Physics News Update -- Number 660, November 4, 2003
by Phillip F. Schewe, Ben Stein, and James Riordon
Ref: http://www.aip.org/physnews/update/

Micro-Origami Fabricated Micromirrors

Microelectromechanical systems (MEMS) are becoming increasingly
important as researchers develop miniaturized mechanical devices for
communications, biotechnology, and a variety of measurement
applications. Often these machines include hinged parts that must be
set in place before operation, which can lead to challenging and time
consuming manual manipulation of components at ever decreasing scales.
Recently, researchers from the ATR Adaptive Communications Research
Laboratories in Japan proposed a technique that they call micro-origami
to fabricate MEMS devices that automatically move into position. The
group has now tested the technique, in collaboration with researchers
at Konan University and Osaka City University, by creating hinged
micromirrors that lift themselves up following the final fabrication
stage. The key to the micro-origami technique is to manufacture hinges
out of a pair of material layers with slightly different atomic
spacings. This lattice mismatch causes a stress that in turn bends the
hinge (see figure) and, in this case, raises a mirror above the
substrate. (The effect is reminiscent of the bimetallic strips in some
thermostats, which consist of bonded layers of metals that expand at
different rates when heated, leading to stresses that bend the strips
as temperatures change.) Once a mirror was in place, the researchers
could move it on its hinge by illuminating the mirror with a high power
argon laser. It is not yet entirely clear what mechanism caused the
illuminated mirror to move; the force due to radiation pressure, in
particular, was too small and in the wrong direction to account for the
effect. Nevertheless, the researchers (Jose M. Zanardi Ocampo,
81-774-95-1582) were able to use the motion of the micromirror to
control the position of a reflected helium-neon laser beam.
Potentially, the micro-origami mirror could lead to optical MEMS
switches or other small devices that automatically pop into place
without human or mechanical intervention, dramatically speeding and
simplifying construction of miniature machines. (J. M. Zanardi Ocampo
et al., Applied Physics Letters, 3 November 2003)


Acceleration Disrupts Quantum Teleportation

Acceleration disrupts quantum teleportation, a new study has shown
(Paul Alsing, University of New Mexico, 505-277-9094). In quantum
teleportation (see PNU #350), researchers create a pair of particles
(such as photons) and cause them to interact so their properties become
interrelated (a process called "entanglement").

Subsequently, after the particles go their separate ways, one can send
the first particle of the entangled pair and a new, third particle to a
detector simultaneously, and make a "joint" measurement of the
particles' properties (such as the directions their electric fields are
wiggling). Measuring these particles disturbs them, so as to reduce the
amount of information that an experimenter can obtain about their
properties. The measurement therefore produces just a limited amount of
ordinary, "classical" information.

But since the two entangled particles are interlinked, the measurement
also affects the properties of the second, remote particle in the
entangled pair. This "nonlocal" effect can be understood as a transfer
of "quantum" information from the first to second particle.

When the experimenter who handled the first particle contacts the
experimenter handling the second particle with the limited "classical"
information that he or she obtained from the measurement (a process
that can take place only at light speed or slower), the latter
experimenter has enough information to manipulate the second particle
in just the right way as to produce the exact quantum properties of the
(now destroyed) third particle.

This process of transference of quantum properties between particles,
by means of quantum measurement and classical communication, even if
the particles are light years apart, is called quantum teleportation,
and intimately relies upon the fact that the pair of particles are
interlinked or "entangled" through the unusual rules of quantum
physics. Quantum teleportation is different from Star Trek
teleportation in that real-life physicists are only teleporting a
particle's properties, rather than the particle itself.

Drawing from the example above, a new analysis has shown that quantum
teleportation would malfunction if the receiver of the second particle
is accelerating relative to the third particle. (Coincidentally,
spaceships in Star Trek usually don't teleport crew members when they
accelerate into warp drive.)

The disruption to quantum teleportation arises from the Davies-Unruh
effect (see Physical Review Focus article), in which acceleration, even
in empty space, creates a bath of hot particles resulting from the
energy of the acceleration. This thermal bath of particles inextricably
disrupts the receiver's ability to perfectly recreate (with the second
accelerated particle) the properties of the third (unaccelerated)
particle that have been teleported from the sender.

While this effect is small for typical accelerations in Earthly labs
the result shows an interesting relationship between the effects of
space-time motion and the quantum world. (Alsing and Milburn, Physical
Review Letters, 31 October 2003)


A Close Look at Hagfish Slime

Hagfish are primitive, eel-like fish that are nearly blind and lack
jaws or true vertebrae. One thing they do have is the unnerving ability
to produce copious amounts of slime when disturbed. Researchers from
the Cambridge Polymer Group in Boston and the University of British
Columbia are now taking a close look at hagfish slime, in an attempt to
understand how the slime protects the fish in nature and to determine
if the slime could lead to practical materials for industry or
medicine. Hagfish slime is a concoction of mucus and threadlike fibers,
and is produced in concentrated form from a series of pores that line
the sides of the fish's body. Upon contact with seawater, the
concentrated slime expands into a sticky gel that can ensnare and
sometimes suffocate an attacker. Unlike the mucous produced by the
membranes of humans and other animals, which functions best at body
temperature, the researchers (Gavin Braithwaite, 617-629-4400, Douglas
Fudge) found that the properties of hagfish slime are relatively
temperature independent over a broad range (from roughly 5 to 30
degrees Celsius). The insensitivity to temperature ensures that slime
is an effective defense in a variety of conditions, and also suggests
that artificial materials that mimic hagfish slime chemistry might make
good space-filling gels. One potential application for such gels,
explain the researchers, is as a way to curtail bleeding in an accident
victim or during surgery. In addition, studying the slime may help us
understand how mucins, the components of mucous, function in our own
bodies and elsewhere. There is currently some debate regarding the
relative importance of the fibers and the mucous in the material
properties of hagfish slime. The recent research, which was presented
earlier this month at the 75th Annual Society of Rheology meeting in
Pittsburgh, focused on characterizing the properties of the mucous
after the fibers had been removed from the slime.

Physics News Update is a digest of physics news items arising from
physics meetings, physics journals, newspapers and magazines, and other
news sources. Subscriptions are free as a way of broadly disseminating
information about physics and physicists. Feel free to post it where
others can read it; please credit the American Institute of Physics.
Physics News Update appears approximately once a week. Questions?
Contact the editors at .

Sam Wormley wrote:

Physics News Update -- Number 660, November 4, 2003
by Phillip F. Schewe, Ben Stein, and James Riordon
Ref: http://www.aip.org/physnews/update/

Hagfish slime is a concoction of mucus and threadlike fibers,
and is produced in concentrated form from a series of pores that line
the sides of the fish's body. Upon contact with seawater, the
concentrated slime expands into a sticky gel that can ensnare and
sometimes suffocate an attacker.
[snip]

I find the threads to be astonishing. They are perfectly packed into
near-microscopic spheres that open and unreel outrageous lengths of
thread without tangling. Then the expanded threads tangle in the
mucous and there is no dealing with the fiber-reinforced goo. The
hagfish itself has a unique mechanism for clearing itself of the stuff
- and it's a chiral manipulation! Somebody should do stats on
handedness directions.

"Secrets of the Slime Hag," by Frederic H. Martini ["Scientific
American" October 1998]

I seem to remember an earlier article, or maybe one in "Science" or
"Nature."

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!