What a Difference a “T” Makes

STEM replaces SEM for science investigation

Nancy Murray's and David Johnson's BOMI 103 Biology of Cultivated Plants class comes in each semester to image pollen that they collect from a variety of flowers. (Photo courtesy of Laura Tuhela-Reuning)

Last May, Ohio Wesleyan received a new Zeiss EVO® LS10 SEM ATLAS Scanning Transmission Electron Microscope (STEM). This instrument, located in room 157 of the Schimmel/Conrades Science Center, replaced the former scanning electron microscope (SEM) that had been there since 1997. “I knew there were limitations on [the old SEM],” says Laura Tuhela-Reuning, scanning electron microscope technician and professor of botany/microbiology and zoology. “The software was getting old. Nobody keeps a computer around for 14 years.” So Tuhela-Reuning, along with fellow zoology professors Ramon Carreno and Jed Burtt, as well as geology professor Karen Fryer, wrote a grant proposal to the National Science Foundation to request the funding to purchase the new STEM.

Unlike the SEM, the new STEM is able to image slices of material that are only nanometers thick. To visualize nanometers, consider that a human hair is approximately 60,000 nanometers thick; a millimeter contains one million of these tiny units of measurement. This level of magnification enables students and faculty to look at the ultrastructure of a cell to see what’s inside and where it’s located.

A camera inside the vacuum chamber allows the student to see the sample on the stage while it is being imaged, so he or she can visually monitor how close the sample is to the detector when repositioning it, making it easier to avoid hitting the detector.

The new STEM also has an energy dispersive spectrometry system that can determine what elements are present in a sample. “This is particularly useful for geologists, but biologists have made use of it as well,” said Tuhela-Reuning. Although the older instrument also had this capability, the STEM instrument is more efficient and provides much better resolution.

The availability of this technology affords OWU students a unique opportunity. “It is very rare that undergraduates anywhere have access to a STEM, let alone the opportunity to operate it themselves,” says Tuhela-Reuning. In most universities, if the students have access to such an instrument, it is operated by technicians and the students never get to actually touch the controls, but “when [OWU] students get to graduate school, they haven’t just learned about it in a book—they’ve actually done it themselves,” she says.

Zoology majors use the STEM to observe various parasites as well as the different stages of zebrafish embryo development. Along with microbiology students, they also investigate how feathers are affected by bacteria. Plant biology students use the microscope to observe leaf and pollen samples, and the interactions between leaves and fungi. Geologists have used the STEM to determine where various elements are located within thin sections of rock, giving them insight into the conditions under which the rock formed.

So what happened to the scanning electron microscope that OWU students and used for so many years? “It’s like a trade-in; when you trade in a car and you get a new one,” says Tuhela-Reuning. “I understand the company has it up and running in their facility in Boston.”

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