Manipulating a diatom inside a Foldscope 

Yesterday; with the help of Paul, we went out in Monetrey Bay and did a plankton tow to pull out all kinds of things from the ocean. This was a 100micron screen; so we got a lot and lot of stuff. I have an infinite amount of microscopy to do – but I wanted to share a quick idea – I figured out that I could manipulate a single diatom by just playing around with the foldscope focus. 


Here is a cyclotella; watch it rotate in the field of view. It’s going to divide soon – and hence you see the two frustals that will desperate out. 

By applying pressure on the slide; I was able to generate a very gentle flow that flips the diatom around – and i get to see the diatom in its full glory. 

If you look carefully; you will actually see some very subtle features including an exclusion zone of the outside plates, radial fibers and more. 

Now; I have maybe 20 or so different species of diatoms I imaged. Inspired by work from @Laks; I will also organize that in a database. 


4 Comments Add yours

  1. laksiyer says:

    Dear @Manu. I like the manipulation. Did you use a glass coverslip or cellophane tape? A database of diatoms sounds wonderful. I hope you can catch it dividing, one of them will be smaller than the other… this continues for a few divisions and there is a recursive dimunition of one descendant. I have only read a lot about it, but havent seen it.

  2. Manu Prakash says:

    @Laks: yes; I used a glass cover slip with tape as side holders to make a spacer. I take one sided tape and fold it to give thickness of two. I put the cover slip supported by the two side tape – and finally add another layer on tape to make the cover slip not move. So I have a fluid trapped under the cover slip. Now – when I push to focus in and out; I am gently pushing on the top of the cover slips – that invariably creates flow. Most of the time they are a problem (the way to eliminate them is to use rigid side wall supports and seal the cover slip with nail polish); but when you a flexible support – that leads to a very nice control of flow. Cyclotella rotate beautifully in this flow. What I love about this movie is I am able to do a manipulation very repeatedly – and hence really control the same.

    Now, on size – I did run a time lapse on this guy to see when it divides – but my phone ran out of battery out doors. I will run it again. But I did find many cyclotella in this batch with variation in size; showing that they get smaller and smaller.

    Now the question is – how do they determine what is small enough and now they need to switch the mechanism of division to restore size. It’s a beautiful problem of size control 🙂

    Will try to start a small database for diatoms for people to start populating.

    @Tom: can you look at a wordpress plugin that allows community editable databases. It would be nice for people to populate general databases; that we can have curators maintain and do corrections on.


  3. Manu Prakash says:

    @Laks: I got some really Incredibl goodies from the ocean. Will pin you when I upload my latest datasets 🙂 you will really like them.

  4. Cristina says:

    Wow! It amazes me how neatly you have imaged the outside structure of this “drum like diatom” with only 140x. The way you manipulate its position/movement is fantastic. I really love reading your posts. Nature blossoms so differently through your eyes. Always focusing in new challenges that, as a biologist, I had seldom thought about before. This is science 100 %. Thanks.

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