Tech Briefs Magazine - June 2021 - 48

Health & Biotech
Tiny Wireless Implant Detects Oxygen Deep Within the Body
The device, powered by ultrasound waves, could help doctors monitor the health of
transplanted organs and provide early warning of potential transplant failure.
University of California, Berkeley
ngineers have created a tiny wireless
implant that can provide realtime
measurements of tissue oxygen
levels deep underneath the skin. The
device, which is smaller than the average
ladybug and powered by ultrasound
waves, paves the way for the creation
of a variety of miniaturized sensors
that could track key biochemical
markers in the body such as pH or carbon
dioxide. These sensors could one
day provide doctors with minimally
invasive methods for monitoring the
biochemistry inside functioning organs
and tissues.
E
Oxygen is a key component to cells'
ability to harness energy from the food
that we eat and nearly all tissues in the
body require a steady supply in order
to survive. Most methods for measuring
tissue oxygenation can only provide
information about what is happening
near the surface of the body.
That is because these methods rely on
electromagnetic waves, such as infrared
light, which can only penetrate a few
centimeters into skin or organ tissue.
While there are types of magnetic resonance
imaging that can provide in -
formation about deep tissue oxygenation,
they require long scanning times
and so are unable to provide data in
real time.
Ultrasonic waves, which are a form of
sound too high in frequency to be
detected by the human ear, can travel
harmlessly through the body at much
longer distances than electromagnetic
waves and are already the basis of ultrasound
imaging technology in medicine.
Incorporating the oxygen sensor in -
volved integrating both an LED light
source and an optical detector into the
tiny device as well as designing a more
complicated set of electronic controls
to operate and read out the sensor.
This type of oxygen sensor differs from
the pulse oximeters that are used to
measure oxygen saturation in the
blood. While pulse oximeters measure
the proportion of hemoglobin in the
48
Cov
A schematic of the oxygen-detecting implant, which measures 4.5 by 3 millimeters. The μLED, O2sensing
film, and optical filter make up the oxygen sensor and are controlled by an integrated circuit
(IC). The piezocrystal converts an electronic signal from the IC into ultrasonic waves that can
be transmitted safely through living tissue. (UC Berkeley image: Soner Sonmezoglu)
The wireless implant can measure the oxygenation of living tissue deep below the surface of the
skin. (UC Berkeley photo: Soner Sonmezoglu)
blood that is oxygenated, the new device
is able to directly measure the amount of
oxygen in tissue.
One potential application of the
device is to monitor organ transplants
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ToC
because in the months after organ trans -
plantation, vascular complications can
occur and these complications may
lead to graft dysfunction. It could be
used to measure tumor hypoxia as well,
Tech Briefs, June 2021

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Tech Briefs Magazine - June 2021

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