What can spiders teach us? Aside from abject
fear. Hi spider men and women, Julian here for DNews.
There’s a widely circulated factoid that claims spider silk is 5 times stronger than
steel, which is true, in a way. There are a lot of different spider silks and a lot
of different grades of steels. Some of the strongest silk can withstand over 1 GPa of
tugging before it snaps. By comparison a steel wire the same thickness can have a tensile
strength almost twice as high, but when you consider that spider silk is much lighter
than steel, then, yes, it can have about 5 times the tensile strength of steel by density.
Not as pithy as the factoid, but more accurate. The area where spider silk really beats steel
is toughness. Spider silk is extremely ductile, meaning it can really stretch out. That, combined
with the amount of force needed to break it when it won’t stretch anymore means it can
absorb 3x as much energy as kevlar before breaking, which explains why Cap couldn’t
get his hands free. Obviously if we could replicate spider silk synthetically it could
have a lot of applications, but we’re still untangling its secrets. (See what I did there?) There have been a few mechanisms that scientists
believe contribute to the silk’s ductility. In 2012 Dr Markus Buehler of MIT reported
to the journal Nature that he had found four stages the silk underwent as it stretched.
First the thread is pulled tight, then the proteins themselves start to unfold, the thread
then stiffens, and finally when it starts breaking, it does so a little bit at a time.
When the hydrogen bonds holding the proteins together break, some of them immediately reform.
It does this repeatedly, with fewer bonds coming back together each time, until they
can’t reform anymore and the thread snaps. The protein stretching and hydrogen bond failsafes
are hard to replicate in a cost effective way. Multiple attempts have failed, including
one that used genetically modified goats that made a protein in their milk that could be
spun into spider silk. But scientists have recently made a discovery about spider silk
that makes it’s stretchiness more replicable with the materials we already have. Scientists at the University of Oxford and
the Université Pierre et Marie Curie noticed that the orb spider’s silk is always taught.
Bend it, shape it anyway you want it, as long as you tug it, it’s alright. Not only that,
but when it’s compressed it still stays taught. On closer examination they found thousands
of watery glue droplets along the strand, each a tenth of a millimeter across. The glue
is useful for trapping prey, but on top of that it helps give the thread its elasticity.
When the the filament shortened, these droplets would reel in the slack. When pulled on, they
would spool it out again. The silk could be elongated and shortened as many times as the
researchers liked and it would still behave just the same. With that model in mind, the scientists placed
a droplet of oil on a plastic filament and viola, they made themselves a “liquid wire.”
It stretched out like a solid, but contracted like a liquid, making it a hybrid material.
Though the droplet was much bigger than the spider’s glue and the plastic was much simpler,
they still managed to mimic some spider silk properties, and they didn’t have to use
a single spider goat to do it. The researchers are optimistic their discovery can be used
when microfabricating complex structures, reversible micromotors, or other tiny systems
that need to be able to stretch and retract themselves. If you want more DNews, you’re not alone.
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Click the link in the description below to subscribe!” Spider webs are fascinating. Spider sex is
terrifying. To learn why and get a song stuck in your head all day, check out Trace’s
video here. Is learning how to mimic a spider web’s
ability to stretch worth the utter horror you experience every time you walk through
one in the dark?