Last September we covered a story about a pressure-sensitive artificial skin developed at Stanford University that is so sensitive it can “feel” the weight of a butterfly.
As part of a goal to create what she calls “super skin,” Stanford researcher Zhenan Bao is now giving the artificial skin the ability to detect chemical and biological molecules. Not only that, she has also developed a new, stretchable solar cell that can be used to power the skin, opening up the possibility of an artificial skin for robots that can be used to power them and enable them to detect dangerous chemicals or diagnose medical conditions with a touch.
The touch-sensitive flexible organic transistor previously developed by the Stanford researchers forms the foundation of the new artificial skin. It consists of a highly elastic rubber layer that is molded onto a matrix of microscopic inverted pyramids. This rubber film is sandwiched between two parallel electrodes, which register compressions and rebounds as electrical signals of various strengths.
By altering the shape and density of the pyramids, the sensitivity of the material can be tweaked to more closely mimic the different sensitivities of skin on different parts of the body. Existing samples range from several hundred thousand to 25 million pyramids per square centimeter, corresponding to the desired level of sensitivity. Bao has also replaced some of the materials in earlier versions of the transistor with biodegradable materials so it is now more eco-friendly.
Chemical and biological molecule detection
To enhance the skin and give it the ability to sense a particular biological or chemical molecule, it needs to be coated with another molecule that will bind with the biological or chemical molecules when they come in contact.
“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,” Bao said.