Computers in your clothes?
A milestone for wearable electronics
Clothes that receive and transmit digital information are closer to
reality
Researchers who are working to develop wearable electronics have
reached a milestone: They are able to embroider circuits into fabric
with 0.1 mm precision -- the perfect size to integrate electronic
components such as sensors and computer memory devices into clothing.
Researchers who are working to develop wearable electronics have
reached a milestone: They are able to embroider circuits into fabric
with 0.1 mm precision -- the perfect size to integrate electronic
components such as sensors and computer memory devices into clothing.
With this advance, the Ohio State University researchers have taken
the next step toward the design of functional textiles -- clothes that
gather, store, or transmit digital information. With further
development, the technology could lead to shirts that act as antennas
for your smart phone or tablet, workout clothes that monitor your
fitness level, sports equipment that monitors athletes' performance, a
bandage that tells your doctor how well the tissue beneath it is healing
-- or even a flexible fabric cap that senses activity in the brain.
That last item is one that John Volakis, director of the
ElectroScience Laboratory at Ohio State, and research scientist Asimina
Kiourti are investigating. The idea is to make brain implants, which are
under development to treat conditions from epilepsy to addiction, more
comfortable by eliminating the need for external wiring on the patient's
body.
"A revolution is happening in the textile industry," said Volakis,
who is also the Roy & Lois Chope Chair Professor of Electrical
Engineering at Ohio State. "We believe that functional textiles are an
enabling technology for communications and sensing -- and one day even
medical applications like imaging and health monitoring."
Recently, he and Kiourti refined their patented fabrication method to
create prototype wearables at a fraction of the cost and in half the
time as they could only two years ago. With new patents pending, they
published the new results in the journal IEEE Antennas and Wireless
Propagation Letters.
In Volakis' lab, the functional textiles, also called "e-textiles,"
are created in part on a typical tabletop sewing machine--the kind that
fabric artisans and hobbyists might have at home. Like other modern
sewing machines, it embroiders thread into fabric automatically based on
a pattern loaded via a computer file. The researchers substitute the
thread with fine silver metal wires that, once embroidered, feel the
same as traditional thread to the touch.
"We started with a technology that is very well known--machine
embroidery--and we asked, how can we functionalize embroidered shapes?
How do we make them transmit signals at useful frequencies, like for
cell phones or health sensors?" Volakis said. "Now, for the first time,
we've achieved the accuracy of printed metal circuit boards, so our new
goal is to take advantage of the precision to incorporate receivers and
other electronic components."
The shape of the embroidery determines the frequency of operation of
the antenna or circuit, explained Kiourti. The shape of one broadband
antenna, for instance, consists of more than half a dozen interlocking
geometric shapes, each a little bigger than a fingernail, that form an
intricate circle a few inches across. Each piece of the circle transmits
energy at a different frequency, so that they cover a broad spectrum of
energies when working together--hence the "broadband" capability of the
antenna for cell phone and internet access.
"Shape determines function," she said. "And you never really know
what shape you will need from one application to the next. So we wanted
to have a technology that could embroider any shape for any
application."
The researchers' initial goal, Kiourti added, was just to increase
the precision of the embroidery as much as possible, which necessitated
working with fine silver wire. But that created a problem, in that fine
wires couldn't provide as much surface conductivity as thick wires. So
they had to find a way to work the fine thread into embroidery densities
and shapes that would boost the surface conductivity and, thus, the
antenna/sensor performance.
Previously, the researchers had used silver-coated polymer thread
with a 0.5-mm diameter, each thread made up of 600 even finer filaments
twisted together. The new threads have a 0.1-mm diameter, made with only
seven filaments. Each filament is copper at the center, enameled with
pure silver.
They purchase the wire by the spool at a cost of 3 cents per foot;
Kiourti estimated that embroidering a single broadband antenna like the
one mentioned above consumes about 10 feet of thread, for a material
cost of around 30 cents per antenna. That's 24 times less expensive than
when Volakis and Kiourti created similar antennas in 2014.
In part, the cost savings comes from using less thread per
embroidery. The researchers previously had to stack the thicker thread
in two layers, one on top of the other, to make the antenna carry a
strong enough electrical signal. But by refining the technique that she
and Volakis developed, Kiourti was able to create the new,
high-precision antennas in only one embroidered layer of the finer
thread. So now the process takes half the time: only about 15 minutes
for the broadband antenna mentioned above.
- ScienceDaily |