Medical Design Briefs - November 2021 - 36

tion that has published research on
comb breathalyzers, Ye says.
Breath analysis is the leading medical
application for frequency combs. Combs
offer a combination of broad spectral
coverage, high resolution, and high sensitivity,
potentially
detecting tens of
chemicals simultaneously. Among other
advantages, the comb system would not
require chemical reagents and complex
laboratory facilities.
Ye and Nesbitt are now working with
other NIST researchers to engineer a
compact version of the breathalyzer. The
Licking a Tootsie Roll®
The candy was used as
an electrode to detect
salt and electrolyte levels
in saliva.
ACS
Washington, DC
Single-use diagnostic tests often aren't
practical for health professionals or pa -
tients in resource-limited areas, where
cost and waste disposal are big concerns.
So, researchers reporting in ACS Applied
Materials & Interfaces have turned to a surprising
material, Tootsie Roll® candy, to
develop an inexpensive and low-waste
device. The candy was used as an electrode,
the part of the sensor that detects
salt and electrolyte levels in saliva, to monitor
ovulation status or kidney health.
Disposable test strips have advanced
the speed and accuracy of at-home
health monitoring. For example, ovulation
predictor kits measure luteinizing
hormone levels, and there are test strips
that measure creatinine levels for
patients with chronic kidney disease.
However, their costs add up quickly and,
between the packaging and the strips
themselves, there's a lot of waste that
needs to be disposed of.
Previous researchers have indicated
that simple measurements of a person's
tube is only 55 cm (21.7 in.) long, but
the laser comb is custom-made and
somewhat bulky.
The work is funded by the Air Force
Office of Scientific Research, the
National Science Foundation, and NIST.
For more information, visit www.nist.gov.
Sensor to Monitor Health
An electrode made with a molded Tootsie Roll® and
aluminum tubes can help monitor ovulation status
and kidney health. (Credit: Adapted from ACS
Applied Materials & Interfaces 2021, DOI:
10.1021/acsami.1c11306)
salivary salt and electrolyte content could
be appropriate for managing some conditions.
So, Beelee Chua and Donghyun
Lee wanted to repurpose unconventional
and widely available materials, including
electrically conductive soft candies,
into an easily accessible, low-waste sensor
that could simply be licked by patients to
analyze their saliva.
To make the prototype sensor, the
researchers first flattened a Tootsie Roll
and pressed crevices into its surface in a
crosshatched pattern to hold the saliva
sample. Then, they inserted two thin,
reusable aluminum tubes, which
acted as electrical contacts, connecting
the candy electrode into a circuit
with a current source and an output
voltage detector. In preliminary tests,
the device could measure salt levels
that were physiologically relevant for
health monitoring in a salt-water solution
and artificial saliva.
For example, when covered in
diluted artificial saliva, the sensor
could reliably measure a change in
voltage low enough to detect the 10-
30 percent drop in salts that occurs
when a person ovulates. While the
maximum salt content in the artificial
saliva samples was similar to that of a
healthy adult, the researchers used
calculations to estimate that conductivities
three times higher, which signal a
problem with the kidneys, would be within
the measurable range of the device.
Although testing with real human
samples is still needed, the researchers
say that using soft candy as electrodes
opens up the possibility for low-waste,
inexpensive electrochemical sensors and
circuits in the future.
The authors acknowledge funding
from the National Research Foundation
of Korea.
For more information, visit www.acs.org.
Wearable Brain-Machine Interface Turns Intentions
into Actions
The system could improve
the quality of life for
people with motor
dysfunction or paralysis.
Georgia Tech
Atlanta, Georgia
A new wearable brain-machine interface
(BMI) system could improve the
36
Cov
quality of life for people with motor dysfunction
or paralysis, even those struggling
with locked-in syndrome - when a
person is fully conscious but unable to
move or communicate.
A multi-institutional, international
team of researchers led by the lab of
Woon-Hong
Yeo at the Georgia
Institute of Technology combined
wireless soft scalp electronics and virwww.medicaldesignbriefs.com
ToC
tual
reality in a BMI system that allows
the user to imagine an action and wirelessly
control a wheelchair or robotic
arm.
The team, which included researchers
from the University of Kent (United
Kingdom) and Yonsei University (Re -
public of Korea), describes the new
motor imagery-based BMI system in the
journal Advanced Science.
Medical Design Briefs, November 2021
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Medical Design Briefs - November 2021

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