Your news round-up from the big world of the incredibly
small. November 2000 edition
Diamonds are what nanotechnologists
really want to build their little machines from. We won't be able to see
them, but they'll be used to make the devices that today are science fiction
like medical micro-robots and microscopic computers. Here and today, devices
have already been made from diamond (as reported in the
March
SmallTalk) but it has been hard going. We have the technology to carve
diamond on a small scale, but only when it's nice and thin. Our thin diamond
films have been made from relatively large crystals, and as our carving
attempts split the film up along the crystal edges, our diamond creations
to date have somewhat chunky margins.
Building
from hard-wearing diamond is better than building little machines using
silicon chip technologies because silicon just wears away too quickly.
But we could carve silicon more accurately and so silicon Micro Electro-Mechanical
Systems(MEMS) were the norm.
Dieter
Gruen of the Argonne National Laboratory
(who kindly supplied these pictures) and Alan Krauss have developed a way
of converting "buckyballs" (balls of 60 carbon atoms) into a thin, regular
diamond film with interlinked crystals only a few tens of atoms across.
They can either be etched far more accurately than the older diamond films
like the vernier calipers on the left, or can be grown over a silicon mould
which is later dissolved. That's how the tube on the right was created.
It is 5 thousandths of a millimetre across and has solid diamond walls
only 300 nanometres thick. For his work, Gruen was presented with the MRS
Medal award by the Materials Research Society. He has also made a significant
progress towards making widespread micro- and nanoscale machines a reality.
Propellerheads
A team from the Montemagno Research Group at Cornell
University has succeeded in making a very small motor indeed. By taking
the proteins out of the wriggly bits on bacteria and clustering them around
the shaft of a bent microscopic nickel wire, they can make the wire hoon
around like a propeller at 8 revs a second. The protein bits sit atop a
nickel post only 80nm in diameter, which is less than half the size of
the smallest feature on the best Pentium computer chip. The whole thing
is powered by the same chemical that the human body uses: ATP. The motors
automagically self-assemble when the bits are mixed together, but out of
400 sets of bits only five worked. Room for improvement, A for effort.
One day things like this will be whizzing around inside our cells, fixing
us up, keeping us young, and curing hangovers.
Toughest At The Top Or Bottom?
There are two ways of making nanomachines: Start big and try to work down,
or start with atoms and try to work up. Gruen's diamond films are an example
of big things that make smaller bits. Chemists join atoms together in bulk,
reacting beakers of chemicals to form more complicated chemicals, or occasionally
noise, light and smoke.
But making just one atom react with another is tricky: Not only do
you have to be very delicate, but you also have to see what you're doing.
A tool called an AFM that senses the electricity conducted through a single
atom can be used to find and move them one at a time. By pushing small
molecule of carbon monoxide gas (the poison in car exhausts) around a firmly-anchored
surface with iron in it, nanotechnology researchers have managed to make
the carbon monoxide react with the iron.
But
in the last couple of months things have progressed to the point where
German
researchers have pushed around two little molecules of iodobenzene,
broken their iodine tips off, and electrically welded the two big bits
together with considerable accuracy to form a single molecule of biphenyl
(used in these parts to preserve citrus fruits).
A ridge in an otherwise perfect copper surface is used to help hold
the bits still in the same way that a welder uses a piece of firebrick
to lean parts agains while welding them. As with the welder, it should
be possible to flip the finished part around and weld on new bits at an
angle to the original join to form a structure that extends in three dimensions.
Alternatively, unwanted bits could be broken off a larger molecule to leave
the shape we wanted. Most importantly, this shows to all the nay-sayers
who claim that nanotechnology won't work because it's impossible the build
molecules one at a time that they are plain wrong.
So as the people working from the bottom up make bigger bits, and the
people working from the top down make more precise machines, the gap between
the two fields gets smaller. Once they meet in the middle, lessons learned
in the one field will be applied in the other and the rate of our progress
and understanding will increase dramatically. This is why I believe that
sophisticated nanotechnology devices like assembly tools and molecular
computers will become a reality within a decade.
A Taste of The Future
A new buzzword is going around in boffin circles: 3D Printing. You might
have seen it on those grisly medical TV shows where they call it 'stereolithography'
and use it to make yellowy plastic models of distorted skulls from the
image of a CAT scan.
It is a horrendously expensive process, but the yellow plastic stuff
invented in 1984 is not the only way to do the job. Cheaper versions use
a small industrial laser to cut shapes out of sticky paper, and then stick
the layers together to make a 3D object out of something that looks and
feels like fine-grained wood. There are even companies like Toybuilders
(http://www.toybuilders.com) who
will make toys, models, golf club heads, models of your unborn baby and
anything else to your design.
More recently the humble inkjet printer has been drafted in to use
thick inks and layer them one on top of another. By using some thick, water-based
ink too, you can support delicate parts during production and then wash
away the supports. You can use different coloured inks, metallic inks,
inks with electrical properties to print circuits, chemicals to build medical
tests on a card, batteries, MEMS, all kinds of weird stuff.
NASA and the US millitary have developed versions that print with clay
'slip' (muddy water to those of us who aren't potters) onto a hotplate.
The hotplate dries the clay as it gets squirted out. Metal powder can be
squirted in as well in varying proportions and the whole lot fired off
in a kiln. You then end up with a part that is ceramic at one end and metal
at the other. And you can make it in the back of a jeep, so you don't need
to take all the spare parts for a tank into battle, or all the spares for
a space station into space; just download the file from the internet and
print it.
The cool part for us is that machines like this could be made for about
NZ$3,000 with current technology, and you can bet that someone somewhere
is working on that one. It's not as powerful as nanotech, but can you think
of something to print with it?
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