Transcript
Indium tin oxide, which is currently used to make smart phone
screens, is brittle and expensive. The primary constituent, indium, is also a rare metal and is
ecologically damaging to extract. Silver, which has been shown to be the best alternative to
indium tin oxide, is also expensive.
But now a breakthrough from physicists at the University of
Sussex has combined silver nanowires with graphene - a two-dimensional carbon
material - to create new hybrid material, which matches the performance of the
existing technologies at a fraction of the cost.
On top of that, the new approach also promises devices that use
less energy, are more responsive, and do not tarnish in the air.
The way in which these materials are assembled is new. Graphene
is a single layer of atoms, and can float on water.
By creating a "stamp" - a bit like a rubber stamp - the
scientists can pick up the layer of atoms and lay it on top of the silver
nanowire film in a pattern.
The stamp itself is made from poly (dimethyl siloxane); the same
kind of silicone rubber used in kitchen utensils and medical implants.
While silver nanowires have been used in touch screens before,
no one has tried to combine them with graphene. The new process is unique in the way it puts the graphene layer
down.
The researchers float the graphene particles on the surface of
water, then pick them up with a rubber stamp, and lay it on top of the silver
nanowire film in whatever pattern they wish.
And this breakthrough technique is inherently scalable.
It would be relatively simple to combine silver nanowires and
graphene in this way on a large scale using spraying machines and patterned
rollers.
That means that brittle mobile phone screens may soon be a thing
of the past.
The addition of graphene to the silver nanowire network also
increases its ability to conduct electricity by a factor of ten thousand.
This means manufacturers can use a fraction of the amount of
silver to get the same, or better, performance.
As a result, screens will be more responsive and use less power.
Although silver is also a rare metal, like indium, the amount
needed to coat a given area is very small when combined with graphene.
Since graphene is produced from natural graphite - which is
relatively abundant - the cost for making a touch sensor drops dramatically.
Until now, one of the issues with using silver is that it
tarnishes in air.
The researchers found that the graphene layer prevents this from
happening by stopping contaminants in the air from attacking the silver.
They also saw that when the hybrid films are bent repeatedly the
electrical properties don't change, whereas you see "a drift" in the films
without graphene, which people have developed previously.
This research paves the way towards developing completely
flexible devices.
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