at the Massachusetts Institute of Technology (MIT) have been working
on giving fibers more elaborate properties over the past decade and
have finally succeeded in doing so with their most recent discovery:
Fibers that can interact with their environment by producing
and protecting sound.
fibers were discovered by associate professor of Materials Science
and principal investigator at MIT's Research Lab of Electronics Yoel
Fink, along with his collaborators. The
study was published in the August issue of Nature
and featured on their website on July 11. Other authors of the study
include Shunji Egusa, Noémie Chocat
and Zheng Wang.
newly developed fibers, known as acoustic
fibers, acquire their functionality from the geometrical
pattern of many different materials and have to endure the heating
and drawing process while remaining intact. Regular optical fibers
are made from a "preform," where it is placed in a large
cylinder of a single material and heated up, drawn out, and cooled.
is most commonly found in microphones lies at the center of the
acoustic fibers. Researchers make this plastic "piezoelectric"
(meaning that applying an electric field causes it to change shape)
by making sure that the molecules remained lopsided within the
fluorine content (even during heating and drawing) where fluorine
atoms lined up on one side and hydrogen atoms lined up on the other
side. The electric field in a traditional piezoelectric microphone is
generated by metal electrodes, but in the case of this fiber
microphone, metal electrodes would lose their shape during the
drawing process. To stop this from happening, Fink and his
researchers used a conducting plastic with graphite, and when heated,
the conducting plastic upholds a higher viscosity than metal, which
prevented the mixture of materials.
drawing the fiber, researchers aligned the piezoelectric molecules in
the same direction by using a powerful electric field that is 20
times as strong as fields that produce lightning in a thunderstorm.
If a fiber is too thin in any particular area, the electric field
generates a small lightning bolt that could destroy its surrounding
material. This is a very fragile balance that researchers had to
control, but were finally able to create functioning
and his fellow contributors measured the fibers' acoustic properties
closely by putting them in a tank of water (since water conducts
sound better than air) "opposite a standard acoustic
transducer," which can emit sound waves both detected by the
fiber and emitted by the fiber.
can actually hear
them, these fibers," said Chocat. "If you connected
them to a power supply and applied a sinusoidal current (an
alternating current whose period is quite regular), then it would
vibrate.And if you make it vibrate at audible frequencies and put it
close to your ear, you could actually hear different notes or sounds
coming out of it."
addition to sound sensitive fibers, MIT has developed camera-like
fibers that are sensitive to light. They are a mesh of
fibers that can detect two frequencies of light and will produce
signals that "when amplified and processed by a computer,"
reproduce images near the mesh.
fibers can be used for wearable microphones, biological sensors,
large-area sonar imaging systems with high resolutions and loose nets
that monitor the flow of water in the ocean.