CU Boulder researchers have developed a new type of malleable, self-healing, and fully recyclable “electronic skin” that has applications ranging from robotics and prosthetic development to better biomedical devices.
Electronic skin, known as e-skin, is a thin, translucent material that can mimic the function and mechanical properties of human skin. A number of different types and sizes of wearable e-skins are now being developed in labs around the world as researchers recognize their value in diverse medical, scientific, and engineering fields.
The new CU Boulder e-skin has sensors embedded to measure pressure, temperature, humidity, and air flow, said Jianliang Xiao, an assistant professor in CU Boulder’s Department of Mechanical Engineering who is leading the research effort with Wei Zhang, an associate professor in CU Boulder’s Department of Chemistry and Biochemistry as well as a faculty member in the Materials Science and Engineering Program.
The technology has several distinctive properties, including a novel type of covalently bonded dynamic network polymer, known as polyimine that has been laced with silver nanoparticles to provide better mechanical strength, chemical stability and electrical conductivity.
A paper on the subject was published in the journal Science Advances. Co-authors on the study include Zhanan Zou and Yan Li of mechanical engineering and Chengpu Zhu and Xingfeng Lei of chemistry and biochemistry. The study was funded, in part, by the National Science Foundation.
Many people are familiar with the movie The Terminator, in which the skin of film’s main villain is “re-healed” just seconds after being shot, beaten or run over, said Zhang. While the new process is not nearly as dramatic, the healing of cut or broken e-skin, including the sensors, is done by using a mix of three commercially available compounds in ethanol, he said.
Another benefit of the new CU Boulder e-skin is that it 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.
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.