"Super skin" is what Stanford researcher Zhenan Bao wants to create. She's already developed a flexible sensor that is so sensitive to pressure it can feel a fly touch down. Now she's working to add the ability to detect chemicals and sense various kinds of biological molecules.
She's also making the skin self-powering, using polymer solar cells to generate electricity. And the new solar cells are not just flexible, but stretchable, they can be stretched up to 30 percent beyond their original length and snap back without any damage or loss of power. "With artificial skin, we can basically incorporate any function we desire," said Bao, a professor of chemical engineering.
"That is why I call our skin 'super skin.' It is much more than what we think of as normal skin." The foundation for the artificial skin is a flexible organic 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 only needs to be a nanometre or two thick. "Depending on what kind of material we put on the sensors and how we modify the semiconducting material in the transistor, we can adjust the sensors to sense chemicals or biological material," she said.
The foundation for the artificial skin is a flexible organic transistor, made with flexible polymers and carbon-based materials. Photos by L.A. Cicero.
Bao's team has successfully demonstrated the concept by detecting a certain kind of DNA. The researchers are now