IEEE Spectrum November, 2014 - 63

multiple biomarkers might allow physicians to conduct cardiac stress tests on a
treadmill without drawing blood. They
could also measure the impact of drugs
on the body so that dosages could be
determined more precisely, as opposed
to the crude estimates we use now based
merely on age and body weight.
There is still work to do on the digital
signal processing and algorithms needed
to analyze the raw electrical measurements of biomarkers in sweat. But a
physical-exertion sensor patch is a near
reality, about to be tried on hundreds
of people. If all goes well, we could have
sweat-sensing patches-at least sensors
for athletics-on the market in low volUltimately, sweat-sensing patches ume next year. These do not have to go
will measure multiple electrolytes, through a lengthy approval process with
metabolites, and other biomarkers at the the U.S. Food and Drug Administration
same time. Their designers will no doubt because they are not meant to be used for
have to devise some clever algorithms to diagnosis or treatment of disease.
The second-generation patch we're
account for differences in the way various electrolytes, metabolites, and bio- now working on in the lab is nearly
It includes
markersSBIR-STTR-big-idea-shadow-ad-final.pdf
migrate into sweat. But it will be complete.
1
8/7/14
1:52 PM secure Bluetooth
worth the effort. Being able to measure communication, data storage, and a

Orexin-A, a neuropeptide biomarker
that measures alertness.
In an attempt to push the limits of
detection of biomarkers even further,
investigators at the Air Force Research
Laboratory led by Rajesh Naik are coating nanowires, nanotubes, and graphene electrodes as part of a field-effect
transistor with biorecognition elements.
These researchers have already built
sensors capable of measuring biomarkers present at only a 1/100-picomolar
concentration in simulated sweat. The
issue here, for now, is that nanowires
and graphene are still a bit exotic and
not yet easily manufacturable.

small microcontroller to detect higherfrequency and more complex signals
from the electronic sensors on the patch.
Analysis of these more sophisticated
waveforms is critical for the detection of
the really low-concentration biomarkers,
like cytokines. Ultimately, sweat analysis will offer minute-by-minute insight
into what is happening in the body, with
on-demand sampling in a manner that
is convenient and unobtrusive.
Researchers have understood the richness of the information carried in sweat
for some 50 years, but they have been
unable to take advantage of it because
of the difficulty of collecting, transporting, and analyzing the samples. With
the many recent advances in sensing,
computing, and wearable technology
providing inspiration-and with more
than a little perspiration in the laboratory-we are on the verge of a true revolution in wearable diagnostics. n
PoSt YoUr CoMMEntS at http://spectrum.
ieee.org/sweat1114

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Table of Contents for the Digital Edition of IEEE Spectrum November, 2014