Medical Design Briefs - October 2022 - 43

wearer to pick up a 10-lb object. Testing
the apparel on a mannequin showed it
could do so without an assist from human
muscles.
" Census statistics say there are about
25 million adults in the United States
who find it difficult to lift 10 lbs with
their arms, " says Rajappan, a postdoc
supported by the Rice Academy of Fellows.
" That's something we commonly
do in our daily lives, picking up household
objects or even a baby. "
The system requires two components:
textile pumps embedded in the soles of
walking shoes that harvest air pressure
and pneumatic actuators that make use
of that pressure where needed. The
pumps are filled with open-cell polyurethane
foam that allows them to recover
their shape after every footfall.
Preston says the pump is small
enough to be comfortable. " The stiffness
of the foam is about on par with a
typical shoe insert, " he says. " We wanted
to make sure this felt like something
you'd actually want to have inside of
your shoe. "
Tests by the Rice lab showed the devices
produce the equivalent of 3 W of power
with a conversion efficiency of more
than 20 percent, easily outperforming
electromagnetic, piezoelectric and triboelectric
strategies for foot-strike energy
harvesting, including one designed by
students at Rice's Oshman Engineering
Design Kitchen.
Preston says that all the components
for a single device cost the lab about $20.
He says that the products were simple
to assemble and yet robust enough to
be cleaned in a washing
machine with no
degradation in device
performance.
Energy storage
bladder (ESB)
" The fabrication approach
uses techniques
that are already employed
in the garment
industry, things like
cutting textile sheets
and bonding them
with heat and pressure, "
he says. 'We're
ready to think about
translating our work
towards products. "
Rajappan says that
along with test
units,
the lab also developed
mathematical models
to predict how well an
assistive device would
perform based on a user's
weight and walking
speed, among other
parameters. " One way
to take this forward will
be to use the model
to optimize performance
for specific
user groups, " he says.
" We're also think20
cm
Energy harvesting
device (EHD)
2 cm
The Preston lab made its lightweight, machine-washable energy harvesting
devices tough enough for everyday use. (Credit: Preston Innovation Lab)
ing about devices like pneumatic actuators
that apply therapeutic compression
for things like deep vein thrombosis,
blood clots in the legs, " Rajappan says.
" Anything that requires air pressure can
be powered by our system. "
" Now that we're providing the power,
we can tap into all the existing work on
actuation, " Preston adds. " This would include
things like gloves that help people
close their hands, assistance at both the
elbow and shoulder joints, and other devices
that still rely on typically rigid and
bulky power supplies that are either uncomfortable
or require being tethered
to external infrastructure. "
He notes conversations with fashion
consultants could be in his future, to
keep wearers from resembling the Michelin
Man.
" We've managed to keep it quite low
profile, but yes, that's definitely something
to think about, especially with the
actuators, " Preston says.
Co-authors are graduate students Te
Anoop Rajappan, left, and Daniel Preston of Rice University set up an experiment with their fabric air
pump. The lab developed its textile-based energy harvesting shoe able to power assistive devices for
people with disabilities. (Credit: Brandon Martin)
Medical Design Briefs, October 2022
www.medicaldesignbriefs.com
Faye Yap, Zhen Liu, Marquise Bell, and
Barclay Jumet of Rice and Vanessa Sanchez
of Harvard University. The National
Science Foundation (2144809, 1842494)
supported the research.
This article was written by Mike Williams,
Rich University. For more information,
visit https://news.rice.edu. Contact:
mikewilliams@rice.edu. A video of the
technology is available at https://youtu.
be/t5QSM3pHB-k.
43

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Medical Design Briefs - October 2022

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