Scientists have developed a new type of malleable, self-healing and fully recyclable “electronic skin” that can be used in biomedical devices like artificial limbs and prosthetics. The new e-skin has sensors embedded to measure pressure, temperature, humidity and air flow. It also has several distinctive properties, including a novel type of covalently bonded dynamic network polymer, known as polyimine. The polyimine has been 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,” said Jianliang Xiao, Assistant Professor at the University of Colorado – Boulder.
“Given the millions of tons of electronic waste generated worldwide every year, the recyclability of our e-skin makes good economic and environmental sense,” Xiao added. The e-skin, detailed in the journal Science Advances, can be easily conformed to curved surfaces like human arms and 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. In that case you would integrate e-skin on the robot fingers that can feel the pressure of the baby,” explained Wei Zhang, Associate Professor from the varsity. “The idea is to try and mimic biological skin with e-skin that has desired functions,” he said.
To recycle the skin, the device is soaked into recycling solution, making the polymers degrade into oligomers (polymers with polymerization degree usually below 10) and monomers (small molecules that can be joined together into polymers) that are soluble in ethanol. The silver nanoparticles sink to the bottom of the solution. “The recycled solution and nanoparticles can then be used to make new, functional e-skin,” Xiao said.