Electronic skin, or e-skin, is a thin, translucent material that is designed to mimic the function and properties of human skin. Those researching e-skin believe it could one day be used for robotics, better and more lifelike prosthetics, or even usher in a new age of biomedical devices.
Yet, getting the e-skin to actually stretch to conform to the shape of the body and maintain function is a challenge as is the longevity of these devices, as they can’t withstand the same amount of use or abuse of human skin.
However that may be changing with a new development by the University of Colorado at Boulder in a new type of self-healing, flexible and fully recyclable electronic skin. This skin has sensors embedded to measure pressure, temperature, humidity and air flow.
Researchers made the e-skin with several distinctive properties including a type of covalently bonded dynamic network polymer, called polyimine, which is laced with silver nanoparticles to provide better mechanical strength, chemical stability and electrical conductivity.
“What is unique here is that the chemical bonding of polyimine we use allows the e-skin to be both self-healing and fully recyclable at room temperature,” says Jianliang Xiao, assistant professor at CU Boulder’s Department of Mechanical Engineering. “Given the millions of tons of electronic waste generated worldwide every year, the recyclability of our e-skin makes good economic and environmental sense.”
Researchers say the self-healing of a cut or broken e-skin, including the sensors, is done by using a mix of three commercially available compounds in ethanol. The e-skin can also conform to curved surfaces, such as human arms or robotic hands, by applying moderate heat and pressure to it without introducing excessive stresses.
“Let’s say you wanted a robot to take care of a baby,” says Wei Zhang, an associate professor in CU Boulder's Materials Science and Engineering Program. “In that case you would integrate e-skin on the robot fingers that can feel the pressure of the baby. The idea is to try and mimic biological skin with e-skin that has desired functions.”
The e-skin is recycled by soaking it in a recycling solution where the polymers degrade into oligomers and monomers that are soluble in ethanol. The silver nanoparticles then sink to the bottom of the solution. The recycled solution and nanoparticles can then be used to make a new, functional e-skin.