Tech Briefs Magazine - May 2024 - 27

Sensor Measures Light, Heat, and Touch
Inspired by the behavior of natural skin, the sensor measures changes in body temperature
and reacts to both sunlight and warm touch.
Linköping University, Sweden
R
obotics, prostheses that react to touch,
and health monitoring are three fields
in which scientists are working to develop
electronic skin. Re searchers have developed
a sensor that, similar to human
skin, can sense temperature variation
that originates from the touch of a warm
object as well as the heat from solar radiation.
The sensor combines pyroelectric
and thermoelectric effects with a nano-optical
phenomenon.
A voltage arises in pyroelectric materials
when they are heated or cooled. It is
the change in temperature that gives a
signal, which is rapid and strong, but
that decays almost as rapidly. In thermoelectric
materials, in contrast, a voltage
arises when the material has one cold
and one hot side. The signal here arises
slowly and some time must pass before it
can be measured. The heat may arise
from a warm touch or from the Sun; all
that is required is that one side is colder
than the other.
A pyroelectric polymer was combined
with a thermoelectric gel, resulting in a
rapid and strong signal that lasts as long as
the stimulus is present. Furthermore, the
two materials interact in a way that reinforces
the signal.
The sensor also uses another nano-optical
entity known as plasmons, which
The sensor combines pyroelectric and thermoelectric effects with a nano-optical phenomenon.
(Image: Thor Balkhed)
arise when light interacts with nanoparticles
of metals such as gold and silver.
The incident light causes the electrons
in the particles to oscillate in unison,
which forms the plasmon. This phenomenon
provides the nanostructures with
optical properties such as high scattering
and high absorption.
The sensor is also pressure-sensitive so a
signal arises when the sensor is pressed
with a finger, but not when it is subjected it
to the same pressure with a piece of plastic
- it reacts to the heat of the hand.
For more information, contact Magnus
Jonsson at magnus.jonsson@liu.se; +46
11-36-34-03.
New Patch Can Help Control Robotic Exoskeletons
The patch, about the size of a BandAid, sticks to your skin and picks up tiny signals coming
from human muscles.
University of Colorado Boulder, CO
I
n a new study, engineers from Korea and
the United States have developed a wearable,
stretchy patch that could help to
bridge the divide between people and machines
- and with benefits for the health
of humans around the world.
The patch, about the size of a BandAid,
sticks to your skin and picks up tiny signals
coming from human muscles. In lab experiments,
the researchers showed that humans
could use these devices to operate
robotic exoskeletons more efficiently.
" We get these natural signals from
muscles and send them to outside equipTech
Briefs, May 2024
ment to give people more control, " said
study co-lead and Associate Professor Jianliang
Xiao.
The team described its design, known as
the stretchable microneedle adhesive patch
(SNAP), in the journal Science Advances.
The secret to SNAP comes down to
what the researchers call " microneedles. "
The patches are integrated with
an array of about 144 needles. They are
made of silicon coated with gold and
are less than a hundredth of an inch
long, making them hard to see with the
naked eye.
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The idea of small needles poking your
body may sound scary, but the team's microneedles
only enter the top layer of
your skin and aren't long enough to
reach the body's pain sensors. That
makes the patches surprisingly comfortable
to wear, even for long periods.
" People can wear these patches for a
week, and we see hardly any skin irritation, "
said study co-lead Jae-Woong Jeong said.
Xiao noted that the human body, just
like many machines, is pulsing with electricity
on a near constant basis. Every time
you bend your arm, twist your back, or even
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Tech Briefs Magazine - May 2024

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