I have a confession to make. I don’t like bandages. They are:
- Never the right size so you have to use like 3 to not put the sticky part on the wound.
- Sometimes more painful to rip off than the actual injury because it sticks to all your hair and bodily fluids.
- Fall off when dusty or wet so when you go swimming there are a million floating on the surface.
- Leave gross residue so you look like the Hydroflask of a girl who decided stickers weren’t cool anymore.
- 1 in 4 people have a reaction to common wound adhesives so by trying to heal your wound you make it worse?!
And they’re literally the same as they were in 1921, 100 years ago.
It’s like we’re using the grandparents of grandparents for bandaids. Comparable to sending carrier pigeons for text messages.
So, I decided to change things. To make a much butter bandage. 🦋
Let’s Go On a Trip
Deep in the forest the wind whistles through the trees. Predators stalk about as strong gusts send twigs swirling through the air. But in this mayhem, a tiny pupa hangs from a sturdy leaf, unbothered.
This is the pupa of a greta oto (glasswing) butterfly. During its last days as a larva the caterpillar climbs onto the bottom of a leaf and begins the process of spinning and attaching a silk pad. This pad is composed of layers of randomly organized loops. (Many butterflies do this, but I’ll be focusing on glasswings).
Once the pad is complete, the larva will jiggle its cremaster — which is like a little stem of chitin at the butt of a caterpillar — into the pad. It takes a bit of moving & grooving for the caterpillar to feel comfortable enough to let go, but once it’s in, the attachment is at least 50 times stronger than needed to hold the chrysalis up.
The reason why the hook & loop closure is so strong lies partially in how the hooks are arrayed. Instead of a flat surface, they are put in a ball shape on the cremaster surface. Not only does this increase the surface area, but it also makes it easier for the hooks to attach without compressing the pad.
In addition to their arrangement, the hooks themselves have evolved to be great at gripping. The ends of the hooks have a backward facing barb meaning it’s easy for the silk to slip over, but not off. Then, at the end of each barb is two mini barbs with a groove for fibers to sit in.
This is unique because unlike a bur, which only has one hook per extrusion, the cremaster hooks have many more grooves and fingers for the silk to get caught in. This is why fishing hooks come with a barb on the end and why grappling hooks usually have at least 3 claws; it holds onto things better.
My Vision of Butterfly Bandages
This simple yet effective butterfly attachment process made me wonder if it could be used on bandages. To adhere to people, without any adhesive. My idea went like so:
Take some eco-friendly strips of fabric with good bandage potential, like Tencel, weave random (bioplastic or thread) loops on one side, put a mound of bioplastic hooks on one end of the other side, and then coat the whole thing in a film of chitosan and aloe vera.
Super easy, right? Yeahhh…
Why It’s a Good Idea
Obviously, the purpose of this article is to say that idea didn’t work. That being said, the idea was really great on paper solving all 5 of my biggest issues with bandages earlier.
Sizing wouldn’t be an issue because the strips could be cut to their desired length & width. As long as one end still had the hook mound, it would close.
The special closure solves the other 4 issues: pain on removal, adhesive wearing off, residue, and wound adhesive reactions. It would work similar to self-adherent wrap by staying on your skin via pressure (which is one of the things wounds need to heal anyways).
Chitosan has some amazing properties for wounds which is why the US Military already provides its soldiers with chitosan bandages. The layer of chitosan on the inside, non loop layer, helps to clot blood faster, reduce inflammation, and get rid of bacteria which could cause an infection.
Aloe vera has also long been used to promote collagen growth speeding up healing. It retains moisture (which reduces scarring), minimizes inflammation, is antibacterial, and has a cooling effect great for 1st or 2nd degree burns. Aloe vera bandages developed before greatly decreased the time it takes for wounds to heal compared to using a standard bandage.
Except It Doesn’t Actually Work
As hard as it is for me to admit this and discontinue >1 month of research, the bandage really does suck. Yes, today’s bandages have problems, but mine just bring their own set of them.
All that jiggling caterpillars do to attach their cremaster to the pad? It’s a lot of work. Nobody wants to spend even just 10 seconds wiggling their bandage around when they could just slap on a non butterfly bandage in a fraction of the time.
The only area butterfly bandages might have an advantage would be on larger wounds such as to the thigh or abdomen because these just require more care to begin with.
But before we can even get to using the bandage, how would it be manufactured? The closure is similar to Velcro, so one might be able to modify a machine like this one. But, that’s a bit lame and even if I could weave in loops they wouldn’t be as effective as original glasswing ones because of their ordered nature. By getting rid of the random weave of the silk pad, the closure no longer has as much isotropic strength (the same in all directions), decreasing flexibility.
And then we have the hooks. Making them as detailed as they are with all the barbs is hard. Especially since they’re teeny tiny and on a 3D object. BUT, biomimicry doesn’t mean blindly copying nature. You’re totally free to simplify things if it makes more sense for your specific scenario. Except, if we were to simplify this, we would literally get Velcro!!!
The chitosan and aloe vera contribute a lot towards the effectiveness of the bandage, yet I’m not sure how I would be able to incorporate both at the same time. My best idea would just be a film of chitosan and microcapsules of aloe vera that release when the bandage touches skin. Unfortunately there’s not much information on how microencapsulation affects the properties of aloe. Dry aloe doesn’t have the same effectiveness but just soaking the bandage in gel would be very…slimy.
I wanted my bandage to be an environmentally friendly option to replace plastic & cotton bandages. Well, turns out it’s probably a lot worse for the earth than conventional choices. All this specialized machinery and all the extra materials required will likely far outweigh the carbon footprint of just a quick plastic bandage.
Not to mention that they’re dirt cheap compared to what I’m proposing. 😳
Lessons Learned & Conclusion
When you’re so excited at the beginning of a project and then later when you’re in the weeds, it’s easy to forget the end goal. For me, I got so excited about chitosan and aloe vera that I forgot the most important part: the biomimetic closure.
Instead of “tackling the monkey first,” I started with the easy & less important stuff (what fabric I want, how to make a chitosan coating, etc.) all the while telling myself that after I finish reading this article about the underwear company that puts aloe vera into their fabric I’ll get to the important stuff. I even went so far as to buy a (pretty expensive) bag of chitosan off of Walmart — all before knowing how I would get the bandage produced.
It also didn’t help that I added so many frivolous things to my bandage’s design that I struggled to explain it when people asked what I was doing.
The way butterflies attach themselves to leaves when pupating is really fascinating to me still, but maybe it was too enticing. Instead of doing lots of research on how nature attaches to things without adhesive, I just chose the glasswing after a couple of Google searches.
Failure is uncomfortable. I was in denial about it for a while. Couldn’t rip the bandaid off ;) But once you learn to push past that initial frustration you can begin to embrace it. So fail, learn, keep at it, and move on.
To summarize, to avoid this in the future I will figure out the hardest part of the solution 1st, keep it as simple as possible while still being effective, and make sure I’m only attached to the problem, not solution.
I’ve yet to see a biomimetic bandage, but in the meantime, I’ll just have to settle for my Avo-Cato bandages.
Hey! I’m Klara, a 14-year-old extremely passionate about biomimicry. I love working on projects and documenting my work with articles and videos! If you enjoyed this article, please give it some claps and follow me on Medium. ✌
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If you’re interested in glasswings, chitosan, or aloe vera check out these 3 papers below which helped me SO much:
Structure, mechanism and mechanical properties of pupal attachment in Greta oto (Lepidoptera…
Abigail L. INGRAM , Andrew R. PARKER , Department of Zoology, University of Oxford, South Parks Road, Oxford, UK Search…
4.1. Extraction of Chitin The primary commercial sources of chitin are crab and shrimp shells. The isolation of chitin…