Tuesday, 23 July 2013

Paper-thin e-skin responds to touch by lighting up

Paper-thin e-skin responds to
touch by lighting up
Shown is a fully fabricated 16x16
pixel e-skin that lights up when
touched. Credit: Photo by Ali Javey
and Chuan Wang
A new milestone by engineers at the
University of California, Berkeley, can
help robots become more touchy-
feely, literally.
A research team led by Ali Javey, UC
Berkeley associate professor of
electrical engineering and computer
sciences, has created the first user-
interactive sensor network on flexible
plastic. The new electronic skin, or e-
skin, responds to touch by instantly
lighting up. The more intense the
pressure, the brighter the light it
emits.
"We are not just making devices; we
are building systems," said Javey,
who also has an appointment as a
faculty scientist at the Lawrence
Berkeley National Laboratory. "With
the interactive e-skin, we have
demonstrated an elegant system on
plastic that can be wrapped around
different objects to enable a new
form of human-machine interfacing."
This latest e-skin, described in a
paper to be published online this
Sunday, July 21, in the journal Nature
Materials, builds on Javey's earlier
work using semiconductor nanowire
transistors layered on top of thin
rubber sheets.
In addition to giving robots a finer
sense of touch , the engineers believe
the new e-skin technology could also
be used to create things like
wallpapers that double as
touchscreen displays and dashboard
laminates that allow drivers to adjust
electronic controls with the wave of a
hand.
In this artistic illustration of an
interactive e-skin, organic LEDs are
turned on locally where the surface
is touched. The intensity of the
emitted light quantifies the
magnitude of the applied pressure.
Credit: Illustration by Ali Javey and
Chuan Wang
"I could also imagine an e-skin
bandage applied to an arm as a
health monitor that continuously
checks blood pressure and pulse
rates," said study co-lead author
Chuan Wang, who conducted the
work as a post-doctoral researcher in
Javey's lab at UC Berkeley.
The experimental samples of the
latest e-skin measure 16-by-16
pixels. Within each pixel sits a
transistor, an organic LED and a
pressure sensor.
"Integrating sensors into a network is
not new, but converting the data
obtained into something interactive is
the breakthrough," said Wang, who is
now an assistant professor of
electrical and computer engineering
at Michigan State University. "And
unlike the stiff touchscreens on
iPhones, computer monitors and
ATMs, the e-skin is flexible and can
be easily laminated on any surface."
To create the pliable e-skin, the
engineers cured a thin layer of
polymer on top of a silicon wafer.
Once the plastic hardened, they
could run the material through
fabrication tools already in use in the
semiconductor industry to layer on
the electronic components. After the
electronics were stacked, they simply
peeled off the plastic from the silicon
base, leaving a freestanding film with
a sensor network embedded in it.
"The electronic components are all
vertically integrated, which is a fairly
sophisticated system to put onto a
relatively cheap piece of plastic," said
Javey. "What makes this technology
potentially easy to commercialize is
that the process meshes well with
existing semiconductor machinery."
Javey's lab is now in the process of
engineering the e-skin sensors to
respond to temperature and light as
well as pressure.
More information: Nature Materials
DOI 10.1038/nmat3711

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