Artificial Skin Materials with a Sense of Touch

Technology Review - Published By MIT

Electric Skin that Rivals the Real Thing

The tactile sensitivity of human skin is hard to re-create, especially over large, flexible surfaces. But two California research groups have made pressure-sensing devices that significantly advance the state of the art.

 One, made by researchers at Stanford University, is based on organic electronics and is 1,000 times more sensitive than human skin. The second, made by researchers at the University of California, Berkeley, uses integrated arrays of nanowire transistors and requires very little power. Both devices are flexible and can be printed over large areas; they are described this week in separate papers in the journal Nature Materials.

Stanford researchers' new high-sensitivity electronic skin can feel a butterfly's footsteps

Stanford researchers have developed an ultrasensitive, highly flexible, electronic sensor that can feel a touch as light as an alighting fly.  Manufactured in large sheets, the sensors could be used in artificial electronic skin for prosthetic limbs, robots, touch-screen displays, automobile safety and a range of medical applications.
By sandwiching a precisely molded, highly elastic rubber layer between two parallel electrodes, the team created an electronic sensor that can detect the slightest touch.

"It detects pressures well below the pressure exerted by a 20 milligram bluebottle fly carcass we experimented with, and does so with unprecedented speed," said Zhenan Bao, an associate professor of chemical engineering who led the research.
The key innovation in the new sensor is the use of a thin film of rubber molded into a grid of tiny pyramids, Bao said. She is the senior author of a paper published Sept.  12 online by Nature Materials.
The sensor is sensitive enough to detect this horinea faunus butterfly placed on it.

Engineers make artificial skin out of nanowires

Engineers at UC Berkeley have developed a pressure-sensitive electronic material from semiconductor nanowires that could one day give new meaning to the term "thin-skinned."

"The idea is to have a material that functions like the human skin, which means incorporating the ability to feel and touch objects," said Ali Javey, associate professor of electrical engineering and computer sciences and head of the UC Berkeley research team developing the artificial skin.

The artificial skin, dubbed "e-skin" by the UC Berkeley researchers, is described in a Sept. 12 paper in the advanced online publication of the journal Nature Materials. It is the first such material made out of inorganic single crystalline semiconductors.

A touch-sensitive artificial skin would help overcome a key challenge in robotics: adapting the amount of force needed to hold and manipulate a wide range of objects.

"Humans generally know how to hold a fragile egg without breaking it," said Javey, who is also a member of the Berkeley Sensor and Actuator Center and a faculty scientist at the Lawrence Berkeley National Laboratory Materials Sciences Division. "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."

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.