TECHFOCUS
This section was edited by
Associate Editor Jeffrey Winters.
Instrumentation & Control
MICROSENSORS DON’T NEED A LOT OF POWER, BUT SUPPLYING IT TO THEM IN REMOTE ENVIRONMENTS CAN BE
PROBLEMATIC. It might not take much of a battery to
run a device that, say, monitors the strain on
a bridge, but sending a technician to replace that battery would be prohibitively expensive.
Researchers at the University
of Michigan in Ann Arbor may
have developed a solution. They
+ Peppercorn-Scale Power
collection, cutting down on power consumption is a key. The
sensor system uses an ARM Cortex-M3 processor, which is
designed to use far less energy in sleep mode than standard
processors. To help stretch the power supply even farther, the
sensor spends most of its time in sleep mode, waking only
every few minutes, and then only long enough to take a quick
reading before returning to sleep.
The processor requires 0.5 V to operate, which is less than
the battery used in the system supplies. To get the most efficient use of the battery power, the researchers changed the
setting on the power management unit’s clock, essentially
slowing down the system.
This tiny device combines a solar cell, a battery, and a microprocessor. The unit draws less than 1 nanowatt.
have produced an energy-har-vesting system that combines a
solar cell, battery, and associated electronics that occupies less
than 10 cubic millimeters.
With such a small area for solar energy
The result is a sensor system that can operate on an aver-
age of less than 1 nanowatt.
UNIVERSITY OF MICHIGAN
ONE PHOTON AT A TIME
Makers of high-end digital cameras boast about the ability to capture images in dim lighting. But
none can match the light-catching
prowess of a machine constructed by
researchers at the National Institute
of Standards and Technology in
Boulder, Colo. According to a paper
presented in April, the detector was
capable of counting individual photons of light as they passed through
a fiber-optic cable, and did so with a
99 percent efficiency rate.
The ability to count photons might
not seem very important—a photon
of visible light packs about a billionth of a billionth of a joule—but
for researchers working to make
quantum computers a single photon
can carry useful information. And
engineers trying to devise ways to
defend against tapping fiber-optic
lines could count photons to see if
any were missing.
The NIST photon detector uses a
superconducting material to act as a
temperature gauge. Each photon that
strikes the material and is absorbed
raises its temperature ever so slightly.
As a consequence of this change in
temperature, the electrical resistance
of the material is increased. It’s this
change in the electrical property that
enables the device to register photons.
The team had reported in 2005
a similar detector with 88 percent
efficiency. The increased efficiency
of the new detector is due to a better
alignment between the superconducting material and the fiber-optic
line providing the photons. Indeed,
the 99 percent efficiency rate is an
estimate. The mechanism for producing photons is more error-prone
than the detector itself.
MOLECULE SNAPSHOT
Hydrogen peroxide is a chemical that causes cell damage—damage that causes hair to bleach, for
instance. But it has also been found
to play a role within cells, as a sig-
naling molecule in a pathway that
stimulates cell growth.
