Gallery of electron images by SEM class students

electron image of sand

Low magnification image of sand illustrating how images taken at long working distances with very low energy electron beams tend to distort around the edges.  Increasing the energy (keV) of the beam would correct this problem completely.  Dakota Pittinger - an exceptional paleontologist! - took this image during his systematic study of how changing working distance affects image quality. (7.9 Mb image)

Applied Scanning Electron Microscopy class

Some students want more complete training in electron microscopy.  They want to learn the underlying physics and chemistry of how the SEM works, how to communicate analytical conditions, and learn how to:

The images on this page are solely ones taken by undergraduate college students in my Practical Scanning Electron Microscopy course at Kutztown University.  Please click the images to see the figure captions that explain the image and have links to the full-resolution images iconized by the thumbnail images.  

Please remember: all of these images were taken by undergraduate college students in the course of learning to operate the SEM - not by professionals with lots of experience.  You might see some scan errors due to charging or a contrast/brightness that's not what you might choose, and that should be expected because these are students who took these images while learning.  These are just routine images students took in the course of their training, not final-product.  In retrospect, I should have assigned students to take a best-they-can-do image to showcase their skills learned, but hindsight is 20:20.  We can do that this semester!

Note: these are also just the jpg versions of the images - the tif images retain even more detail!

Sweet beginning for
Fall 2023 class

This is one of the class's first two images of the semester.  It's sweet to see students succeed and gain skill so rapidly.  These are common table sugar crystals (sucrose) viewed at low magnification.  The class did a great job with their focus, brightness, and contrast.  They used a 3 keV beam because they wanted a low magnification image with minimal spherical aberration (blurring around the edges) while maintaining good surface detail.  The crystal in the center looks orthorhombic, but it's actually monoclinic (a-axis is actually slightly inclined relative to b and c).   The sample is coated with Au to avoid charging.
(1.4 Mb image).

Previous classes

Anthony Rulavage's image of a megalops (larval) stage of a crab

Megalops (larval) stage of a crab 1

Anthony Rulavage was a marine science major interested in imaging the megalops (larval) stage of a crab. These little critters have jointed exoskeletons, so he had a tricky time mounting them without legs breaking off, etc.  He persisted, though, and took these low-magnification images of the larvae.  (2.1 Mb image)

Larval crab face (scary monster?)

Megalops (larval) stage of a crab 2

Anthony Rulavage's facial portrait of a larval crab.  If crabs weren't r-strategist species, this little creature's face might have been one that only their mother loved (or maybe this is the Apollo/Aphrodite of their generation!). (2 Mb image)

synthetic polymer with conchoidal fractures

Samantha Evans's polymer 1

Samantha Evans is a chemist and is easily one of the most impressive scientists I've ever met, and I'm not just including students in that assessment - that's compared to all scientists I've known.  She's exceptionally curious, asks precise questions, creatively generates multiple hypotheses and experiments to test them, executes research with phenomenally meticulous precision, and thinks about what her results mean.  She inspires me, even a couple years after she's graduated.  These images are of some sort of polymer she made with Dr. Lauren Levin (a great colleague here at Kutztown University). (3 Mb image)

synthetic polymer with conchoidal fractures

Samantha Evans's polymer 2

Sam did a great job with these images.  The polymers are electrically non-conductive, so there is a danger of building up charge that would distort the image.  Typically, people coat non-conductive samples with metal (gold or platinum) or with graphene carbon, but Sam wanted to image these without coating.  She wanted good shadowing, so she used the chamber secondary electron detector (Everhart-Thornley) and dialed the electron beam energy down.  The image on the left used a 0.5 keV beam (a very light touch), so she kept a short working distance, but made sure to orient the sample so this face pointed toward the detector, which gave her a bright signal in spite of the potential shadowing from the pole piece.  The low energy beam not only helps avoid charging, but also limits the signal to the topmost surface so gives outstanding surface detail. (3.2 Mb image)

TEM image of mouse brain cells

Mouse brain cells 1

Devin Peterson is a neurophysicist and a software engineer and a physically really fit guy and a great soul.  Devon wanted to see mouse brain cells using the Scanning Transmitted Electron Microscope (STEM) detector.  We do not have uranium-staining or ultramicrotome (slicing) facilities, so, sua sponte, he found a TEM lab who gave him some old samples.  His are some of our first images with the STEM detector. (3.1 Mb image)

TEM image of mouse brain cells

Mouse brain cells 2

Transmitted Electron Microscope (TEM) samples are made by stabilizing the cell tissues, then staining them with uranium to give them electron contrast, slicing them with an ultra-sharp diamond blade into 100-nanometer thick flakes that must be positioned on a 3-millimeter diameter metallic grid covered with an ultrathin polymer base.  Devon used the binocular microscopes to position and load samples because 3 millimeters is the size of a typical freckle. (2.9 Mb image)

TEM image of mouse brain cells

Mouse brain cells 3

Devin Peterson got pretty good with the STEM detector.  This image entire is 4.13 micrometers wide (that would be one six-thousandth of an inch).  The period at the end of this sentence is about a half millimeter in diameter.  Over a hundred of this image could be placed side-by-side across this period.   (11.8 Mb image)

TEM image of mouse brain cells

Mouse brain cells 4

The samples were pretty old, so the ultrathin polymer sheet was torn in many places.  This created an imaging problem because the broken sheet flapped under the electron beam like a flag in the wind.  Devon had to find the lease torn parts of the sample, and use several image-stabilizing tricks to get these images.  Note that he thought to lighten the beam energy to 22 keV to reduce movement of the sample.  Devon is a very smart (and good!) guy. (2.8 Mb image)

TEM image of mouse brain cells

Mouse brain cells 5

One of the challenges for me as an SEM instructor is learning what people see in their samples.  The last time I took a class in biology was 1986 or so.  Maybe the blobs on the right are mitochondria and dark dots ribosomes?  Definitely not rocks!  (3 Mb image)

TEM image of mouse brain cells

Mouse brain cells 6

Devin found a lot of different kinds of organelles in these cells.  Those that have strongly-contrasting dark edges are features that absorbed and retained more of the uranium stain (which is opaque to electron beams).  I hope someone in this semester's class wants to do more STEM imaging! (3 Mb image)

spotted lanternfly nymph head

Spotted lanternfly nymph 1

Grace Hetrick is now a working in the environmental geology here in Pennsylvania, making the Commonwealth safe for the citizens.  She was interested in imaging spotted lanternfly nymphs because they're an invasive species here and of concern to ecologists.  This is an image of the back of the head of one of the nymphs.  The feature in the foreground is some sort of chemical sensor, and the segmented eye is in the background. (0.5 Mb image)

spotted lanternfly nymph head sensor

Spotted lanternfly nymph chemo-sensor 2

Zooming in on the chemical sensor, she found it covered with flower-like protrusions - probably evolved to have a high surface area to maximize contact with the air and so sense smaller amounts of airborn chemical.  I don't know why she didn't fix the name in the data bar to state "Grace Hetrick."  I think she just got too caught up in the discovery to pay attention to a little detail like that. (0.5 Mb image)

spotted lanternfly nymph head sensor close-up

Spotted lanternfly nymph chemo-sensor 3

The chemical sensor protrusions are amazingly consistent. (0.4 Mb image)

single spotted lanternfly nymph head sensor close-up

Spotted lanternfly nymph chemo-sensor 4

One final image of a single sensor on the organ projecting from the top of the lanternfly nymph's head.  The full image is about one eighth of a millimeter wide (one 200th of an inch) (1.4 Mb image)

backscatter electron image of molybdenum ore from China

Molybdenum ore from Henan, China

Michael Perrotta will probably cringe that I put this image on the internet.  I believe this might be one of his very first backscatter electron images.  The different shades of gray indicate different minerals that are composed of more (bright) or fewer (darker) heavy elements.  The white blades are molybdenite (MoS2) and the darker grays are skarn silicate minerals.  The sample is coated with a 15-nanometer thick layer of carbon to increase electrical conductivity.  The coating isn't perfect (not his fault!), so there are some bright charge build-up spots in the center with horizontal streaks (scan dislocation errors) that probably drive him nuts to see now that he's very adept at electron microscopy.  It was a learning sample!  Michael is one of those people who starts learning from scratch, like we all do, but really gets great at things by continuously improving. (8.1 Mb image)

tiny crystals on the surface of polished slag

Crystals on surface of slag

Marissa Loftus is a caver.  She goes underground in wild caves and maps both the patterns of the tunnels and the geology exposed in the walls.  I'm not talking about walk-in caves - these are the kind that require climbing underground cliffs with ropes, swimming through underground lakes, etc.  She collected a sample of slag from Lyon Mountain, New York.  Note that she's using a pretty strong beam (10 keV) because she was getting ready to analyze the chemical composition of crystals inside the slag using the EDS detector.  While getting her basic focus, though, she discovered this tuft of crystals that grew on the surface. (6.9 Mb image)

hopper crystal of halite (table salt) with triangular hole

Hopper crystals of salt 1

Dissolving a lot table salt (halite = NaCl) in hot water can result in very high concentrations of sodium and chloride ions.  When that supersaturated solution crystallizes quickly, the crystals can form hollow faces due to rapid crystal growth on crystal edges.  Hollow-sided crystals like this are called hopper crystals.  Halite and bismuth both commonly form hopper crystals.  Collin Green - an outstanding young entomologist (insect scientist) did a beautiful job with this image. (3.2 Mb image)

hopper crystal of halite (table salt) with square hole

Hopper crystals of salt 2

Michael Perrotta also imaged a hopper halite crystal sample, but at lower magnification.  The width of this image is almost 1 millimeter (thickness of a fingernail), which is like a mile by SEM standards. (0.8 Mb image)

hypodermic needle point with hole in middle

Hypodermic needle 1

Tyler Keefer is now a watershed resource technician, but I knew him as one of the most enthusiastic naturalists I've met at Kutztown University in a decade - wonderfully curious about the natural world!  He wanted to compare a hypodermic needle with the stinger of vespid (wasp).  He made a great mount on a single sample stub that made imaging the needle and stinger together easy.  This image was one of the first images we made with the SEM in the lab.  This is just the needle side, but illustrates nicely how the metallic needle is brighter than the carbon background, even in this secondary electron image.  This is because the steel also sends backscatter electrons to the secondary electron detector (not because the metal is shinier, because shininess is a property of light, not electrons).  Tyler did a great job with this, getting a very, very low magnification image that's entirely in focus by using a high beam energy and moderately long working distance.  Good job, Tyler!  (0.9 Mb image)

hypodermic needle point with surface texture

Hypodermic needle 2

Tyler then imaged just the needle tip at higher magnification (still low magnification, but zoomed in on the needle tip).  Here, he wanted to see the surface textures in greater detail, so he lowered the energy level of the beam and decreased the working distance.  Note how using a low-energy beam generates fewer backscatter electrons, so the needle and background carbon are similarly bright in the image.  Again, good job Tyler! (1.1 Mb image)

wasp stinger with barbed tip

Vespid (wasp) stinger

Tyler's vespid (wasp or hornet) stinger.  Note that the scale is ten times smaller than the hypodermic needle.  The horizontal lines are scan errors due to static electric charge buildup on this non-conductive sample pushing the beam one way or another as it sweeps back and forth across the sample.  Again, one of the very first images taken in the Kutztown SEM lab.  (1.1 Mb image)

blob of sodium molybdate chemical with microscopic crystals

Samantha Evans testing purity of reagents

Samantha Evans used sodium molybdate (Na2MoO4) in some of her experiments.  She was curious about the potential contamination of her reagents from the stock room, so she mounted samples straight from the bottles and analyzed them with the secondary and backscatter electron detectors, then with the EDS.  She did indeed find that her reagents were not perfectly pure.  You can see in this image little dark gray needle-shaped crystals that have  different composition from the main blobs.  (1.4 Mb image)

diatom shell with holes - low magnification

Diatom 1

Pam Edris was one a star marine science student who just graduated recently.  She has a great holistic/multidisciplinary view of studying ocean sciences.  She collected some diatoms on one of her sorties to the sea.
This is a medium-magnification image of one of her diatoms.  Note that she used a low energy (2 keV) beam because she wanted surface texture and because the sample is not coated, so she was avoiding charging on the surface, too. (0.5 Mb image)

Close-up of diatom shell with holes

Diatom surface 2

Pam then zoomed in to a higher magnification to be able to see the pores on the surface and sieves in the areolae (big holes) in the frustule (shell).  She did an excellent job with this.  There are a few tiny scan errors (horizontal streaks), but that's hard to avoid with uncoated, electrically non-conductive samples taking a 2k image across a 5.8 micron site.  (2.6 Mb image)

single human hair with scales

Human hair

I believe this is one of my own hairs.  Stephanie Shara - a biology student interested in neuroscience - cut samples from my head and from the heads of other students in the class to compare.  She and Pam Edris (marine scientist) did a nice job with this image - especially considering this was their first time using the SEM.  I'm no biologist, but I've long wondered how long each layer of scales on the hair take to form - is each a day of growth?  If so, does my hair grow when I sleep, but not during the day (or visa versa)?  I wonder how we could test these hypotheses. (8.7 Mb image)

blood vessel cave in a mouse brain sample

Blood vessel

Stephanie Shara also obtained a sample of mouse brains.  Her sample was interesting because it had been stained and plasticized, but had not yet been sliced with an ultramicrotome into a TEM sample.  We don't have an ultramicrotome, so we imaged the surface of the sample using the secondary electron detector.  Amazing to think that our bodies have tiny caves like this throughout all of our tissues!  (9.1 Mb image)