Robot Revolution: New Material Sensitive as Human Skin

Anne Minard
for National Geographic News
June 8, 2006
It's hundreds of times thinner than a human hair but as sensitive as a human finger.

Researchers have devised a "nanosheet" that can be wrapped around any surface—such as that of a surgical instrument or a robotic hand—to mimic the sensitivity of touch.

(Related: "Fake Skin Gives Robots Sense of Touch" [August 17, 2005].)

The sensitive sheet was produced by encouraging microscopic particles to bond to the sensor surface by dipping the materials in a series of chemical baths.

The resulting material is only about a hundred nanometers, or a hundred-billionths of a meter, thick. (Video: Nanotechnology: The New Plastic.)

The nanosheet is essentially an electric sandwich of metal layers and semiconducting particles.

When something touches it, the pressure changes the current in the sheet, and the affected particles in the sheet light up.

In a demonstration, this light pattern was captured by a miniscule camera, which transmitted the image to a viewing screen.

Vivek Maheshwari, at the University of Nebraska in Lincoln, and Ravi Saraf, at the Virginia College of Osteopathic Medicine in Blacksburg, led the research. Their work will appear in tomorrow's issue of the journal Science.

Touching Without Touching

Saraf says the new sensor technology overcomes two long-standing hurdles: It drastically refines the scale of sensitivity from the range of about two millimeters to the resolution of human touch. And it's a flexible sheet, so it avoids the old clumsiness of trying to fit more rigid material to a complex surface, like that of a robot's "finger."

"It's almost like a paint," he said. "You can deposit this on any surface you like."

The sensor can detect differences in hardness, so it has the potential to detect cancer and gallstones. That ability could add a critical component to today's minimally invasive surgeries, Saraf says.

"If you have an endoscope—a fiber optic cable [that transmits images from the insides of organs]—the surgeon sees the optical image," he said.

But doctors often can't detect, say, tumors and gallstones through sight alone. The new supersensitive sensors could "feel" a patient's insides and transmit the impression as a visual image.

Saraf is working on a project now whereby a doctor could press the sensor onto tissue suspected to contain cancer cells and tell exactly where those cancer cells are. Such precision could reduce the amount of tissue removed in, for example, breast cancer surgery.

"Moreover," the researchers point out in the paper, "there is great interest in developing humanoid robots that can sense shapes, textures, and hardness and manipulate complex objects, [tasks] which are not readily possible by vision alone."

Saraf said the new technology is reasonably cheap, costing 50 cents to a dollar (U.S.) per square inch to produce. It can be made in sheets of up to a meter, or about three feet, square.


Lukas Lichtensteiger is a postdoctoral fellow at Harvard University's Department of Chemistry and Chemical Biology in Cambridge, Massachusetts.

He works on self-assembling micro-robotic systems, which involve components that come together without human interference.

In nature, this type of activity occurs when proteins form and when DNA replicates. In the lab similar processes can be used to create materials that heal themselves when heated, among other feats.

Lichtensteiger called the work by Maheshwari and Saraf "a very elegant new approach."

"I expect that we will soon see self-assembling nanostructures as integral parts in many other robotic sensors and actuators," he said.

In a related Perspectives piece in the same issue of Science, engineer Richard Crowder of the United Kingdom's University of Southampton agrees that the new sensor shows great promise for medicine and robotics.

"However, as with most sensors of this resolution and size, the challenge is to extract the sensor's information efficiently—something the nervous system does with supreme efficiency," he wrote, adding that repeated trials will reveal the accuracy of the new sensor.

Study co-author Saraf said the next direction he wants to go in is temperature imaging.

"If I could image temperature at the same resolution, I could build infrared cameras a hundred times better than we have today," he said. He adds that this could improve technologies such as night vision and cameras on space telescopes.

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