With this Microscope, Seeing Is Believing, Virtually by Anne C. Paine | photos by Al Fuchs January 6, 2003     With components that fill a small room, Oberlin’s new scanning electron microscope looks nothing like a conventional light microscope. The first clue that this is no ordinary microscope is that there's no eyepiece. Instead, the machine is a complicated arrangement of white-enameled metal boxes, tubes, and knobs, with an attached silver cylinder that looks rather like a two-foot-tall steel thermos. Then there's the related apparatus—a computer and two large screens. The four components cover the surface of a standard office desk. This sleek machine is Oberlin's new scanning electron microscope (SEM), an extremely high-tech tool that allows scientists to view specimens at the microscopic level. The College purchased the microscope last year with the help of a $100,000 matching grant from the National Science Foundation (NSF). So just how powerful is this instrument? Consider this comparison: traditional optical (light) microscopes, such as those found in biology teaching laboratories, magnify about 1,000 times. The scanning electron microscope magnifies up to 200,000 times. Talk about detail! "I've heard this analogy used to describe the magnification: It's like being in a jet plane at 30,000 feet and seeing the individual roof shingles on the houses below," said Jonathan Castro, assistant professor of geology and principal investigator for the grant.   The scanning electron microscope can give researchers a wealth of information. The three computer screens shown here offer different types of information about a sample of obsidian (volcanic glass) being studied by Assistant Professor of Geology Jonathan Castro. The small screen on the left shows an infrared image of the sample in the vacuum chamber. The middle screen shows a scanning electron photomicrograph image from which Castro can draw qualitative information. The screen on the far right displays a quantitative analysis, or compositional breakdown, of the obsidian. Two pieces of obsidian—one polished and the other rough—are on the desk in front of the screens. See images captured by the microscope >   The microscope recently was installed in its office on the second floor of the Carnegie Building, and it is now being calibrated and its settings fine-tuned to ready it for use by faculty members and students. Plans call for the microscope to be used in hands-on experiments in more than a dozen geology, chemistry, biology, and physics courses, from the introductory to the advanced level, probably starting next year. Within two years, it is expected that 600 students will have used the microscope in course work and independent research. "A major selling point with the NSF was the interdisciplinary approach we took in our grant application. It was something unique that they hadn't seen before," Castro said. Oberlin acquired its first scanning electron microscope about 15 years ago, but the new instrument is far more advanced and easier to use. In addition to its amazing imaging capabilities, the new SEM will enable students to conduct qualitative and quantitative elemental analysis of a variety of specimens, including minerals, microfossils, semiconductors, plankton, pollen, and synthetic crystals. Preparing samples for the new SEM is easier than with the old instrument, and the computer's user-friendly interface allows novices to gain proficiency with the instrument quickly. The SEM doesn't really produce an image of the specimen, but rather it digitally captures a virtual image of the specimen. Yolanda Cruz, professor of biology, has used scanning electron microscopy in her work since the mid-1980s. She explained how the SEM works. "The specimen to be examined is placed in the special chamber, which is evacuated (rendered a vacuum). Otherwise, the electron beam used to ‘see' the specimen could not be produced—air molecules would interfere with its flow. The SEM generates an electron beam that is directed at the surface of a specimen, for instance, a pollen grain. The electron beam scans the surface of the pollen grain, much as a searchlight would. The beam hits the surface of the pollen at many different points and flies off in many directions, like marbles hitting a rough floor. "A transducer mechanism in the SEM collates all these bounced-off electrons, records their individual trajectories, and composes a two-dimensional, black-and-white digital image. Because the trajectories are dependent on the elevation of the point at which the beam hit the pollen surface, the collated trajectories show the fine gradations in microtopographic features of the pollen grain itself. This is the image that the SEM produces—it's really not an image of the pollen, but rather of a virtual object that is based on the dimensions and physical features of the pollen. Because electrons are very, very small, SEM beams are able to access very, very small spots on the pollen grain, and the image produced is one with an extremely fine resolution." Faculty members began adapting curricula to include use of the SEM during winter term and will continue that work next summer, Castro said. Beginning last January, an annual winter-term course taught by Castro and Cruz will teach interested faculty members and students to use the SEM.