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DISCOVERMAGAZINE.COM
THE TRIBOELECTRIC WAVE
Research on TriboElectric NanoGenerators (TENGs), which exploit
everyday static electricity to power devices, extends beyond the lab of
Zhong Lin Wang.
“A lot of research groups worldwide, from academics and industry, are
rushing to TENG research for self-powered internet-of-things sensors,
electronics and healthcare applications,” says electrical engineer Sang-
Woo Kim, a professor at South Korea’s Sungkyunkwan University.
In response to Wang’s initial research, Kim’s group was the next to
start pursuing TENGs. In 2015, they introduced a material that uses
triboelectric threads — clothing made from this material can charge a
smart watch after only a few hours of being worn. In 2017, they followed
up with a stretchable TENG-based fabric. The paper, published in
ACS Nano, discussed the relative power-generating merits of knitted
and woven textiles.
Ramakrishna Podila of Clemson University has been developing these
technologies for four years. He recently unveiled a TENG-based wireless
energy generation system
that uses PLA, a common
biodegradable polymer, as one
of its electrodes. In lab tests,
they found that it can charge
another device through the air
up to 16 feet away.
Micro-engineer Jürgen
Brugger’s group, in Switzerland,
has been developing hybrid
generators that combine
triboelectric and piezoelectric
materials. (Piezoelectric
materials generate current
when bent or deformed.) “If
one wants to get the maximum
energy out of any piece of a
device, one should combine
these different harvesting
mechanisms,” he says.
Nelson Sepúlveda at
Michigan State University
shares Wang’s vision of the
world as being rich with
wasted, harvestable energy. In
late 2016, he took the idea further by designing a FENG — a ferroelectret
nanogenerator. It works basically the same way as the TENG, except you
wouldn’t need to do anything to create a charge; the materials could
already have electric charges built in. When the charged materials press
together, the electric charges shift around, creating an imbalance, which
produces a current.
Sepúlveda’s group has used FENGs to create a Michigan State flag
that harvests energy by flapping in the wind — it can then double as
a loudspeaker that plays the school’s fight song. It could also work in
the other direction, as a microphone. Like Wang’s group, they’ve also
designed a keyboard that harvests the energy of keystrokes using
static electricity.
Nelson Sepúlveda wants to power the world
with FENGs — ferroelectret nanogenerators.