The Littlest Chainsaw

Date: Thu Jan 17 2002 - 09:33:10 MST

World’s Smallest Microchain Drive Fabricated At Sandia

ALBUQUERQUE, N.M — A microchain that closely resembles a bicycle chain —
except that each link could rest comfortably atop a human hair — has been
fabricated at the Department of Energy’s Sandia National Laboratories.
(The distance between chain link centers is 50 microns. The diameter of a
human hair is approximately 70 microns.)

Because a single microchain could rotate many drive shafts, the device would
make it unnecessary to place multiple tiny microelectromechanical (MEMS)
motors in close proximity. Usually, a separate driver powers each MEMS

“All those drives take up a lot of real estate on chips,” says Sandia
technician Ed Vernon, who has received a patent for the silicon microchain.

The microchain also makes it possible to drive a MEMS device from a motor
situated at a distance, again saving considerable space on the MEMS-bearing

The microchain, says Ed, could be used to power microcamera shutters, as
larger chains currently do in the macroworld. It could also be used in
mechanical timing and decoding.

The 50-link silicon microchain is designed to transmit power somewhat like
the drive belt in a 19th-century sewing factory. There, a central engine
shaft powered by steam turned drive belts to power distant work stations —
for example, sewing machines — before the dawn of the age of electricity.

Chain systems, unlike stroke systems, do not require back-and-forth movements
but instead allow for both continuous and intermittent drive translation.

Vernon fabricated a microchain rather than a microbelt because although
silicon belts are tough and flexible, they are spring-like and produce too
much torque on gears not aligned in a straight line. Each chain link, on the
other hand, is capable of plus-or-minus 52 degrees rotation with respect to
the preceding link, without creating pressure on the support structure. The
wide angle means MEMS designers can be relatively unconstrained in
positioning multiple devices.

The longest span unsupported by gears or bracing is 500 microns. A microchain
tensioner is needed to accommodate longer spans.

The multilevel surface-micromachined silicon device was constructed with the
aid of Sandia’s patented Summit IV and Summit V technology, which enables
construction of complicated MEMS devices.

This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 13:37:35 MST