State of the Art
Tiny Forces to Be Reckoned With
Researchers at the National Institute of Standards and Technology
give more than a fig about newtonsthe international unit for
measuring force. A new five-year initiative aims to develop an
electronic method that can accurately measure the feeblest of
forces, down to billionths of a newton (nanonewton).
A nanonewton is equal to the force exerted by a single blood cell
in the Earths gravitational field. Much of the push for tools
to measure such micro forces comes from the data-storage industry
and two fast-developing areas: nanotechnologythe realm of almost
infinitesimal devicesand microelectromechanical systems, MEMSsemiconductor-like
hybrids that combine electronic and mechanical devices on a chip.
Both technology areas will leverage slight forces with great effect,
propelling tiny robots, for example, that inspect pipes or remove
plaque from veins and arteries.
Small, unwanted forces may wreak havoc, however. Larger-than-anticipated
stresses could cause surface cracks that disable a device or knock
a MEMS machine out of service.
NIST researchers say they might be able to push current capabilities
to measure forces down to 10 millionths of a newton. But their
goal is to deliver highly accurate measurements of forces that
are about 10,000 times smaller. Preliminary work points to a promising
method for standardized measurements of micro forces: developing
the electronic equivalent of a nanonewton by comparing a known
electric current in a coil with the mass of an object in a gravitational
ASTM Committee E-8 on Fatigue and Fracture is working on standards
related to MEMS. See the November 1999 issue of SNThe Big Problem with Small Failures. //