Signal Processing - November 2016 - 11

effective way of monitoring personal
health. Continuously sampling human
sweat, which is rich in physiological
information, promises a convenient,
informative, and noninvasive monitoring mechanism.
Existing noninvasive sweat biosensors either monitor only a single
molecule at a time or lack the signal
processing necessary to compensate
Flexible Sensor Array
for temperature effects or interactions
among different molecules. But a new
wearable monitoring device, developed
by University of California, Berkeley,
researchers, promises to give its wearers a
Smart Wristband
fully integrated "perspiration analysis system" (Figure 3). Working with counterparts at the Stanford University School of
Wireless Flexible PCB
Medicine, the researchers developed
a monitor that binds to the skin and
measures certain sweat metabolites
Figure 3. A new wearable monitoring device, developed by the University of California, Berkeley,
and electrolytes. The device can
researchers, promises to give its wearers a fully integrated "perspiration analysis system."
also calibrate its readings based on
(Image courtesy of University of California, Berkeley.)
skin temperature.
Sweat secretion is a complex prothe accurate reading of the sensors,"
(Na and K ions), and skin temperature,"
cess, notes project researcher Wei Gao, a
he explains.
Gao says.
Berkeley postdoctoral fellow. "Our plat"By properly choosing different
According to Gao, the measureform is a powerful tool that can signifitypes of signal processing and introducment of Na and K levels is facilicantly advance large-scale and real-time
ing real-time system calibration, such
tated through the use of ion selective
physiological and clinical studies by
as temperature compensation, our deelectrodes. The potential output of
facilitating the identification of informavice can provide very stable readings,"
these sensors is linearly related to
tive biomarkers in sweat," he says. Data
Gao says. "In addition, the independent
the logarithm of the
read by the device
and selective operation of individual
concentration of
can be used to alert
the new technology
sensors is preserved by electrically detar get electrolytes.
wearers and caregiveffectively spans the
coupling the operating points of each
The resistance-based
ers to specific health
gap between signal
sensor's interface."
temperature sensor
concerns, such as
Gao says that the project's next step
is
based
on
metallic
dehydration, fatigue,
transduction, signal
is
performing
population-level studies.
microwires;
higher
and dangerously high
processing, and wireless
"Sweat contains physiologically rich intemperatures result
body temperatures.
transmission in wearable
formation about what's happening in the
in higher resistance.
Gao feels that the
biosensors by merging
body, with many different substances,
"Our device can
new technology efplastic-based skin sensors real-time measure the from electrolyte ions and metabolites
fectively spans the
with silicon-integrated
to protein molecules," Gao notes. "The
electrical signals gengap between signal
same platform can be exploited or reerated
from
all
the
transduction, sigcircuits consolidated
configured for in-situ analyses of other
sensors,"
Gao
says.
nal processing, and
onto a flexible circuit
biomarkers within sweat and other huThe device meawireless transmission
board for complex
man fluid samples to facilitate personsures the electrical
in wearable biosensignal processing.
alized and real-time physiological and
signals generated
sors by merging plasclinical investigations."
by all of the sensors
tic-based skin sensors
simultaneously. "Signal processing is
with silicon-integrated circuits consoliimportant to average the data and filter
dated onto a flexible circuit board for
Author
out noise and interference in the meacomplex signal processing. "Our device
John Edwards (jedwards@john
surements," Gao says. "More imporcontains five sensors that can measure
edwardsmedia.com) is a technology writer
tantly, it allows us to do the real-time
simultaneously the sweat metabobased in the Phoenix, Arizona, area.
sp
compensation and calibration to ensure
lites (glucose and lactate), electrolytes
IEEE Signal Processing Magazine

November 2016

http://www.edwardsmedia.com

Table of Contents for the Digital Edition of Signal Processing - November 2016