Interview - Joseph Smith on Applying Flexible Flat Panel Display Technology to Wearable Biomedical Devices

Full text

1298 ELECTRONICS LETTERS 20th August 2015 Vol.51 No.17
that the PPG signal is
strongest directly over
(small) arteries or veins.
Research revealed that
position dependence is one
of the key issues limiting the
widespread adoption of PPG
measurements in determining more
clinically-useful physiological parameters,
such as detecting arrhythmia. Because of the
inability to optimally position the location of the
PPG sensor, today’s wearables appear to be good
for just taking your pulse and not much else. We
believe that a more useful sensor would instead
use a much larger 2D OLED and photodiode sen-
sor array manufactured on a fl exible substrate
that can instead position at least one of the sen-
sors in the array directly over an artery or vein to
lock in and maximise the detected PPG signal.
Could this approach be used for other
applications?
For biomedical diagnostic applications, the
use of display technology provides a sensing
area that is orders of magnitude larger and less
expensive than conventional CMOS or discrete
component-based biosensors. This allows for
easier integration with area intensive chemical
and biological recognition material and enables
a larger number of unique recognition sites on
each device for multiple disease and pathogen
detection.
We’re also looking at integrating our OLED
display and photodiode sensor array technolo-
gy with programmable fl uorescent microarray
biorecognition technology to fabricate dispos-
able point-of-care immunosensors. We’ve also
explored a disposable OLED-based optoge-
netic nerve stimulator to treat mental health
disorders and infl ammatory diseases.
How do you think this technology will
develop over the next decade?
Over the next 10 years, we envision that giv-
en adequate investment, a sizeable portion of
today’s medical diagnostic instrumentation can
transition into cheap and disposable confi gura-
tions that will eventually become as ubiquitous
and as widely used as the box of Band-Aids®
found in most home medicine cabinets. Essen-
tially, we would like to see point-of-care and
wearable biomedical device technology start
advancing at the same rapid pace as today’s
smart phone and mobile technology. Hopefully,
by combining what is arguably the most impor-
tant component in smart phones – the colour
display – with medical diagnostic technology,
we can help accelerate our vision.
Dr Joseph Smith from
Arizona State Univer-
sity, in the USA, on the
work behind the paper
‘Application of Flexible
Flat Panel Display Technol-
ogy to Wearable Biomedical
Devices’, page 1312.
How did you come to work in this area?
We’ve been investigating whether the same
commercial fl at panel display technology used in
mobile devices, PCs, and HDTVs can also be
applied to manufacture low cost and ideally dis-
posable biomedical sensors. On a per unit area
basis, fl at panel displays are an amazingly inex-
pensive high tech product, that cost only a few
cents per cm2 to manufacture, and continue to get
even cheaper. This seemed to us like a huge
untapped and relatively unexplored opportunity,
especially for the fast growing wearables market.
As for my involvement, I took a graduate
biosensors class about two years ago, which
started the fl ex-bio program at Arizona State
University, and it’s continued to take off.
What led you to investigate display tech-
nology for biomedical sensing?
Actually, it’s pretty simple. I’m a research
engineer at the Flexible Electronics and Dis-
play Center at Arizona State University, and
my initial focus was developing fl exible organ-
ic light emitting diode – OLED display and
fl exible digital x-ray detector technology. It
was a natural transition to also look at applying
the same technology that I was working on to
biomedical sensing.
What have you reported in your paper?
We explored how the same commercial fl at
panel technology used in the production of our
fl exible OLED displays and digital x-ray
detectors, can also be applied to reduce the
manufacturing cost of wearable biomedical
devices, as well as potentially improve their
diagnostic functionality. A prototype photople-
thysmograph (PPG) sensor for optical heart
rate monitoring using fl exible green OLED
display and fl exible a-Si PIN photodiode sen-
sor technology was developed and then used as
a test case to illustrate our new approach.
How is this approach signifi cant?
Initially we were thinking that our approach
was primarily a new technique to reduce manu-
facturing costs. However, we observed that the
intensity of the detected PPG signal was strongly
position dependent, which is not surprising given
interview
“The use of display technology provides a sensing area orders
ofmagnitude larger and less expensive than conventional CMOS
or discrete component-based biosensors”
Joseph Smith
R
po
of t
h
w
id
es
p
m
easurem
e
al
doi: 10.1049/el.2015.2700