共用题干 New Understanding of Natural Silk's MysteriesNatural silk,as we all know,has a strength that ma...

共用题干
New Understanding of Natural Silk's Mysteries

Natural silk,as we all know,has a strength that man-made materials have long struggled to match.In a
discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough,MIT re-
searchers have discovered that silk gets its strength from its weakness.Or,more specifically,its many weak-
nesses. Silk gets its extraordinary durability and ductility（柔韧性）from an unusual arrangement of hydrogen
bonds that are intrinsically very weak but that work together to create a strong,flexible structure.
Most materials一especially the ones we engineer for strength一get their toughness from brittleness.As
such,natural silks like those produced by spiders have long fascinated both biologists and engineers because of
their light weight,ductility and high strength(pound for pound,silk is stronger than steel and far less brittle).
But on its face,it doesn't seem that silks should be as strong as they are;molecularly,they are held together by
hydrogen bonds , which are far weaker than the covalent（共价的）bonds found in other molecules.
To get a better understanding of how silk manages to produce such strength through such weak bonds,
the MIT team created a set of computer models that allowed them to observe the way silk behaves at the
atomic level. They found that the arrangement of the tiny silk nanocrystals（纳米晶体）is such that the hydro-
gen bonds are able to work cooperatively,reinforcing one another against external forces and failing slowly
when they do fail,so as not to allow a sudden fracture to spread across a silk structure.
The result is natural silks that can stretch and bend while retaining a high degree of strength.But while
that's all well and good for spiders,bees and the like,this understanding of silk geometry could lead to new
materials that are stronger and more ductile than those we can currently manufacture.Our best and strongest
materials are generally expensive and difficult to produce(requiring high temperature treatments or
energy-intensive processes).
By looking to silk as a model,researchers could potentially devise new manufacturing methods that rely
on inexpensive materials and weak bonds to create less rigid,more forgiving materials that are nonetheless
stronger than anything currently on offer. And if you thought you were going to get out of this materials
science story without hearing about carbon nanotubes（纳米碳管）, think again. The MIT team is already in
the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural
silk-like carbon nanotubes. Super-silks are on the horizon.