Home' Technology Review : September October 2006 Contents From the Labs
84 FROM THE LABS
TECHNOLOGY REVIEW /
suming with current technology. Many
researchers believe that a promising
way to represent "quantum bits"---the
basic units of quantum computation---
is to use ions, or charged atoms. The
ions are held in place with electromag-
netic elds produced by devices called
ion traps, and computations are then
executed by lasers, which manipulate
the behavior of the trapped ions. But
most existing ion traps have draw-
backs. Those that are easy to make can
manipulate ions in only one trapping
zone, which limits their computational
power; others that allow for more trap-
ping zones are di cult to mass produce.
The NIST trap is the rst that could po-
tentially address both problems.
METHODS: Using standard micro-
fabrication techniques, the researchers
built a trap that has a single layer of gold
electrodes; other types of traps have two
or three layers of electrodes, making
them more di cult to mass produce.
The electrodes create an electromag-
netic eld that isolates magnesium ions
and holds them in place 40 microme-
ters above the trap, where they could be
used to perform a computation.
NEXT STEPS: The team will con-
tinue to explore more-complex traps
that hold more ions. Future traps will
also have str uctures that allow the ions
to be manipulated with lasers in order
to perform logic functions, a key step
toward making quantum computers.
A new way to reduce friction could
make nanomachines practical
SOU RCE: "Atomic-Scale Control of
Friction by Actuation of Nanometer-Sized
Anisoara Socoliuc et al.
Science 313: 207--210
RESULTS: Researchers at the Uni-
versity of Basel, Switzerland, have
created a practical form of lubrica-
tion for nanoscale electromechanical
systems (NEMS) that reduces fric-
tion between the devices tiny mov-
ing parts 100-fold. The new method
is needed because liquid lubricants do
not work at the nanoscale, and other
dry approaches to reducing friction
have been too di cult to use in experi-
mental nanomechanical devices.
WHY IT MATTERS: Some of the most
promising nanotechnologies involve
micro- and nanoelectromechanical
devices, including microscopic mir-
rors for communications routers and
ultradense computer memory that uses
the tip of an atomic force microscope
(AFM) to write data bits. But friction
can cause the mechanical parts in these
devices to wear out too quickly, limit-
ing their commercial use.
METHODS: When researchers move
a microscopic tip across a surface to
make nano features, friction causes
the tip to alternately stick and slip. The
Swiss team eliminated this problem by
vibrating the tip of a silicon AFM probe,
reducing the friction between it and test
surfaces of sodium chloride and potas-
sium bromide. The application of this
technique would be straightforward
in AFM-based memory; other NEMS
devices could incorporate small oscilla-
tors to vibrate parts that might stick.
NEXT STEPS: The researchers re-
cently tested their method on oxidized
silicon in air, and initial results suggest
that it works. But they still need to apply
the technique to existing devices.
Novel coatings could make safer
implants, help build organs
SOU R C E: "Controlling Interlayer Diffusion
to Achieve Sustained, Multiagent Delivery
from Layer-by-Layer Thin Films"
Kris C. Wood et al.
Proceedings of the National Academy of
Sciences 103(27): 10207--10212
RESULTS: By developing a way to seg-
regate components in ultrathin surface
coatings, MIT researchers have made
a new class of materials that can release
dr ugs, and even genes, in an exact
sequence and at a predetermined rate.
WHY IT MATTERS: Coated with the
new materials, medical implants such
as arti cial hips could prove safer and
more e ective than their predeces-
sors, releasing rst antibiotics and then
growth factors and other drugs exactly
where and when they are needed.
E orts to engineer complex tissues
such as bones, blood vessels, muscles,
and livers could also bene t from scaf-
folds coated with the new materials,
which could encourage the growth of
speci c cell types.
METHODS: The researchers dip a
surface to be coated into a series of
solutions alternately containing poly-
mers of one charge and drugs or dr ug
carriers of the opposite charge. These
layered coatings will break down in
water, freeing their contents. To pre-
COURTESY OF ANISOARA SOCOLIUC, UNIVERSITY OF BASEL
Friction is reduced when the tip
of an atomic force microscope
is vibrated as it moves across a
surface. Red represents areas
of high friction, blue low.
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