Medical Design Briefs - September 2021 - 33

Soft Skin Patch Could Provide Early Warning for
Strokes, Heart Attacks
The patch uses ultrasound
to monitor blood flow to
organs.
UC San Diego
San Diego, CA
Engineers at the University of
California San Diego developed a soft
and stretchy ultrasound patch that can
be worn on the skin to monitor blood
flow through major arteries and veins
deep inside a person's body.
Knowing how fast and how much
blood flows through a patient's blood vessels
is important because it can help clinicians
diagnose various cardiovascular
conditions, including blood clots, heart
valve problems, poor circulation in the
limbs, or blockages in the arteries that
could lead to strokes or heart attacks.
The new ultrasound patch developed at
UC San Diego can continuously monitor
blood flow - as well as blood pressure and
heart function - in real time. Wearing
such a device could make it easier to identify
cardiovascular problems early on.
A team led by Sheng Xu, a professor
of nanoengineering at the UC San
Diego Jacobs School of Engineering,
reported the patch in a paper published
in Nature Biomedical Engineering.
The patch can be worn on the neck or
chest. What's special about the patch is
that it can sense and measure cardiovascular
signals as deep as 14 cm inside the
body in a noninvasive manner. And it
can do so with high accuracy.
" This type of wearable device can give you
a more comprehensive, more accurate picture
of what's going on in deep tissues and
critical organs like the heart and the brain,
all from the surface of the skin, " says Xu.
" Sensing signals at such depths is
extremely challenging for wearable electronics.
Yet, this is where the body's most
critical signals and the central organs are
buried, " says Chonghe Wang, a former
nanoengineering graduate student in
Xu's lab and co-first author of the study.
" We engineered a wearable device that
can penetrate such deep tissue depths
and sense those vital signals far beneath
the skin. This technology can provide
new insights for the field of healthcare. "
Another innovative feature of the
patch is that the ultrasound beam can be
tilted at different angles and steered to
Medical Design Briefs, September 2021
Intro
Cov
This soft, stretchy skin patch uses ultrasound to monitor blood flow to organs like the heart and
brain. (Credit: Nature Biomedical Engineering)
Ultrasound patch worn on the neck. (Credit: Nature Biomedical Engineering)
areas in the body that are not directly
underneath the patch.
This is a first in the field of wearables,
explains Xu, because existing wearable
sensors typically only monitor areas right
below them. " If you want to sense signals
at a different position, you have to move
the sensor to that location. With this
patch, we can probe areas that are wider
than the device's footprint. This can
open up a lot of opportunities. "
■ How It Works
The patch is made up of a thin sheet
of flexible, stretchable polymer that
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adheres to the skin. Embedded on the
patch is an array of millimeter-sized
ultrasound transducers. Each is individually
controlled by a computer - this
type of array is known as an ultrasound
phased array. It is a key part of the technology
because it gives the patch the
ability to go deeper and wider.
The phased array offers two main
modes of operation. In one mode, all
the transducers can be synchronized to
transmit ultrasound waves together,
which produces a high-intensity ultrasound
beam that focuses on one spot as
deep as 14 cm in the body. In the other
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Medical Design Briefs - September 2021

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