Cornell Center for Materials Research (CCMR)
Soft samples need to be cooled for the microtome, a tool used to cut very thin sections of a material. Graduate student Michael Zachman from the Kourkoutis group prepares a soft sample of biological material by freezing it with liquid nitrogen. Soft samples such as biological materials are almost impossible to slice. Freezing soft matter makes it glassy, which makes it easier to slice off a thin piece for imaging. Zachman places the sample on a small screw-like sample holder, which will later be placed into the microtome for cutting.
“You can think of the microtome as a microscopic meat slicer,” says Jonathan Shu, CCMR associate director. “Researchers make very thin sections of material, measured in nanometers, thin enough to image in the transmission electron microscope (TEM).”
The blade of a microtome is made out of diamond or glass, and it moves in a guillotine-like motion relative to the sample. The cryomicrotome is like a regular microtome with the addition of cryogenically freezing the sample while it is cutting. The blade moves closer and closer to the sample until it eventually takes a thin slice. Samples need to be very thin because for microscopic examination; the TEM shoots electrons through materials to image them. Once there is an appropriate sample, a researcher can pick it up with cold tweezers and transfer it to a microscope.
A student operates the cryomicrotome. A close-up of the inside of the machine shows a frozen sample getting sliced. Like prepping samples, the cryomicrotome uses liquid nitrogen to keep samples cooled at -175°C.
This polishing tool is a way to create samples for the transmission electron microscope (TEM). Instead of slicing off a thin section, as with the microtome, this tool allows researchers to start with a thick piece and polish it down at an angle to create a wedge. At the end of the wedge, there is a very thin section of film only a few atoms thick. With that section, researchers can conduct TEM imaging. Most materials researchers use this tool prior to using the TEM, polishing hard material samples, such as ceramics, glass, and metals.
Here, Don Werder, CCMR Electron Microscopy Facility Manager, uses the tool to grind and polish a hard material sample.
“The most important thing to the CCMR is staff experience” Shu says. For example, CCMR Electron Microscopy Facility Manager John Grazul (pictured here) is an expert in sample preparation. “Without his knowledge of how to prepare samples, soft samples, and biological samples, one will never get a good electron microscope image.”
The CCMR employs ten staff Facility Managers, who are experts at using the center’s various instruments. CCMR facility users attend training sessions run by Facility Managers.
The transmission electron microscope (TEM), in 150 Duffield Hall, is used to analyze inorganic and organic materials at the nanoscale, with a resolution of about two nanometers. The TEM works by shooting a beam of electrons at a very thin sample material. The electrons move through the specimen, which allows the microscope to capture a highly detailed image at the atomic scale. Researchers in the physical and life sciences use the TEM to image materials, from biological samples to new nanomaterials.
The TEM shown here is equipped with a camera, detector, analysis and imaging software, and an x-ray detector. The x-ray detector makes it possible for the TEM to also do elemental analysis by letting the sample generate x-rays and detecting what types of x-rays are emitted.
The Focused Ion Beam (FIB), in 150 Duffield Hall, images a material like a scanning electron microscope but instead uses heavy gallium ions instead of electrons. The ions can do more than just image the material. They can also etch away at the material, allowing a researcher to surgically cut trenches and to even form thin cross sections in order to prepare samples for the transmission electron microscopes (TEM). Organic, inorganic, and novel materials are not always amenable to conventional TEM sample preparation methods, so the FIB system is useful for such materials. Most importantly, the FIB can make a TEM sample from a site-specific location. A cryogenic stage in the FIB also allows researchers to freeze a soft sample—a liquid or gel—cut it with the FIB, take it out frozen, and put it into the TEM for further imaging.
Graduate student Yimo Han prepares a TEM sample. The top monitor shows that there are craters that have been etched out of the material by the FIB. The system also has microtweezers in order to pick up cutout sections for use in the TEM.
Next to the FIB is another sample-prep station, used for cryogenic samples. Lena Kourkoutis’s group is the main user of the station. Her lab can freeze samples at the station and load it into the FIB’s load lock in the cold stage. Behind and around the FIB system is red foam that can absorb noise and vibrations, so as not to disturb the instrument.
The Cornell Center for Materials Research (CCMR) supports interdisciplinary materials research and development at Cornell, hosting more than 100 faculty members from four colleges, who work on a variety of projects. The center currently supports three Interdisciplinary Research Groups (IRGs): Atomic Membranes; Controlling Complex Electronic Materials; and Mechanisms, Materials, and Devices for Spin Manipulation. Through several seed grants, the CCMR also supports high-risk research, such as work on 2D quantum dot solids and the formation of hybrid organic/inorganic materials. Much of the research takes place at CCMR’s Shared Facilities, which includes a main prep lab and several microscopes located at Duffield Hall, as well as other labs in Bard, Clark, Snee, and Olin Halls. The facilities offer world-class materials analysis and processing equipment and are overseen by a staff of experts.