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Fish scales act as piezoelectric generator
To cite this article: 2016 Phys. World 29 (10) 5
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Yurii N Eroshenko
This content was downloaded from IP address on 26/10/2017 at 15:56
DASP/IDA; contex t: ESA/Roset ta/NavCam/CC BY-SA IGO 3.0
phy sic s wor
Fish scales act as
piezoelectric generator
Fish scales extracted from food waste have
been used to build tiny generators that can
convert mechanical energy – such as touch
or sound vibrations – to electrical energy. The
work was done by physicists in India, who say
that the piezoelectric device could be used to
develop environmentally friendly, self-powered
electronics with a wide range of applications.
Fish is a popular food in India and one possible
source of non-toxic piezoelectric materials is the
large quantity of fish scales that are disposed of
as waste. The scales are composed of collagen
nanofibrils, which are known to have piezoelectric
properties – a fact that inspired Dipankar
Mandal, a physicist at Jadavpur University in
Kolkata, India, and colleague Sujoy Ghosh to see
Nearly two years after it bounced onto the alien surface of comet 67P/Churyumov–Gerasimenko, Rosetta
if they could use waste scales to produce a costscientists have managed to locate the “final resting place” of their Philae lander. As the picture above shows,
effective, piezoelectric nano-generator (Appl.
Philae is wedged into a dark crack on the comet and the instrument’s orientation clearly reveals why
Phys. Lett. 109 103701).
establishing communications was so difficult following its crash-landing on 12 November 2014. The images
Collagen consists of three polypeptide
were taken on 2 September by the OSIRIS narrow-angle camera, as Rosetta came within 2.7 km of the surface.
chains that twist together to form a tripleA Rosetta Navigation Camera image taken on 16 April 2015 is shown top right for context, with the approximate helical structure. Hydrogen bonds between
location of Philae marked on the small lobe of the comet. As Physics World went to press, ESA revealed that
the polypeptide chains all orientate in the
Rosetta’s mission would end with a controlled crash into the Ma’at region of the comet on 30 September. The
same direction and act as molecular dipoles,
target area contains several “active pits” from which a number of the comet’s dust jets originate.
resulting in spontaneous electrical polarization
and piezoelectric properties. Within fish scales,
as they can be tracked back to their source, collagen nanofibrils self-assemble and align.
unlike surface-wave microseisms.
“We wanted to explore what happens to the
In their study, Kiwamu Nishida of the piezoelectric yield when a bunch of collagen
A new type of rare deep-Earth tremor, cre- University of Tokyo and Ryota Takagi nanofibrils are hierarchically well aligned and selfated by fast-developing ocean storms, has of Tohoku University looked at a spe- assembled in the fish scales,” Mandal explains.
been detected by researchers from Japan. cial kind of small, fast-developing extra-­
To build their device, the researchers washed
The signals from this kind of faint Earth tropical cyclone colloquially dubbed a and then treated fish scales – collected from
tremor – known as an “S-wave microseism” “weather bomb”. Seismic signals from a local market – with an acidic demineralizing
– may provide geophysicists with a new tool one of these storm events – which devel- solution to make them transparent and flexible.
to study not only oceanic storms but also oped in the North Atlantic between Ice- They then attached gold electrodes to these
land and Greenland in the December of flexible, transparent scales and laminated them
the Earth’s interior.
First observed in the 1940s, microseisms 2014 – were recorded on the Japanese with a polypropylene film to create a robust “bioare faint Earth tremors generated by the High Sensitivity Seismograph Network. piezoelectric nano-generator”. Tests showed that
sloshing of ocean waves on the sea floor The researchers found signals not only of the device had an intrinsic piezoelectric response
during storm events. The strongest micro- P-wave but also S-wave microseisms, both of around 5 pC/N. And it was able to harvest
seisms are generated by the interaction of in vertically (SV) and horizontally (SH) energy from various ambient motions, including
directly opposing wave systems. These cre- polarized forms. While modelling had body movements, machine and sound vibrations,
ate pressure excitations that travel almost only predicted the creation of SV waves, and wind flow.
unattenuated to the sea floor because of the researchers believe that the SH waves
When subjected to a repeated compressive
the nonlinear effects of the fluid – unlike may be generated by the repeated rever- stress of 0.17 MPa the nano-generator produced
with normal ocean surface waves, which beration of shear waves in poorly layered an output of 4 V with a current of 1.5 μA – or 6 μW
shallow sediments on the ocean floor of power. The researchers also linked four of the
decay with depth.
Microseisms – which are observed glob- (Science 10.1126/science.aaf7573).
devices together and were able to produce a
The discovery may offer a new way of voltage of 14 V. By gently slapping this device with
ally – may either travel across the surface
of the Earth, or through its interior as body understanding the nature of these cou- their hands, they were able to switch on more than
waves. Like the seismic waves generated by plings between the atmosphere and deep 50 light-emitting diodes. This shows that it is “a
earthquakes, these body waves may either Earth. The team is now developing new sustainable green power source”. The team now
be compressional (P-waves) or transverse methods to use body-wave microseisms to plan to scale up the nano-generator and “test it in
(S-waves). Until now, because of their larger explore the nature of the Earth’s interior different biomedical and self-powered devices”.
amplitude, only P-waves had been observed beneath oceanic storms.
Philae lander spotted on comet 67P at long last
Seismic ‘weather bomb’
P hy sic s Wor ld  Oc t ober 2016
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