“Superskin” goes solar

A new ultrasensitive electronic skin can detect chemicals and biological molecules in addition to sensing an incredibly light touch. And now, this “superskin” can be powered by stretchable solar cells, opening up more applications in clothing, robots, prosthetic limbs and more.

Researchers at Stanford University are making the skin self-powering, using polymer cells to generate electricity. The new cells are not just flexible but also stretchable. They can be stretched up to 30 percent beyond their original length and snap back without any damage or loss of power.

The artificial skin’s foundation is a flexible organic transistor made with 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 its thickness, altering the current flow through the transistor. The sensors have from several hundred thousand to 25 million pyramids per square centimeter, depending upon the desired level of sensitivity.

The foundation for the artificial skin is an organic transistor made with flexible polymers and carbon-based materials. Courtesy of L.A. Cicero.

To detect a particular biological molecule, the surface of the transistor must be coated with a different molecule that binds to the first one when both come into contact. The coating layer has to be only 1 or 2 nm thick. The sensor can be adjusted to detect chemical or biological materials.

The team members successfully demonstrated the concept by detecting a certain kind of DNA. They are now working to extend the technique to detect specific protein biomarkers that could be useful for medical diagnostics. The same approach can also be used to detect chemical substances in either vapor or liquid environments, they said.

Regardless of what the sensors detect, they transmit their data to the processing center, whether a human brain or a computer, via electronic signals. Running on solar power, the sensors are light, mobile and simple to use.

The discovery has opened the door to many possible applications. Its stretchability offers the potential to bond solar cells to curved surfaces such as car exteriors or architectural elements without cracking or wrinkling. One day, the innovation could even allow robots and other devices to perform functions that human skin cannot.

The research appeared online Feb. 25, 2011, in Advanced Materials (doi: 10.1002/adma.201004426).