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Could nanowire skin help robots do the dishes?

UC Berkeley engineers have developed a low-power e-skin of touch-sensitive nanowire mesh that may help robots manipulate fragile objects.

Next-gen tattoo: The nanowire skin sports a polymer-based mold in the shape of a C for "Cal."
Next-gen tattoo: The nanowire skin sports a polymer-based mold in the shape of a C for "Cal." Ali Javey and Kuniharu Takei, UC Berkeley

The dream of having a robot do the dishes may get a step closer with a touch-sensitive electronic skin made of flexible sensors, according to engineers at University of California at Berkeley. And presumably, it wouldn't get dishpan hands.

In a letter published by Nature Materials, the researchers describe a low-power but robust material that would have some of the properties of human skin, such as the ability to feel and touch. Such artificial skin might also help restore limb feeling to amputees.

The e-skin is based on inorganic single crystalline semiconductors. The engineers including Ali Javey and Kuniharu Takei grew germanium/silicon nanowires on a cylinder and then rolled them onto a polyimide film substrate, depositing the wires in a pattern.

An artist's conception of an e-skin glove holding an egg.
Light touch: An artist's conception of an e-skin glove holding an egg. Ali Javey and Kuniharu Takei

The result was a shiny, thin, and flexible electronic material organized into a matrix of transistors, each of which with hundreds of semiconductor nanowires.

A pressure-sensitive rubber was added to the surface of the matrix for sensing. It has the ability to detect pressure from 0 to 15 kilopascals, equivalent to the force needed to grasp light objects. A robot with e-skin hands could handle wine glasses without breaking them.

To show how it can detect pressure, a rubber mold in the shape of the letter C (for "Cal") was placed over the matrix, and about 15 kilopascals of pressure was applied. As seen in the study, the matrix pixels imaged the pressure profile into a blurry but recognizable C.

E-skin for robot applications is under development by other groups, including an MIT-Peratech partnership working on spiky metallic nanoparticles. DARPA, which helped sponsor the Berkeley research, has a Revolutionizing Prosthetics program that is investigating the creation of synthetic skin to improve artificial limbs.

The Berkeley skin matrix is about 19 inches square, a significant size achievement for ordered nanowire circuitry, according to the study. It works on less than 5 volts and can continue operating after more than 2,000 bending cycles, demonstrating its flexibility.

"The limit now to the size of the e-skin we developed is the size of the processing tools we are using," Takei was quoted as saying in a UC Berkeley release.

That'll be perfect for those big-boned robot servants we'll all have in the future. All they'll need is some Palmolive for softer manipulators.