Medical Design Briefs - November 2021 - 31

Woven Nanotube Fibers Turn Heat into Power
Flexible thermoelectric
generators could be a
useful way to make
carbon 'green.'
Rice University
Houston, TX
Invisibly small carbon nanotubes
aligned as fibers and sewn into fabrics
become a thermoelectric generator that
can turn heat from the sun or other
sources into energy.
The Rice University lab of physicist
Junichiro Kono led an effort with scientists
at Tokyo Metropolitan University
and the Rice-based Carbon Hub to make
custom nanotube fibers and test their
potential for large-scale applications.
Their small-scale experiments led to a
fiber-enhanced, flexible cotton fabric
that turned heat into enough energy to
power an LED. With further development,
they say such materials could
become building blocks for fiber and
textile electronics and energy harvesting.
The same nanotube fibers could also
be used as heat sinks to actively cool sensitive
electronics with high efficiency. A
paper about the project appears in
Nature Communications.
The effect seems simple: If one side of
a thermoelectric material is hotter than
the other, it produces energy. The heat
can come from the sun or other devices
like the hotplates used in the fabric
experiment. Conversely, adding energy
can prompt the material to cool the hotter
side.
Until now, no macroscopic assemblies
of nanomaterials have displayed the necessary
" giant power factor, " about 14
mW per meter kelvin squared, that the
Rice researchers measured in carbon
nanotube fibers.
" The power factor tells you how much
power density you can get out of a material
upon certain temperature difference
and temperature gradient, "
says Rice
graduate student Natsumi Komatsu, lead
author of the paper. She noted a material's
power factor is a combined effect
from its electrical conductivity and what's
known as the Seebeck coefficient, a
measure of its ability to translate thermal
differences into electricity.
" The ultrahigh electrical conductivity
of this fiber was one of the key attributes, "
Komatsu says.
Medical Design Briefs, November 2021
Cov
Carbon nanotubes woven into thread-like fibers and sewn into fabrics become a thermoelectric generator
that can turn heat from the sun or other sources into energy in a project developed at Rice
University. (Credit: Jeff Fitlow/Rice University)
The source of this superpower also
relates to tuning the nanotubes' inherent
Fermi energy, a property that determines
electrochemical potential. The
researchers were able to control the
Fermi energy by chemically doping the
nanotubes made into fibers by the Rice
lab of co-author and chemical and biowww.medicaldesignbriefs.com
ToC
molecular
engineer Matteo Pasquali,
allowing them to tune the fibers' electronic
properties.
While the fibers they tested were cut
into centimeter lengths, Komatsu says
there's no reason devices can't make use
of the excellent nanotube fibers from
the Pasquali lab that are spooled in con31
Rice
University graduate student Natsumi Komatsu shows a carbon nanotube fiber-enhanced, flexible
cotton fabric that turns heat into enough energy to power an LED. Such thermoelectric generators
can turn heat from the sun or other sources into energy. (Credit: Jeff Fitlow/Rice University)

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Medical Design Briefs - November 2021

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