Tech Briefs Magazine - April 2022 - 36

Sensors
Previous work involved using nanomaterials
for sensing because their large
surface-to-volume ratio makes them
highly sensitive; however, the nanomaterial
is not something that can receive a
signal, necessitating the need for interdigitated
electrodes, which are like the
fingers on a hand.
The researchers used a laser to pattern a
highly porous single line of nanomaterial
similar to graphene for sensors that detect
gas, biomolecules, and in the future, chemicals.
In the nonsensing portion of the device
platform, the team created a series of
serpentine lines coated with silver. When
an electrical current is applied to the silver,
the gas sensing region locally heats up due
to significantly larger electrical resistance,
eliminating the need for a separate heater.
The serpentine lines allow the device to
stretch, like springs, to adjust to the flexing
of the body for wearable sensors.
The nanomaterials used in this work
are reduced graphene oxide and molybdenum
disulfide or a combination of the
two, or a metal oxide composite consisting
of a core of zinc oxide and a shell of copper
oxide, representing the two classes of
widely used gas sensor materials - low-dimensional
and metal oxide nanomaterials.
Using a CO2
laser, multiple sensors
can be made on the platform. The plan
is to have tens to a hundred sensors, each
selective to a different molecule like an
electronic nose, to decode multiple components
in a complex mixture.
Applications include a wearable sensor
to detect chemical and biological
agents that could damage the nerves or
lungs, and patient health monitoring
including gaseous biomarker detection
from the human body and environmental
detection of pollutants that can affect
the lungs.
The sensor can detect nitrogen dioxide,
which is produced by vehicle emissions,
and sulfur dioxide, which, together with
nitrogen dioxide, causes acid rain. These
gases can be an issue in industrial safety.
The researchers' next step is to create
high-density arrays, improve the signal,
and make the sensors more selective.
This may involve using machine learning
to identify the distinct signals of individual
molecules on the platform.
For more information, contact Walt Mills
at wem12@psu.edu; 814-865-0285.
Miniaturized, Wireless Oxygen Sensor for Sick Infants
The mobile, wearable device could allow babies to leave the hospital and be monitored
from home.
Worcester Polytechnic Institute, Worcester, MA
A
sensor the size of a Band-Aid can
measure a baby's blood oxygen levels,
a vital indication of the lungs' effectiveness
and whether the baby's tissue is
receiving adequate oxygen supply. Unlike
current systems used in hospitals,
this miniaturized wearable device is flexible
and stretchable, wireless, inexpensive,
and mobile - possibly allowing the
child to leave the hospital and be monitored
remotely.
Typically, measuring oxygen molecule
levels transcutaneously involves using a
system with an approximately 5-pound
monitor plugged into an electrical outlet
and sensors that generally are wired to
the monitor. The new device uses wireless
power transfer and is connected to
the internet wirelessly so an alarm on
a monitor in a doctor's office or smartphone
app would notify medical personnel
and family members if the baby's
oxygen level begins to drop.
The device is designed to measure PO2
,
or the partial pressure of oxygen - which
indicates the amount of oxygen dissolved
in the blood - a more accurate indicator
of respiratory health than a simple
oxygen saturation measurement, which
can be easily taken with a pulse oximetry
device gently clamped on a finger. And
measuring the PO2
level via a noninvasive
device attached on the skin is as accurate
as a blood test. The wearable baby oxygen
36
An early prototype of the miniaturized, wearable device that will one day monitor infants' blood oxygen
levels. (Photo: Worcester Polytechnic Institute)
monitor also would be useful for adults,
especially people with severe asthma and
seniors with Chronic Obstructive Pulmonary
Disease (COPD), which is an incurable,
progressive lung disease.
A chip would act as the heart for the
wearable device. The chip, designed to
work inside the wearable oxygen monitor,
activates the optical sensors, captures analog
signals from the sensor, handles power
management, and contains required
circuitry. The individual circuits, such as
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signal capturing circuits and driver circuits
for optical based read-out circuits,
were custom designed. In the next phase
of the research project, the chip will be
equipped with more circuitries to digitize
the analog signals, transmit the captured
and digitized data, and create power from
a wireless link. At that point, it will be a
complete system on the chip.
For more information, contact Colleen
Bamford Wamback at cbwamback@wpi.edu;
508-831-6775.
Tech Briefs, April 2022
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Tech Briefs Magazine - April 2022

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