NEWS & TECHNOLOGY FLEXIBLE ELECTRONICS
Stretchable skin-like robot crawls and convey objects
CBy Julien happich ombining simple elastomeric electroactuators and
electroadhesives, researchers at the Bristol Robotics
Laboratory have designed a fully stretchable and rollable
skin-like robot that crawl and convey small objects across a
surface.
Schematic diagram of the ElectroSkin
design showing regions powered for
electroadhesion and actuation.
A fully soft ElectroSkin robot stretching
in hand. Scale bars is 1 cm.
In a paper titled “All-Soft Skin-Like Structures for Robotic
Locomotion and Transportation” published in the journal of
Soft Robotics, the researchers led by Professor of Robotics
Jonathan Rossiter developed what they describe as ElectroSkin
robots, consisting of dielectric elastomer actuators (DEAs) and
soft electroadhesives (EAs) in a fully compliant multilayer composite
skin-like structure.
The dielectric elastomer actuators were simply made of
deformable dielectric membranes sandwiched between two
compliant electrodes (made of conductive silicone), in effect,
forming soft and variable parallel capacitors that can be deformed
under the application of an electric field due to Maxwell
pressure.
The soft-stretchable electroadhesives consist of compliant
planar electrodes embedded in a soft dielectric, they behave
like variable coplanar capacitors which produce controllable adhesion
(as electrostiction) under a voltage. Applying an electric
field between the electrodes causes polarization in any object in
direct contact and induces electrostatic attraction forces.
The paper describes how through a careful timing of electroactivation,
the actuation of the DEA pairs and the adhesion and
release cycles of the EA pairs can be sequenced into a gripmove
release-relax cycle that will incrementally
move the soft robot skin across a surface or
alternatively, acting as a thin conveyor belt,
move an object across its surface. More simply
explained, moving in a fashion similar to soft
organisms like snails and slugs, the soft robot
crawls across the surface by alternately contracting
its artificial muscles and gripping the
surface using electrical charges.
To prove the concept, the authors designed
a soft self-actuating conveyor belt
able to transport small objects at a speed of
0.28 mm/s. Since the active areas can be exploited as electromechanical
actuators or as electrostatic gripper elements,
or both simultaneously, the ElectroSkin robot can be driven in
many different modes and future optimized designs could enable
such robots to crawl up walls and across ceiling, explore
difficult to reach environments including collapsed buildings.
The researchers also demonstrated an untethered
ElectroSkin conveyor, based on a miniature microprocessor,
a Li-Po battery, and two small and lightweight high-voltage
amplifiers. Next they plan to integrate stretchable triboelectric
nanogenerators to aim for self-powered ElectroSkin robots.
“ElectroSkin is an important step toward soft robots that can
be easily transported, deployed and even worn. The combination
of electrical artificial muscles and electrical gripping
replicated the movements of animals like slugs and snails, and
where they can go, so could our robots!”, commented Professor
Rossiter.
1mm-thick solid-state batteries beat all performance benchmarks
By Julien Happich
Researchers from CEA-Leti have designed all-solid,
inorganic thin-film batteries (TFBs) that exhibit better
performance than prior art devices and could expand
the market for tiny energy-storage units in medical implantable,
injectable and wearable solutions.
Presented at IEDM 2019 in a paper titled
“Millimeter Scale Thin-Film Batteries for Integrated
High-Energy-Density Storage”, the
new design boasts an areal energy density
of 890 μAh.cm-2, the highest reported so far
for such devices, according to the authors.
The new TFB architecture also exhibits high
power density, reaching capacity as high
as 450 μAh.cm-2 under 3mA.cm-2 current
density.
“Thin-film batteries provide some of
the highest energy densities of electrochemical energy storage
devices, but the inability to increase the electrodes’ thicknesses
and control the geometry on the micrometer scale has thus far
hindered their effective areal energy density and integration in
miniaturized devices”, explained the authors.
The team’s solution to these challenges is a high-energydensity,
millimeter-scale, thin-film battery integrating a 20μmthick
LiCoO2 cathode in a Li-free anode configuration, built on
silicon wafers using UV photolithography and etching for the
successive deposition and patterning
of each layer. Because it is built using
a wafer-level process, the new battery
could be tightly integrated with other
electronic devices such as implantables,
cutting on assembly costs and increasing
reliability.
“Implantable sensors or biologicalfunction
monitoring systems such as
intra-ocular pressure sensors and bloodglucose
measurement would be particularly
SEM cross-sectional characterizations of
the sub-100μm-thick TFB structure.
suited for our TFBs,” observed Sami Oukassi, lead author
of the paper. “External systems, such as cochlear implants and
smart contact lenses would also benefit from the advantages of
this breakthrough.”
22 News January 2020 @eeNewsEurope www.eenewseurope.com
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