputation for excellence.

Attaching a sample to the instrument's sample stage is commonly the first step in the operation of an AFM. For our commercial Digital Instruments Multimode AFM, a sample is usually attached to a magnetic sample puck by double-sided tape, the sample puck is then placed on the instrument’s magnetic sample stage, and analysis can begin.

The use of double-sided tape, however, has unpleasant consequences. First, the surface of the sample puck becomes quite sticky due to residual glue from the double-sided tape ! removing the sticky glue is not a happy job. One cannot just throw a soiled sample puck away! Second, double-sided tape does not always give satisfactory mechanical stability during AFM operation, especially when high resolution imaging is being carried out. Sometimes the tape-mounted sample will creep slowly, which can cause significant drift of AFM images. This is because the tapes and their adhesive films are made of pressure sensitive materials that tend to change shape when pressure and/or temperature vary.

Excessive light to detectors can be very harmful. Too much light, either monochromatic or wide band, can easily destroy photomultiplier tubes (PMTs). Charge-coupled devices (CCDs) cameras, of modern design, are typically made with cut-outs so that saturation beyond several pixels will cause them to shut off. Unfortunately, the detectors in the back of your eyes do not have automatic shut-off mechanisms, and can be easily destroyed with excessive light.

As a review of filters and cubes, keep in mind that the primary job for the excitation filter is to block all light other than the desired band being used to excite the fluorochrome. The primary job of the emission filter is to block the excitation source. If these two optics are chosen correctly and inserted in the beam path, the only light reaching the detector is the fluorescence emission from the fluorochrome. Nothing from the source should make it to the detector. This very weak emission intensity has no chance of harming the detectors. If these two optics are not perfectly matched, the excitation light may reach the detector and cause all sorts of problems.

Osmium crystals tend to cling to the glass ampoule walls making dissolving them difficult. Smashing the vials results in glass shards that may get into sample vials and can be dangerous, or carry into embedding media and damage diamond knives.

A simple trick to eliminate smashing osmium vials is to dip the sealed ampoule into liquid nitrogen. This releases the osmium crystals from the glass walls. Then simply break the vial using an ampoule cracker (available through EM supply houses) and pour the osmium crystals into a bottle containing the water for the OsO4 solution. Wait a few minutes to let the ampoule warm-up, and it is easy to see if all of the crystals have been dumped out of the ampoule. Let the solution sit overnight at room temperature in a hood and the next day the crystals will be totally dissolved.