A grant from the National Science Foundation will bring a new field emission scanning electron microscope (FE-SEM) to Colgate University, complete with a suite of high-tech detectors that will allow for new research in geology, physics, biology, computer science, and other fields.
“[The detectors] are incredibly versatile,” says primary investigator (PI) Martin Wong, professor of earth and environmental geosciences. “So many different things happen when electrons hit a surface, and you can use all those different signals to examine the composition and structure of your sample.”
The $439,805 grant is part of the NSF’s Major Research Instrumentation program. “The goal of the program is to support critical infrastructure for scientific research, but also to train students for high-level research,” Wong says. The equipment will benefit researchers throughout the central New York region as well.
Wong has partnered with several co-PIs on the project, including geosciences colleague William Peck and physics professors Ramesh Adhikari and Rebecca Metzler.
With a much smaller wavelength than visible light, electrons allow researchers to image vastly tinier objects than possible with an optical microscope. A researcher can get up close to see spores on a fern, hairs on the leg of a fly, nanowires that are a hundred thousand times thinner than the diameter of a human hair, or extremely small computer circuits.
Adjusting the magnetic field of the scope can train the flow of electrons in a variety of ways. “You can raster rapidly back and forth across a larger sample or fix it in a single spot to analyze something on the order of nanometers,” Wong says.
Wong’s own research focuses on plate tectonics of how mountain belts form and continents split. “When rocks are hot and deep, they don’t snap or break, but they actually flow like silly putty or saltwater taffy,” says Wong, who focuses his research on an area of the American West called the Basin and Range Province.
Wong analyzes samples with a special detector called an electron backscatter diffraction detector, which is able to show how crystals are oriented within it. “That tells us a lot about which directions they were stretching in, the temperatures at which they were doing that, and how deep inside the earth they were,” he says.
While Wong is mostly interested in basic science behind such processes, understanding them can also aid in earthquake detection and location of rare minerals.
Geology professor Peck focuses his research closer to home, examining the formation of rocks in the Adirondacks Mountains, Ontario, and New Jersey. He’ll be able to use the electron microscope to image samples with something called the secondary electron detector, which is able to display a graded map that differentiates between minerals.
For a more in-depth analysis, he’ll use an X-ray energy spectrometer, which can measure the degree that the electron stream excites the atoms within a sample, emitting X-rays that provide a fingerprint of which specific elements are contained within.
Adhikari, assistant professor of physics, works with organic materials. One project, for example, coaxes amino acids to self-assemble into tiny nanotubes; another threads nanoscopic computing components into the veins of leaves. “These bio-based materials tend to absorb the electrons that fall onto them, so you don’t really see that much,” Adhikari says.
That problem can be fixed by turning up the voltage of the beam, but that actually damages organic samples. The new microscope, however, can produce high-resolution images at very low voltage without damaging fragile organic components, allowing Adhikari to examine the tiny structures he is creating.
Among other uses, he is embedding the nanotubes into a polyester fabric to create a hydrophobic material that can filter oil from water. The leaves can be used to create biodegradable electronic equipment.
The ability to create crisp images at low voltage is also essential for Metzler’s work. The professor of physics studies biomineralization, the process by which marine organisms create shells and other hard materials. Some of her work examines exoskeleton formation by juvenile barnacles, which can be a scant 100 microns wide.
“Our current scanning microscope can’t resolve the crystals making up their exoskeletons,” says Metzler, who has previously had to make the 75-mile trip to Cornell to use its more advanced equipment.
She also studies other species of clams from the Gulf of Mexico, using the X-ray spectrometer to identify elements, and the backscatter diffraction detector to examine how crystals are oriented within shells in order to examine how climate change affects the durability of shells over time.
In addition to these research applications, the microscope will be used by a variety of faculty across campus, studying everything from volcanic eruptions in the Galapagos Islands to wear patterns of tools at pre-Hispanic archaeological sites.
The equipment is versatile enough that it can be used in classroom demonstrations as well as the lab, says Wong. Countless students will use it for thesis projects over the next couple decades; at the same time, exposure to the advanced instrument will help students gain experience that could help them in working with microprocessors, nanotechnology, or mining.
“This is a broadly used piece of equipment with all sorts of research and industry applications,” Wong says. “Being trained on it will give students a leg up no matter what avenue they pursue.”