The nature magazine Nature Materials reported
on the efforts of two independent US research groups had developed an
artificial, electronic skin that has the ability to sense, and respond
to, a very light touch. This “e-skin” is made of semiconductor
nanowires that operate using very low voltage. It is the first such
material made out of inorganic single crystalline semiconductors. The
skin can be applied by rubbing it or rolling it onto a surface and can
detect pressure around 0 to 15 kilopascals, which would allow a robot
helper, for instance, to do the dishes or handle a pet without causing
damage.
"If we ever wanted a robot that could unload the dishes, for instance,
we'd want to make sure it doesn't break the wine glasses in the
process. But we'd also want the robot to grip the stock pot without
dropping it,” Ali Javey, an associate professor of computer sciences at
the University of California at Berkeley, who led the research teams,
said. "The idea is to have a material that functions like the human
skin, which means incorporating the ability to feel and touch objects."
She said a longer term goal would be to use the e-skin to restore the
sense of touch to patients with prosthetic limbs, which would require
significant advances in the integration of electronic sensors with the
human nervous system: Previous attempts to develop an artificial skin
relied upon organic materials because they are flexible and easier to
process. "The problem is that organic materials are poor
semiconductors, which means electronic devices made out of them would
often require high voltages to operate the circuitry," said Javey.
"Inorganic materials, such as crystalline silicon, on the other hand,
have excellent electrical properties and can operate on low power.”
Research member and co-author Kuniharu Takei wrote in Nature Materials
that large-scale integration of high-performance electronic components
on mechanically flexible substrates might also enable new applications
in electronics, sensing and energy. He also noted that contact printing
of parallel arrays of semiconductor nanowires (NWs) has been explored
as a versatile route to enable fabrication of high-performance,
bendable transistors and sensors.
“The development of an electronic skin is critical to the realization
of artificial intelligence that comes into direct contact with humans,
and to biomedical applications such as prosthetic skin. To mimic the
tactile sensing properties of natural skin, large arrays of pixel
pressure sensors on a flexible and stretchable substrate are required,”
an excerpt from the article explained. “We demonstrate flexible,
capacitive pressure sensors with unprecedented sensitivity and very
short response times that can be inexpensively fabricated over large
areas by microstructuring of thin films of the biocompatible elastomer
polydimethylsiloxane.”
An article summary explained the pressure sensitivity of the
microstructured films far surpassed that exhibited by unstructured
elastomeric films of similar thickness, and is tunable by using
different microstructures. “The microstructured films were integrated
into organic field-effect transistors as the dielectric layer, forming
a new type of active sensor device with similarly excellent sensitivity
and response times,” the article reported.
John J. Boland, who is at the School of Chemistry and the CRANN
Nanoscience Institute in Trinity College in Dublin, said thanks to
flexible electronics, the world is within touch of skin. Flexible
arrays of transducers can now be fabricated with pressure sensitivity
and response times approaching those of natural human skin, he said.
“As humans, we interact with our immediate environment through our
senses — sight, sound, smell, taste and touch,” he said. “Emulation of
the senses by electronic means has long been a grand challenge of
artificial intelligence and is pivotal in the development of accessible
and natural interfaces between man and machine.”
Midmarket News & Reviews 
