Watching individual bacteria swim under a Foldscope

In our lives; all of us have heard of bacteria. It’s a word so commonly tossed around; all the way from “microbiome” news craze where bacteria control many aspects of our lives (and they do) to yogurt to washing our hands and brushing our teeth. We tell little kids – if you don’t wash your hands, you will get infected by unwanted bacteria.. 

But how many of us have seen a live bacteria ourselves. That’s where Foldscope comes in.. The value of pairing “experience” with “knowledge” allowing concepts that we just read about to become physical and real in our mindset. 

Here is a tutorial to watch single bacteria swim via your Foldscope. This is an advance tutorial – and you should first replicate this post for focus locking and field of view locking before moving to imaging bacteria. 

Focuslocking, field of view locking and using ambient light (table lamp) as illumination 

Once you have gotten a focus locking and field of view locking working – and have a table lamp setup as a light source; it’s time to try watching bacteria swim. For this post; you must use a glass slide and thin cover slips since bacteria are small and you need the best resolution images. 

Now you want to find a sample which has bacteria. Which would be almost about anything. But having bacteria in high enough density is a good place to start. Now we can get some inspiration from Leeuwenhoek (who discovered bacteria with a single lens microscope). His famous discovery of bacteria came initially from leaving “pepper” soaked in water for 3 weeks. You could essentially take any food item in your kitchen; leave it in a small bowl for a couple of weeks (it will start to smell – a great sign for bacteria in high density). I usually collect water from rotting flowers; but that’s another story. 

I use “number 1” cover slips that refer to the thickness of the cover slip. Take a drop of water and put cover slip and tape sides. No need to seal it if the drop is small enough. 

If you have perfected your pseudo-phase and dark field technique with a table lamp – you should see a million bacteria swimming around. The little dots you see in this video are alive and actively swimming in water. Each of them range from 1 to 10 micron; roughly 100 times smaller a than width of a human hair. 

Another view of darkfield setup with swimming bacteria – with 150x Foldscope. 

Now, if you have perfected your focus locking technique; you can start using the 450X lens provided in Kit. I have to state, you should first get good at using a Foldscope. The high mag lens has a small back focal length; and thus focus locking is crucial to get good images. But once you have mounted your high mag lens correctly and have focus locking working – this is what you might see. 

Here, I see long and elongated objects happily swimming in the fluid. An almost erratic dance is mesmerizing. Sine most bacteria are usually rod like – to spectate them would require “sequencing” techniques. Several stains can be used to differentiate broad categories of the bacteria. But what I enjoy most is love microscopy; and it’s a thrill to see them swim around. 

Below, I also share videos of what the same video looks like with the illumination module provided with the kit. The contrast is higher for the “table lamp” illumination – but bacteria are clearly visible. 

So next time you have to convince a 4 year old to wash hands before eating; pull out your Foldscope and “show” them bacteria – don’t just talk about them, see them. 



Note: Post a comment once you replicate this. Would be wonderful to see many kinds of bacteria. 

Note: please wash hands after working with a live bacteria culture. Who knows what growing in your kitchen. 

15 Comments Add yours

  1. roshan says:

    hello sir can you tell me the slide preparation to see the movement of the organism under foldscope.

    1. Manu Prakash says:

      This is just a regular slide with a cover slip. The only specific thing is choosing a sample that I knew had a lot of bacteria (since I could smell something funny). I am using dark field and angular illumination (see the post) to get the contrast seen in these videos. Best place is to practice with slightly larger objects with this kind of contrast first. Make a post and share your challenges and I can help.


  2. monir says:

    Hi Manu,

    Thanks a lot for the tutorial!

    I have recently ordered a foldscope and waiting for it to arrive. I am a microbial ecologist, and it would be wonderful if I could inspect samples for bacteria or other micrometer sized organisms. Unfortunately, the current foldscope only has two 140X lenses. Can we expect higher magnification lenses anytime soon? Please let me know!

    Thanks again and best wishes!

  3. Rupjyoti says:

    Dear Manu Sir,
    I previously mailed to DBT and foldscope team relating to a problem we have stumbled upon in implementing our project. We are trying to visualize spores of Nosema sp. which infects silkmoths and creates havoc in sericulture. Nosema is also a menace in apiculture which leads to colony collapse disorder. Typically, a simple microscopic technique is utilized to observe the spores under (min 400X to 600x – depending upon the spore size of Nosema 2-20 μm) field and observe for greenish spore structures with Brownian movements). For this we ordered basic classroom kit in bulk because our objective was to train sericulture farmers who cannot afford to buy conventional microscope and other issues like lack of electricity and see its acceptance by the farmers. This has huge applicability for making disease free silkworm seed production in the country which is significantly affected by Nosema spores and make foldscope a widespred utility in sericulture sector. But we failed owing to the limitation of 140X mag. Coming across this post, I can see live bacterial motility is beautifully visualized. Do I need to switch to a Deluxe kit (as it says it comes with 2 * 140X lenses) ? Will it work ? Please guide me in this matter.

  4. Manu Prakash says:

    Dear @RupJyoti,

    All this data is collected with a regular 140x foldscope – the application you describe should be very doable. I can also link imaging of 2um particles to calculate diffusion coffecient – that tutorial is also on the site.

    Why don’t you create a post describing the exact challenge – and many in the community will help you implement the proposal by clearing describing techniques and link relevant tutorials – but it’s useful if we do this discussion on your post. This way you can provide the background for how important this problem currently is.


  5. Rupjyoti says:

    Dear Manu Sir,
    After the 2nd video of Bacteria in darkfield under foldscope 150x you have given another video using 450x magnification lens provided in the kit. We have ordered both Individual and large classroom foldscope kit but didn’t received any lens of 450x Magnification. Can you please help sir, where can i find it?

    Rupjyoti Das

    1. Manu Prakash says:

      Dear Rupjyoti, the current foldscope kit only comes with 140x lens. All the instructions for making 450x Lens are in the original plos one paper. Depending on what you are trying to do; I can suggest options.


  6. This is awesome…. Will update my videos soon 😉 been busy for a while :'(


  7. Rupjyoti says:

    Dear Manu Sir
    As per your suggested link
    I couldnt find same place on foldscope as shown in the above link since the models are different so i put the paper wedge below the lenstage and focus ramp but above panning guide and sample stage such that the light source is unblocked and tried viewing the pebrine spores (2- 20μm size) but the images are not clear . what should i do to fix the problem sir?

  8. Rupjyoti says:

    Dear Manu Sir
    As per your suggested link
    I couldnt find same place on foldscope as shown in the above link since the models are different so i put the paper wedge below the lenstage and focus ramp but above panning guide and sample stage such that the light source is unblocked and tried viewing the pebrine spores (2- 20μm size) but the images are not clear . what should i do to fix the problem sir?

    Rupjyoti Das

    1. Manu Prakash says:

      The idea works on all the models. You need to use dark field mode by using table lamp as light source. Here is a 12mon video tutorial of the same oblique illumination – but with the new model.

      Watch the whole video step by step and repeat.


  9. aliosmankoca says:

    hi, thank you so much.
    can I ask you and Manu a question, you wrote 450x above. Fakat foldscope 140 x . is this a digital zoom or a different method?

  10. says:

    Hi Manu, I was interested in checking if a Foldscope can be used for checking on microbial life in soil and to use it in carrying out soil health assessments. I have a foldscope with the 140x lens, and from what little I’ve read I understand I would need a 400x lens for a better analysis of soil life. Can I buy an old foldscope with the 450x lens ? I am based out of Delhi and it would be great if you can connect me to any foldscope users in Delhi. Thanks

  11. Tyro says:

    I tried lot of samples (tap water, saliva, animal pee, etc) but I never see any bacteria, my foldscope is working well I only saw onion cells once and no bacteria!!

  12. Manu Prakash says:

    @Tyro: Try starting with something that stinks.. literally. High density bacterial growth generates many volatile compounds and it is a good tell tale sign for the same. Any swamp/puddle/pond where you can see coloration in the water; or places where things have rotten and you can smell the same – is a great place to start.

    Also; if you are good with your foldscope – it is also very easy to image bacteria in your own mouth. You can follow another one of my tutorials here:


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