Sericulture, or silk farming, has been around for thousands of years. The humble silkworm moth, Bombyx mori, has contributed a lot to ancient civilization through this practice. It’s one of the oldest industries in the world and very likely one of the first luxury items, not to mention an amazing trade commodity back in the day. It’s smooth, very luxurious, but it’s also known for being quite strong: Mongolian and samurai armor is often held together with silk (but silk itself can’t block a sword; you can still cut it, after all). Oddly enough, and garment warnings will bring this up, water can weaken it. How? Without going into too much detail (we’re being casual here), it’s almost like silk is being dissolved. Just a little, not like it’s going to disintegrate with some light rain (setting up some of the most embarrassingly epic wardobe malfunctions) but just enough that it could warp. I wasted a beautiful blue silk tie once upon a time. Didn’t know better or read the garment care tag, probably because my first instinct was to rip those off, especially back in the day when they would sew that into t-shirts.
(a quick aside – whoever had the bright idea of tagless t-shirts should be given the Nobel Peace Prize)
I’m digressing. Anyway, as strong as natural silk is, there must be a way to make it stronger.In fact, there is: a team of researchers from MIT and Tufts University have just published an article on Nano Letters about a membrane they’ve made using silk from silkworm moths.Why do this, though? The authors want a new kind of filter compared to what’s out there: many of them are synthetic, which not only require a lot of different chemicals, some more hazardous than others, it can also start getting expensive. Also, some of the synthetic filters may have inconsistent pore sizes, which means it may filter out (or in) things that you may not want. Not cool if you’re using for, say, wastewater treatment. Finally, the big one – they wanted to make a filter that can stand up to being in water.
At this point, you’re probably thinking (especially with the last point) why make a silk filter if water can weaken it? What the authors propose, then, is instead of filters made from silk fibers, it will be made from fibrils; so think really thin fibers. How much thinner? A silk fiber is often 5-10 micrometers, which can be as much as 1/10th as thick as a human hair. Through a process that includes soaking it a special kind of alcohol, they can get fibers to separate into fibrils that can be as much 250x thinner instead of dissolving into molecules. In other words, through a process that’s relatively simple (in a lab, anyway), they can separate silk fiber like it was Twizzlers.
One would think that a really thin membrane like that would make a lousy filter. Instead, they got a filter that could be cut or bent without warping, and it doesn’t dissolve in water even when you put pressure behind it. Pore sizes are more consistent, which means that it’s better at separating only what they want, like proteins and dyes. In fact, they can even change the pore sizes with a few tweaks when making the silk membrane. All that, and water can still flow very quickly though it.
This is at least proof-of-concept, and clearly the next step would be a scale-up for industry. After all, really strong silk? Better filters for industrial uses like for wastewater treatment as the authors say, but what about clothing? Imagine silk anything that’s much easier to care for: you probably still wouldn’t throw it into the wash with your jeans (also, the inside of a washing machine is a violent place), but at least it’s got better survivability. If you’re really posh or a coffee/tea snob, picture this: silk-lined French presses. Patent it if you want, just do me a solid and plug my blog, will you? Weird (LEGAL) ideas are another service here at sci.casual.
Will it work, though? That’s what research is for.
Featured article: Ling S; Jin K; Kaplan DL; Buehler MJ. (2016) Ultrathin Free-Standing Bombyx mori Silk Nanofibril Membranes. Nano Lett. 16(6): 3795-3800. 10.1021/acs.nanolett.6b01195
Featured image photo credit: “Models in silk dresses at the MoMo Falana fashion show” Wikimedia Commons (CC BY 2.5 license, author: David Shankbone)