Touch-Sensitive Artificial Skin For Robots

U.S. researchers said Sunday that new artificial “skin” fashioned out of flexible semiconductor materials can sense touch, making it possible for robots to be able to grip eggs but be strong enough to hold a frying pan as well.

Scientists have been struggling with a way to try and make robots be able to adjust the amount of force needed to hold different objects.  The pressure-sensitive materials are designed to help overcome that challenge.

Ali Javey, an electrical engineer at the University of California Berkeley, told The Associated Press (AP), “humans generally know how to hold a fragile egg without breaking it.”

“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 be able to grip a stock pot without dropping it,” Javey, who led one of two teams reporting on artificial skin discoveries in the journal Nature Materials, said in a statement.

The team found a way to make ultra tiny “nanowires” out of an alloy of silicon and germanium.  Materials from these wires were formed on the outside of a cylindrical drum depositing the wires in a uniform pattern.

A second team led by Zhenan Bao, a chemical engineer at Stanford University in California, made a material so sensitive it detects the weight of a butterfly resting on it.

Bao’s sensors were made by sandwiching a highly elastic rubber layer between two electrodes in a regular grid of tiny pyramids.

“We molded it into some kind of microstructure to incorporate some air pockets,” Bao said in a telephone interview with AP. “If we introduce air pockets, then these rubber pieces can bounce back.”

Once this material is stretched out, the artificial skin measures the change in electrical activity.

“The change in the thickness of the material is converted into an electrical signal,” she told AP.

The team hopes that artificial skin will eventually be used to restore the sense of touch in people who have prosthetic limbs.  However, scientists will first need to have a better understanding of how the system’s sensors work with the human nervous system.

The first team’s artificial skin is the latest application of new ways of processing brittle, inorganic semiconductor materials like silicon into flexible electronics.

A team at the California Institute of Technology in Pasadena devised a way earlier this year to help make flexible solar cells with silicon wires that are thin enough to be used in clothes.

Image 1: An optical image of a fully fabricated e-skin device with nanowire active matrix circuitry. Each dark square represents a single pixel. (Images: Ali Javey and Kuniharu Takei, UC Berkeley)

Image 2: An artist’s illustration of an artificial e-skin with nanowire active matrix circuitry covering a hand. The fragile egg illustrates the functionality of the e-skin device for prosthetic and robotic applications. (Images: Ali Javey and Kuniharu Takei, UC Berkeley)

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