Stretchy Solar Cells Power Up Artificial 'Super Skin'
|The foundation for artificial|
Our skin is exquisitely sensitive and pliable good qualities to look for when designing materials that can wrap around objects and act as sensors.
Researchers at Stanford University have made strides with an artificial skin. The plastic-like material they have dubbed "super skin" is sensitive enough to feel the pressure of a fly touching down, and it uses flexible, stretchable solar cells to power itself. These cells can be stretched 30 percent beyond their original length and snap back without any damage or loss of power.
Now the scientists are working to make their material detect chemicals and sense various kinds of biological molecules.
"With artificial skin, we can basically incorporate any function we desire," said Zhenan Bao, a Stanford professor of chemical engineering who co-authored a study appearing in an upcoming issue of Advanced Materials. "That is why I call our skin 'super skin.' It is much more than what we think of as normal skin."
As described in a Stanford news release, the foundation for the artificial skin is a transistor made with flexible polymers and carbon-based materials. To allow touch sensing, the transistor contains a thin, highly elastic rubber layer molded into a grid of tiny inverted pyramids. When pressed, this layer changes thickness, which changes the current flow through the transistor. The sensors have from several hundred thousand to 25 million pyramids per square centimeter, corresponding to the desired level of sensitivity.
To sense a particular biological molecule, the surface of the transistor has to be coated with another molecule to which the first one will bind when it comes into contact. The coating layer needs to be only a nanometer (a billionth of a meter) or two thick.
Bao's team has used super skin to detect a certain kind of DNA. The researchers are now working on extending the technique to detect proteins, which could prove useful for medical diagnostics.
"For any particular disease, there are usually one or more specific proteins associated with it called biomarkers that are akin to a smoking gun, and detecting those protein biomarkers will allow us to diagnose the disease," Bao said.
The same approach would allow the sensors to detect chemicals, she said. By adjusting aspects of the transistor structure, the super skin can detect chemical substances in either vapor or liquid environments.
Bao, who presented her work Feb. 20 in Washington at the annual American Association for the Advancement of Science meeting, said she sees super skin as much more than mimicry of human skin; it could allow robots or other devices to perform functions beyond that of our biological outer coatings.
"You can imagine a robot hand that can be used to touch some liquid and detect certain markers or a certain protein that is associated with some kind of disease and the robot will be able to effectively say, 'Oh, this person has that disease,'" she said. "Or the robot might touch the sweat from somebody and be able to say, 'Oh, this person is drunk.'"