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UV Fluorescent Silkworm Cocoons – Mini-Project 4
Mini-Project 4
Topic: Exploring the ultraviolet fluorescence and colouration of silkworm cocoons Duration: 6 weeks Outputs: Paper-style report, lab book & poster presentation
Hi guys!
The topic I’ll be talking about in this post is my fourth and final 6-week project of Year 3. I was allowed to choose absolutely any project from any supervisor in the Materials Department, so I chose to do something very different to my previous projects and work with these little creatures:
Image source: Natural Materials Group, University of Sheffield, UK
Now, I wasn’t just trying to befriend them by the way. The Bombyx mori (B. mori) silkworm has been domestically bred for thousands of years owing to the lustre, strength and durability of its fibrous protein secretions, known as silk. Silk has also been historically used as a suture material, but in recent years it has also found popularity as a biomaterial. However, in addition to exhibiting remarkable mechanical and biocompatibility properties, it turns out that the cocoons spun by certain breeds of the B. mori silkworm fluoresce under ultraviolet (UV) light! Furthermore, the cocoons may fluoresce different colours based upon their sex: yellow-white if spun by a female, or blue-purple if spun by a male (as shown in the bottom left and right images respectively in the figure below). Note that you can't tell what the sex of cocoon is under visible light (top 2 images). Cool, eh?
Images source: Natural Materials Group, University of Sheffield, UK
Interestingly, there are also differences in the quality and mechanical properties between silk spun by males and females, in that male cocoon silk has a smaller cross-section and is of 1-2 grades higher than that of female cocoons; cocoons of a higher grade are generally whiter in colour (less discoloured), easier to unravel, larger in size and tend to be stronger. Yellow fluorescent cocoons spun by males have a greater reelability than their purple counterparts, rendering male cocoons more desirable for the silk industry. Tough luck, ladies!
Since the colouration affects the quality of the silk for producers and the biomaterials industry, the phenomenon of fluorescence in the cocoons is pretty intriguing. So here is the research question which I was trying to tackle for 6 weeks: how does the humidity level during spinning affect the fluorescence and colouration of cocoons?
To begin with, I needed to image the cocoons under both UV light and visible light. In order to do this, I custom made the UV disco box below – or multi-wavelength illumination module, to be exact.
Image obtained from project work undertaken as part of the Natural Materials Group, University of Sheffield, UK
The activity in this project involved handling the silkworms and setting them to spin in different environments; popping them out of their cocoons (still alive, of course); doing a lot of microscopy and Fourier transform infrared (FTIR) spectroscopy – to gain an idea of the chemicals in the silk.
This is what most of the discs cut from cocoons looked like under UV light and visible light:
Images obtained from project work undertaken as part of the Natural Materials Group, University of Sheffield, UK
However, one cocoon was extremely bright compared to the others; the picture below shows what a disc cut from the cocoon looked like under UV light! Compared to the UV images in the figure above, it's clearly pretty different...
Image obtained from project work undertaken as part of the Natural Materials Group, University of Sheffield, UK
I’d say that this project has been the most full-on in terms of workload but I don’t know if that’s partly my own doing because I was so eager about the whole project! My supervisor was absolutely brilliant and, in my opinion, it really did make all the difference. Incidentally, the poster I created for the poster presentation ended up being black with some text in yellow – I thought this was a bit risky compared to the usual pastel colours found on posters, but my wacky, lovely supervisor loved it. Getting on with the whole group working in the lab was an added bonus; I was even sad to leave them. Having the opportunity to work with natural materials has been fantastic and it wouldn’t have been possible without the MRes course at Sheffield. I certainly wouldn’t have been able to test the waters of so many fields.
So here’s what I have learnt from Mini-Project 4:
Try something new. Change things up a bit with different topics if you have the leeway; choosing the same sorts of areas might become monotonous, even if you think you have a head start in terms of prior knowledge. It sounds obvious, but pick a topic you think is exciting!
If you have the privilege of choice, then choose your supervisor carefully! Meeting them before committing to a project not only allows you to gauge if you work well together, but it will also let them know that you are keen and proactive; they may well even choose you over another student if you make the extra effort and you’re not just a name on a piece of paper.
Having a good relationship with others in the lab will benefit both parties. You can help each other, discuss ideas and have a pleasant day in the lab. People can sometimes point out things which you may have overlooked or vice versa.
Keep your poster as concise as possible and ensure that it is visually appealing. Use lots of interesting photos. (People were pretty intrigued by the worm and UV disco box.) Your poster is an advert for your work. If the poster looks good, people will be drawn to it and you will have the opportunity to interest and inspire them.
Ask your supervisor to go through your report or poster with you. My supervisor told me that there often isn't much point in them in giving you advice on your work after you've finished the project as you'll never look at it again!
Top tip: Consider both the project topic and supervisor carefully. Don’t be afraid to try something new if you have the leeway to in your degree – now’s your chance.
Hope you enjoyed reading about my favourite project so far! I never thought I’d be working with creepy crawlies in a million years.
Leave me a comment or question below, and good luck in your future projects ☆
