Using the simple sharpie dark-field setup to visualize C. elegans


I was lucky enough to get my hands on some Foldscopes for a STEM outreach activity. The goal with the Foldscopes was to view C. elegans using as simple of a setup as possible so that all of my students could try something similar at home.

For my light source, I followed the suggestions in this post:

Throwie LED as Foldscope light source 

but found that regular masking tape worked just fine instead of conductive copper tape.

I was inspired by this post (below) about the dark field setup for C. elegans using  because they are transparent and hard to visualise.

Simple dark-field : improve your imaging contrast with another classic microscopy technique

I decided to give things a go for myself using the dark-field Sharpie method. Unlike some suggestions, I found that the “dotting” method didn’t work for me as well as the “line” method on a glass slide.

Here’s a picture of the back of my Foldscope. I have two watch batteries taped down simply so it sits evenly.


I then pipetted roughly 20 uL of a solution containing C. elegans in M9 buffer onto a glass slide. On either end of the glass slide, I have some cardboard to create space so the C. elegans don’t get squished, and then used another glass slide and some masking tape to sandwich everything together like so:


In the end I was able to get the following video:


Reading some posts, I was very impressed to see what others have done on “the dark side” with paper apetures, etc (see below) but it was still great to see what I could get away with using a good old Sharpie.


C. elegans in bright field and dark field


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