Qualia Schmalia...here's news for nerds
Check your links to BBC On-line sci/tech!
Scientists at the US Department of Energy's national security facility have
created a micro-machine etched from amorphous diamond, the hardest material
in the world after crystalline diamond.
The methods used were the same as those used with current silicon chip
manufacturing techniques.
The first diamond micro-machine is a comb drive whose tiny teeth move forward
and back as an electrical current reverses constantly between positive and
negative. The teeth are just two thousandths of a millimetre apart.
The researchers, at the Sandia National Laboratories in New Mexico, say
diamond has a number of valuable properties.
Resistant to wear
Its resistance to wear makes diamond ideal for micro-machines that need to
function for extended periods of time.
"One estimate in the literature claims that diamond should last 10,000 times
longer than polysilicon," said group member Tom Friedmann.
Diamond should last 10,000 times longer than polysilicon
Tom Friedmann, Nanotechnologist
Also, diamond is less susceptible to "stiction" than silicon. Stiction - a
combination of stickiness and friction - can render micro-machines useless.
This is because silicon is attracted to water, which acts as a kind of glue.
Diamond does not have the same problem.
Another advantage is that diamond is biologically benign. A micro-machine
such as a tiny drug dispensing unit could be used in the body without
triggering an allergic reaction.
There are two kinds of diamond, crystalline and amorphous. The Sandia
researchers used amorphous diamond because crystalline diamond needs far
higher temperatures to synthesise it, and also its surface roughness makes it
unsuitable for micro-machines.
Amorphous diamond itself had been impractical because its tremendous internal
stresses had made it impossible for the material to stand alone or to coat
thickly any but the strongest surfaces.
However, a process developed by Friedmann and Sullivan eliminated that
problem.
Silicon MEMs (MicroElectroMechanical Systems) are already used in a variety
of applications, ranging from air bags in cars to optical micro-mirrors
intended for possible deployment on satellites.
It's hoped that diamond MEMs could eventually offer a harder wearing and more
flexible alternative, and in the future could replace silicon micro-machines
completely.
This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 14:04:08 MDT