Imaging with Electrons

The use of the Scanning Electron Microscope (SEM) was initially one of the most exciting and nerve wrecking imaging-techniques I learned. However, after having to learn to work with three different generations of SEMs within a few weeks  (the oldest SEM being from what felt like the 1970s, whilst the newest had just been built and bought this year for the imaging department of the university), it turned into a peculiarly normal task.

I enjoyed the preparation of the samples in advance – desiccating them, before sputter coating them with a thin conductive surface layer of gold. This gold coat improves the SEM image for several reasons (not only because a shiny golden woodlouse if prettier to look at). For examples, it prevents charging effects (which can be seen as blobs or other noise on the image), it reduces thermal damage and it enhances the secondary electron signal of the SEM.

After placing the sample within the sample chamber, it be positioned either manually with levers or by order via the computer. The adjustment of the SEM settings and focus can also be done thanks to buttons on the machine or via the computer (depending on the SEM model).

Due to me working with rather large samples (mainly small crustaceans), each SEM-session yielded another image-puzzle. Thus, I stacked and pieced the individual photos together afterwards using Photoshop. You can see some of my favourite images below.

For those of you interested in more technical details and the physics behind the SEM, I recommend having a look here and here.

Water slater – Asellus aquaticus

Water flea – Daphnia pulex

Common Rough Woodlouse – Porcellio scaber


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