Gallery of secondary electron images by students

table salt crystal with hopper surface hole

Table salt hopper crystal (3.2 Mb image)

Student gallery of secondary electron imagery

The university website only allows me to show 740 pixel resolution images because they prioritize fast downloads and people viewing on their phones with slow download rates.

The Gemini 300 electron microscope, however, can take images with resolutions of up to 32,768 x 24,576 pixel (an 800 megapixel image!!).  Taking images of that ultra-high resolution take a very long time (hours), which can cause static charge build-up.  We've found that 6,144 x 4,608 pixel images (28 megapixel) are plenty for most applications, and most users just take 4,096 x 3,072 pixel images (12 megapixels) because the image quality records excellent detail and takes only 2¾ minutes to capture the image.  Some even take very quick 2048 x 1536 pixel (3 megapixel) snapshots because they're in some kind of hurry.

This is a gallery of thumbnail images with links to full-resolution secondary electron images in the captions.  Please remember: most of these are images taken by undergraduate college students and high school students, in most cases with only first-time introduction to the SEM (e.g., within 30 minutes of fist time in the seat) - not images taken by professionals with lots of refined 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.  Most students who continue working with me or who take my Practical Scanning Electron Microscopy course develop very excellent microscopy skills (and then they are then forever disappointed with most of the imagery they see in professional scientific publications and on the internet  ).  Note: these are also just the jpg versions of the images - the tif images retain even more detail!

Norwegian spruce pollen

Norwegian spruce pollen

The campus is surrounded a row of Norwegian spruce which pollenate heavily in the spring.  It's amazing to watch, but also annoying to people with pollen allergies. The image is pretty dark because it is uncoated and also probably because I the lab monitors set too bright.  (6.7 Mb image)

single Norwegian spruce pollen grain

Norwegian spruce pollen

The pollen disperses in the wind (as opposed to being transported by an insect, etc.).  For this reason, the pollen has two "wings" called sacci to help carry it on the wind.  (1.7 Mb image)

surface of single Norwegian spruce pollen grain

Norwegian spruce pollen

The surface of the body ("corpus") has a knobby texture - maybe to help it catch the wind, too?  (1.9 Mb image)

Painting of an asteroid impact vaporizing rock (by artist Claus Lunau)

End-Cretaceous impact spherules

At the end of the Cretaceous Period (66 million years ago),  an asteroid collided with Earth near Mexico's Yucatan Peninsula.  The rock had tremendous kinetic energy because it was big (5 km = 3 miles wide!) and moving fast (estimated 20 km/s =  45,000 mph!).  When the rock hit, kinetic energy turned into heat energy, vaporizing rock into a gas that spread across much of the Earth.  As the gas cooled, it condensed like morning dew, first forming liquid rock (magma), then quenching into tiny glass spheres called spherules that rained down over thousands of square kilometers (or miles).
(amazing drawing by Claus Lunau in National Geographic)

spherule of condensed rock vapor formed by the asteroid impact that killed off the dinosaurs

K-Pg (K-T) spherule
from dino-killing impact!

Dakota Pittinger – nicknamed “Paleo McConaughey” because he has an encyclopedic knowledge of dinosaurs/paleontology and he looks like Matthew McConaughey – obtained a sample of spherules from the K-Pg boundary.  The spherules in this sample rained down on the seafloor (a quiet environment that’s great for preserving them).  The seawater reacted chemically with the glass, though, forming tiny crystals of clay that make these surfaces rough. .
(amazing drawing by Claus Lunau)

spherule of condensed rock vapor formed by the asteroid impact that killed off the dinosaurs

K-Pg (K-T) spherule
from dino-killing impact!

Individual spherules appear to have an inner core and outer shell.  I suspect the outer shell is the depth to which seawater altered glass to clays at the time of deposition, and the core was still glass.  That boundary would have been the limit of chemical reaction.
(8.2 Mb image)

spherule of condensed rock vapor formed by the asteroid impact that killed off the dinosaurs

K-Pg (K-T) spherule
from dino-killing impact!

The cores pop out, leaving the platy clay shell.  You can see the plates of the clay minerals on that inner surface, too.  The smooth surface on the top left of the shell is where we accidentally smashed the sample when mounting it onto the sample stub.  Isn’t it amazing to think that 1) rock can vaporize into gas, and 2) rock vapor condenses like dew into glass beads that rain down onto the Earth?  It’s an amazing world!
(9.4 Mb image)

Map of western U.S. showing where ancient lake deposits and diatomaceous earth deposits are located (image from USGS)

Distribution of diatomaceous earth deposits in the western US from USGS Fact Sheet 2006-3044

The Miocene/Pliocene sedimentary rocks are old lake beds (23-3 million years ago - when the western U.S. was wetter, before the recent Ice Age.

Diatomaceous Earth

Diatomaceous earth is a remarkable material.  EP Minerals (a subsidiary of U.S. Silica) digs up old lake beds in Nevada for use in water filtration, chemical-free pesticides, and anti-clumping agent in powders (including medicine!)  It is valuable because it is made of gazillions of microscopic shells of photosynthetic plankton - shells made of the mineral quartz (SiO2).  During the Miocene and Pliocene geologic epochs, these creatures thrived in giant lakes, then their shells sank to accumulate on the lake bottom when they died.  Year after year after thousands of years, the shells accumulated into thick layers of soft rock.

diesel shovel loading a mining truck with diatomaceous earth in a mine in Nevada (image from EP Minerals)
whole diatom in diatomaceous earth from Nevada

Whole Aulacoseira sp. frustule

Whole diatom - roughly 30 μm long (roughly one thousandth of an inch) surrounded by debris of broken other frustules.  The broken frustules are like microscopic broken glass, which gives diatomaceous earth its pesticide properties – harmless to giant humans, but tough on insects. (9 Mb image

join (girdle band) of a diatom shell (frustule)

Girdle band of diatom

These frustules connected with one another with an interlocking join (see middle of whole frustule image).  At this magnification, you can start to see the microporous texture of the surface of the frustule, too, which helps give diatomaceous earth it's absorbent characteristics. (9 Mb image

pores (areolae) in a diatom shell (frustule)

Diatom pores (areolae)

Having a body of transluscent quartz is great for protection and letting light in for photosynthesis, but quartz is waterproof and gasproof, so the diatom needs a way to let CO2 into the frustule and let O2 gas out.  The pores (areolae) have a fine mesh of quartz that prevented even the tiniest of predators from getting into the cell.  Is it any wonder that we use diatomaceous earth for filtering contaminants to make safe, clean drinking water? (9.4 Mb image)

ant head magnified showing jaws, eye, and antennae

Front end

Low magnification "yearbook portrait" of the ant that give its life for this exploration.  (17 Mb image)

Acidopore? ("butt") of ant

Back end (acidopore?)

Everyone's got one.  This is this particular ant's rear end.  Some ants have stingers, others have acidopores (from which it can spray formic acid).  The claw at the top of the image is one of its six feet. (17.5 Mb image)

Ant from my kitchen countertop

My kids have a running joke that whenever a bug gets in the house, or we find a weird piece of metal or dead animal body part or ... almost anything that might be interesting to explore microscopically, they look over at their dad and ask if it's going into the SEM.  Since they're right more than half the time, I can't argue.  This sample was an an I found crawling on our kitchen counter. (16.9 Mb image)

Ant eye with many facets


This image of the eye of the ant shows one of our early attempts with the metal sputter coater - a tool we use for depositing an ultrathin layer of gold on the surface. (Please click here to learn more.)  The gold makes the surface electrically conductive and also emits more electrons when hit by the electron beam (giving us a brighter signal).  The dark lines between the facets of the eye are where gold did not deposit well. (7.4 Mb image)

Ant jaws (mandibles)


This is a low magnification image of the jaws (mandibles) with an antenna coming out of the "nose hole."   I'm always fascinated by imagery of creatures at this scale because I imagine this being the norm for each species.  We might find this monstrous if we ran into something that looks like this alone on a dark night, but for other individuals of its species, this might be a reassuring face of familiarity and aesthetically-pleasing features.  I suppose we all anthropomorphize sometimes. (20.1 Mb image)

close-up of ant jaws showing chipped "teeth"

Jaws detail

This is still just a medium-magnification image, but life's not always about doing the most extreme thing - it's about doing the thing that's right for the moment.  This is the scale that best shows the feature of interest: the wear that the ant has experienced on its jaws (mandibles) when it's chomped on hard things and "chipped a tooth." (18.4 Mb image)

tip of antenna of ant

Ant antenna - low mag

The tip of one of an ant's antennae looks so much gentler than the sharp claws on its "feet." (7.2 Mb image)

close-up of antenna of ant

Ant antenna - medium mag

Zooming in on the joint between segments of the antenna, we can see how the hairs attach, and that there are some tiny holes (maybe spiracles for getting oxygen into the exoskeleton?)  If you look at the high resolution image, you'll be able to spot a little dark gray rectangle near the center where we looked at the surface at high magnification for too long, leaving a little "burn mark." (9.4 Mb image)

close-up of hairs on antenna of ant

Ant antenna - high mag

We can still comfortably zoom in 10 times closer than this, but this scale shows the wavy texture of the surfaces of the shell (exoskelleton) surface and hairs (setae) nicely.  The width of this whole image is about 25 micrometers = one thousandth of an inch (7.2 Mb image)

Puffball fungus spores

Puffball fungus spores

These images are very dark and it's totally my fault.  I just patted some sticky tape on the fungus surface so spore stuck, blew off the loose excess spores, and put the sample in the SEM.  There is no gold coating, so nothing to brighten the secondary electron signal.  I used a very gentle beam with a much-too-short working distance for the detector (when the sample is too close the electrons can't get to the detector well due to shadowing). I did almost everything wrong - learning is a process. (1.5 Mb image)

Puffball fungus spores

Puffball fungus spores

My very poor sample preparation and bad sample positioning made these images too dark.  Brightness and contrast can be adjusted in post-production - these are raw - but the point here is to showcase how even poor prep can produce informative imagery.  The Gemini 300 SEM is not 100% fool-proof, but I haven't met a fool yet who couldn't get useful imagers with it. (1.2 Mb image)

Puffball fungus spores

Puffball fungus spores

The surfaces of each spore are rough.  I suspect that is to better help them be carried by the wind.  Each spore has a single stick, which might be the original structure from which they grew on the sporangium (?), or maybe they are germinating and those are the first hyphae as the spores start their new lives.  As the sign in the lab says, "Dr. Friehauf is not a biologist." (1.1 Mb image)