Electron Microscope Mystery 1Posted: March 1, 2012
Before I became a federal funder, I ran a beautiful environmental scanning electron microscope (E-SEM). Unlike the binocular microscope you probably peered into as a student, an SEM uses electrons, not light, to produce an image. Because electrons are so tiny, you can see things at a much higher magnification than you can with light.
Other reasons electron microscopes are cool include 1) things closer to the beam appear lighter, and things further, darker (as though they’re in ‘shadow’) giving the appearance of 3-dimensionality, and 2) materials made of heavier elements have a higher contrast (and appear brighter) than materials made of lighter elements (which appear darker). For example, if you looked at an object made of aluminum (Al) and lead (Pb) stripes, the Pb lines would be brighter than the Al stripes.
For decades, electron microscopy required that samples be very small, polished flat, and coated in something conductive, like gold or carbon. An ‘environmental’ SEM, however, has a huge chamber, within which you can put a range of materials of varying shapes:
When I met my first E-SEM over 4 years ago, I needed to see what materials and shapes fit in the chamber, and which responded well enough to the beam to get good images. So like any good scientist, I experimented. These experiments resulted in a collection of electron microscope images of everyday objects, and I quickly realized the joy that comes with making friends guess what the objects were, based on high-magnification electron images. I ran this series on Flickr for a while, years back, but thought I would resume the fun here.
Thus, I give you #1 in the Electron Microscope Mystery series. The image below is about 70 microns across (0.007 cm). Can anyone guess what this is? I’ll update later in the day with a wider field of view.
Update at 1:20p: Added two views, each zoomed out a bit more (the width of the last is about 0.7mm wide…
Update at 2:40p: It’s been solved! These are ink particles pressed into paper fibers. The sort of pointed shape you see is the point of an upside-down letter M: