SKIN LIKE DEVICE MONITORS CARDIOVASCULAR AND SKIN HEALTH
A new wearable medical
device can quickly alert a person if they are having cardiovascular trouble or
if it's simply time to put on some skin moisturizer, reports a Northwestern
University and University of Illinois at Urbana-Champaign study
The small device,
approximately five centimeters square, can be placed directly on the skin and
worn 24/7 for around-the-clock health monitoring. The wireless technology uses
thousands of tiny liquid crystals on a flexible substrate to sense heat. When
the device turns color, the wearer knows something is awry.
"Our device is
mechanically invisible -- it is ultrathin and comfortable -- much like skin
itself," said Northwestern's Yonggang Huang, one of the senior
researchers. The research team tested the device on people's wrists.
"One can imagine
cosmetics companies being interested in the ability to measure skin's dryness
in a portable and non-intrusive way," Huang said. "This is the first
device of its kind."
Huang led the portion
of the research focused on theory, design and modeling. He is the Joseph
Cummings Professor of Civil and Environmental Engineering and Mechanical
Engineering at Northwestern's McCormick School of Engineering and Applied Science.
The technology and its
relevance to basic medicine have been demonstrated in this study, although
additional testing is needed before the device can be put to use. Details are
reported online in the journal Nature Communications.
"The device is
very practical -- when your skin is stretched, compressed or twisted, the
device stretches, compresses or twists right along with it," said Yihui
Zhang, co-first author of the study and research assistant professor of civil
and environmental engineering at Northwestern.
The technology uses
the transient temperature change at the skin's surface to determine blood flow
rate, which is of direct relevance to cardiovascular health, and skin hydration
levels. (When skin is dehydrated, the thermal conductivity property changes.)
The device is an array
of up to 3,600 liquid crystals, each half a millimeter square, laid out on a
thin, soft and stretchable substrate.
When a crystal senses
temperature, it changes color, Huang said, and the dense array provides a
snapshot of how the temperature is distributed across the area of the device.
An algorithm translates the temperature data into an accurate health report,
all in less than 30 seconds.
"These results
provide the first examples of 'epidermal' photonic sensors," said John A.
Rogers, the paper's corresponding author and a Swanlund Chair and professor of
materials science and engineering at the University of Illinois. "This
technology significantly expands the range of functionality in skin-mounted
devices beyond that possible with electronics alone."
Rogers, who also is
director of the Seitz Materials Research Laboratory, led the group that worked
on the experimental and fabrication work of the device. He is a longtime
collaborator of Huang's.
With its 3,600 liquid
crystals, the photonic device has 3,600 temperature points, providing
sub-millimeter spatial resolution that is comparable to the infrared technology
currently used in hospitals.
The infrared
technology, however, is expensive and limited to clinical and laboratory
settings, while the new device offers low cost and portability.
The device also has a
wireless heating system that can be powered by electromagnetic waves present in
the air. The heating system is used to determine the thermal properties of the
skin.
The National Science
Foundation supported the research.
The title of the paper
is "Epidermal Photonic Devices for Quantitative Imaging of Temperature and
Thermal Transport Characteristics of the Skin." In addition to Zhang, Li
Gao and Viktor Malyarchuk of the University of Illinois at Urbana-Champaign are
co-first authors.
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