Low power motion sensor based on microchip technology
A University of Florida engineer has developed a small, easy to
manufacture motion sensor that could help popularize the sensors as standard
equipment in personal electronics, medical devices and other applications.
The sensor, which measures about 3 square millimetres or one-tenth of an
inch, is not the smallest motion sensor ever invented, but it is extremely
sensitive, drawing only a tiny amount of electrical power. It is also one of
a new generation of sensors that can be made using the computer chip
manufacturing industry’s standard techniques and equipment.
|That means that in the near future
“the application range can be expanded a lot,” said Huikai Xie,
a UF assistant professor of electrical and computer engineering.
Xie is one of five authors of a paper describing the sensor that
appeared in the December issue of the journal Institute of
Electrical and Electronics Engineers Transactions on Circuits
Huikai Xie, a University of Florida assistant professor of
electrical and computer engineering, examines a tiny motion
sensor that he and two graduate students recently designed. The
sensor, located at the center of the device in Xie's hand, is
about 3 square millimeters, or one-tenth of an inch.
Motion sensors are hardly new, but they were large, heavy and typically
used in airplanes and ships for navigational purposes in recent decades.
Miniaturization techniques developed as part of a relatively new field
called Micro Electrical Mechanical Systems, or MEMS, have steadily reduced
their size and cost.
The result is that the sensors are steadily becoming commonplace in
commercial products. Today’s cars, for example, contain tiny accelerometers
that deploy airbags after sensing the sudden stops or changes in motion that
occur during collisions. A small number of cell phones, personal digital
assistants and laptops also now carry motion sensors, said Dave Monk, the
manager for sensor operations at Freescale Semiconductor, the nation’s
third-largest chip manufacturer.
They have several functions, he said. In PDAs, they may allow users who
are reading a book to “turn the page” by simply turning the PDA over in
their palm and then turning it back again, he said. And in cell phones, the
motion sensors may sense when the phone has been dropped and shelter the
hard drive to prevent memory loss.
Xie believes these sorts of applications are only the beginning. Cheap,
tiny, easily made and paired with wireless technology, motion sensors could
be easily worn or even sewn into clothes, he said. That could help coaches
zero in on the movements of athletes, or nurses working at a distance
monitor elderly people in their homes.
It’s even possible that the sensors could be implanted in bones during
surgeries, giving orthopedic surgeons a unique way to monitor the progress
of repairs, he said.
These developments have been stalled by high costs because many of the
tiniest sensors developed so far require new or nonstandard manufacturing
technology. Xie and other UF team members, including doctoral students
Hongwei Qu and Deyou Fang, sought to solve this problem in their new
In a three-year-old project originally funded with a $170,000 grant from
NASA, they developed a single-chip sensor that can be manufactured using
Complementary Metal Oxide Semiconductor technology, the industry standard
for silicon chip manufacturing.
The chip uses about one-thousandth of a watt of power, meaning it has the
potential to operate for as long as a year on a standard watch battery. It
is also extremely sensitive, so much so that it can register sound as well
Although developing the first few sensors was expensive, Xie estimated it
could cost $10 or less if mass produced. He and his graduate students have
installed several sensors in a cigarette pack-sized board of electronics to
test their capabilities. UF also is pursuing a patent on the sensor.
“Eventually, you can wear all kinds of sensors with you to monitor
everything you want to know — your heartbeat, your blood pressure or even
something like your glucose concentration,” Xie said. “I think this is a
very interesting, exciting field that will eventually help people live much
higher quality of life.”