chain revs microdevices
Technology Research News
One gear in a mechanical wristwatch trips
another that sets in motion yet another, and it all happens in a fairly
small space. A researcher at Sandia National Laboratories has come up
with a tiny silicon chain that gets many much smaller gears going at once
in a much smaller space.
The tiny chain system resides on a computer chip, measures a single millimeter
from end to end, and works like a bicycle chain. Each of its 50 links
is 50 microns long, or about ten times the size of a red blood cell. As
a link moves, it catches on a gear tooth, which turns the gear.
The advantage of using a chain to move or rotate parts is that the parts
do not have to be close to the motor that drives the motion. A single
silicon chain can also drive several components in different locations
on a chip.
The idea for the chain came because the motors in Sandia's microscopic
shutter and gear mechanisms take up a lot of space, said Ed Vernon, a
design engineer at Sandia. "Currently our micro-engines can take
up to a third of the allotted real estate. I thought that if I could drive
multiple devices with a single engine more of the real estate could be
used for mechanical devices," he said.
Small chain systems are currently used in camera shutters and small machines.
"Microchains could have as many applications as conventional chains
as this technology progresses... the earliest applications might come
in the bio-medical area," said Vernon.
Each link can rotate plus or minus 52 degrees with respect to the link
preceding it. Since the joint between any two links is able to swivel
more than 90 degrees, "very sharp turns are possible as well as complex
threaded systems," Vernon said.
The prototype is 2.5 millimeters long but could be extended with the help
of a chain tensioner. "Chain systems are typically designed with
slack in them," said Vernon. A tensioner takes up the slack after
it starts moving and provides slack during high-torque starts.
The silicon chain is fabricated much like an integrated circuit, said
Vernon. He used alternating layers of doped silicon and oxide, then etched
away parts of the material to make the chain.
The machining challenge was in making a floating, unanchored device, said
Vernon. All the sprockets of the gears in this design are anchored to
a silicon wafer, but the links of the chain are not. "It is not common
for devices to be free of the substrate in surface micromachining,"
The work is remarkable, said Bruce R. Donald, a professor of computer
science and chemistry at Dartmouth College. "It is a technological
tour de force [and opens] up a wide range of new capabilities," he
The microchains could be used in many different kinds of dynamic micromachines,
Donald said. Applications could include micromachines that manufacture
tiny parts; a way of signing a document mechanically rather than electronically
for better security; and a closer study of the structure of molecules
like proteins, he said.
The chains could also be used in the field of biotechnology, "to
make implantable mechical devices for numerous applications," said
Vernon. "It is not too much of a stretch to imagine this chain as
a tiny chain saw. If you incorporate a vacuum, tumor removal could be
Sandia is in the process of licensing this technology to the public sector,
said Vernon. "If the technology is successful in the public sector
there could be a need for the chain within 2 to 3 years." For now,
the lab is planning to improve the reliability and packaging of the chains,
The work was funded by the Department of Energy.
Timeline: 2-3 years
TRN Categories: Microelectromechanical Systems (MEMS)
Story Type: News
Related Elements: Technical paper, "Surface Micromachined
Chain," presented at the "Workshop on Microsystems Technology & Applications,"
Tiny chain revs microdevices
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