Five wonder materials that could change the world
Materials
such as graphene and shrilk are so new that the scientists who discovered them
hardly know what to do with them – they only know they might yet transform our
lives
"The
history of materials is a history of mistakes," says Mark Miodownik, a materials scientist at University College
London, who traces his own fascination with materials to the moment he was
stabbed in the back with a razor while ambling to school one day.
The
remark is spot on. Over the centuries, scientists have been as likely to
stumble on the next wonder material during a botched experiment as to create it
from scratch on purpose. The tradition continues today: more than one material
tipped to revolutionise the world, or at least give us better gadgets, came
about through serendipity, if not outright blunders.
But
the chance discovery of useful materials might not carry on for much longer.
Scientists are now turning to computers to design materials and work out their
properties before going anywhere near a laboratory or workshop. Some of the
newest materials that are getting scientists fired up exist only in theory. The
goal now is to make them a reality.
The
materials here are so new that their ultimate applications are still tentative
– or not even being guessed at. But each has the potential to be
transformative. If the history of materials is any guide, how we eventually use
them will, in part, be discovered accidentally, too.
Graphene
The
Friday evening antics that led to the invention of graphene have become the
stuff of scientific legend. Andre Geim and Konstantin Novoselov at Manchester
University were playing around with Scotch tape and a lump of graphite when
they found they could make sheets of carbon one atom thick. That was in 2004.
They have since shared the Nobel prize, become Sirs and been rewarded with a
£61m National Graphene Institute.
And
all for good reason. Graphene is an extraordinary material. Apart from its many other
properties, it's immensely strong, flexible, transparent and conductive. This
makes it perfect for the next generation of electronic devices, the sort that
might be sewn into our clothing, slapped on drinks bottles and cans of food or
rolled up and tucked in our pockets. Last week, Zhaohui Zhong at the University
of Michigan described how graphene might be used to make night-vision contact lenses.
"Graphene has huge potential," says Andrea Ferrari,
director of the Cambridge Graphene Centre. "You don't usually
find a material that has applications in so many different areas."
The
money has poured in. The EU has set aside a billion euros to help researchers get
graphene out of the lab and into products. George Osborne has called it a
"great British discovery" and backed its commercialisation. Companies have sprung up
that make graphene to order. With graphene, everything from your fridge to your
toothbrush could be hooked up to the internet. "How do you enable the
Internet of Things? You need to put devices in everything. But you can't put a
Pentium 5 processor in a book; it'll cost more than the book," says
Ferrari. "The Internet of Things will need very cheap, simple, flexible
and eventually disposable devices, and that's where graphene comes in."
Spider silk
Long,
long ago, in the history of science, there was a time when researchers didn't
speak of spider silk as the perfect material from which to manufacture bulletproof
vests.
The application was touted around after researchers teased out the silk's
molecular structure and from that came to understand its fantastic strength and
flexibility.
Decades
on, the prospect of a vibrant market for personal body armour spun from spider
silk probably overestimated the dangers of modern life as much as the practical
hurdles that come with using the material.
"You
can't use spider silk to make a bulletproof vest. It's too extensible. It would
catch the bullet, but not before the bullet had passed through your body,"
says Fritz Vollrath at the Oxford Silk Group. The words of caution don't end there.
"Can you use it as a material? Probably not. It has to be collected from a spider, and that's not
economically feasible."
And
yet scientists remain fascinated. That's because it's an exquisite material to
learn from and will, Vollrath says, inspire researchers to make better
materials in the future. Spider silk is made from a biopolymer called an
aquamelt, which can be spun at room temperature 1,000 times more efficiently
than plastics that need to be heated up and cooled down. By controlling the
rate at which the silk is spun, a spider can control the stiffness or flexibility
of the fibres. The goal for researchers is to make other materials that mimic
spider silk's tricks.
Metamaterials
Harry
Potter. Cloak. Invisible. Full house! Metamaterials bingo remains –
inexplicably – a niche hobby, but there is no doubting the genuine excitement around the materials. They owe their existence,
in large part, to the enormously competitive microchip industry, which has refined
manufacturing at the nano scale. Metamaterials are made with the same
technology, but their design is so precise that scientists can control how
electrons inside the materials respond when light – or other electromagnetic
waves – strike them. This makes it possible to manipulate radiation like never
before.
And
yes, metamaterials can – to some extent – bend light around an object,
rendering that object invisible. "You have to structure the material on a
length scale that's short compared to the wavelength you're interested in, so
for visible light that means on the nano scale," says Chris Phillips at Imperial College's physics department, where much of the work on
cloaking devices has been pioneered.
The
materials themselves vary. To control radiowaves, you can use copper and
fibreglass. To make metamaterials that bend infrared light, you can use
semiconductors. Cloaking devices are still little more than party tricks, but
that's changing. Objects can be hidden at some wavelengths and not others, or
only under specific conditions, such as with polarised light, or from a
particular angle. It's unlikely a cloak will ever make something completely
vanish: even if an object is invisible to the naked eye, there's always radar
and infrared imaging to turn to. "As a general rule, an object that's invisible
at one wavelength will be visible at another. You can make a cloak work across
a range of wavelengths, but not the whole electromagnetic spectrum," says
Phillips.
Shrilk
What
to call a material made from leftover shrimp shells and proteins derived from silk? Javier Fernandez and Don
Ingber at the Wyss
Institute at Harvard
plumped for shrilk, and the name has stuck.
Shrilk
was inspired by research into the tough skins of insects. The coating is made
from layers of a material called chitin and a protein called fibroin. In one
arrangement, the material is strong and rigid enough to form the insect's
protective exoskeleton. What intrigued the Harvard group was that simple tweaks
to the material – specifically the amount of water bound inside it – changed
its behaviour dramatically. Without water the material is stiff, but with water
the coating becomes very flexible.
Don
Ingber, director at the Wyss Institute, left, and postdoc Javier Fernandez have
developed a new material called Shrilk. Photograph: Jon Chase/Harvard
University
Fernandez
and Ingber used fibroin from silk worms and chitosan, a material similar to
chitin, to make their first batch of shrilk. They then played with the water
bound inside the material to vary its properties. They can form strong,
transparent sheets of shrilk that are biodegradable and even enrich the soil
like a fertiliser as it breaks down. Bob Cunningham, also at the Wyss
Institute, says shrilk is an environmentally friendly alternative to plastics.
"It might not make sense to make the trash bin that you're going to use
for 10 years out of this material, but a trash bag you might fill up in a day
or a week that goes to landfill? That makes a lot more sense," says
Cunningham. The components are FDA-approved for use in the body, where they
could find a role as sutures, or scaffolds for growing new tissues that
dissolve when they are no longer needed.
Stanene
Stanene
is radical not only for its properties, but also for what it represents. Forget
accidental discoveries from lab tests gone wrong; this material was designed on
a computer, and its extraordinary behaviour worked out from theory. Only now
are researchers trying to make the stuff to see if it delivers on those
promises in the real world.
Stanene
was created – virtually, that is – by Shoucheng Zhang at Stanford University. Scientists call it a topological
insulator, but the name isn't wildly helpful. Stanene is an insulator on the
inside, and a conductor on the outside. Thin layers of stanene – or
one-atom-thick sheets of tin – are essentially all surface, and should conduct
electricity with 100% efficiency.
Materials
conduct electricity when electrons flow through them. However, in most
materials, the electrons are held up by impurities and other features that give
rise to resistance. This resistance generates heat, and so electronics must be
cooled to stop them melting. Stanene promises to change all that. The structure
of the material allows electrons to shoot along channels with no resistance
whatsoever. Add a little fluorine and, according to Zhang, the material will
have zero resistance at more than 100C (212F).
Zhang
sees stanene as the natural successor to copper interconnects in computers.
This might seem niche, but atomically thin connections that don't heat up would
enable designers to miniaturise electronics even more. Ultimately, Zhang says
stanene could replace silicon as a cheap and abundant material from which to
make computer chips.
Ian Sample http://www.theguardian.com/science/2014/apr/15/five-wonder-materials-graphene-shrilk-spider-silk-stanene-could-change-world
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