LOS ANGELES—Self-healing shoes, toys and potentially even tires are within reach, thanks to 3D-printed polymers developed by researchers at the University of Southern California Viterbi School of Engineering.
Polymers that heal themselves through the application of heat can be manufactured using a 3D printing method that uses photopolymerization, according to Quiming Wang, assistant professor at USC-Viterbi, and colleagues Kunhao Yu, An Xin, Haixu Du and Ying Li.
The scientists published their research Feb. 1 in NPG Asia Materials, according to USC-Viterbi.
"Nature excels in both self-healing and 3D shaping," the abstract to the paper said. "For example, self-healable human organs feature functional geometries and microstructures.
"However, tailoring man-made self-healing materials into complex structures faces substantial challenges."
The paradigm for manufacturing self-healing elastomers, the abstract said, relies on a molecularly designed photoelastomer ink with both thiol and disulfide groups.
"The former facilitates a thiol-ene photopolymerization during the additive manufacturing process, and the latter enables a disulfide metathesis reaction during the self-healing process," it said. "We find that the competition between the thiol and disulfide groups governs the photocuring rate and self-healing efficiency of the photoelastomer."
The result is a 3D-printed material creating new functions for a wide range of purposes, from flexible electronics to sound control, according to USC-Viterbi. A 17.5-millimeter square can be printed out in just five seconds, completing whole objects in about 20 minutes, it said.
The researchers demonstrated the material's usefulness on a range of products including shoe pads, soft robots, multiphase composites and electronic sensors, the college said.
The self-healing elastomer works as a do-it-yourself technology, according to Wang.
"If you just put a broken shoe on a bench at room temperature, the rubber will heal itself in six to eight hours," he said. "If you apply heat, at maybe 60°C, that accelerates the healing process to about two hours."
Wang said he already has been approached by several shoe companies interested in the self-healing technology. He declined to name them.
While self-healing tires are a possibility, they will take more research to become a reality, according to Wang. Because tires are tough and complex, the photoelastomer would have to be stronger than it currently is, he said.
"How would that work?" Wang said. "We would have to include nanoparticles." No tire makers have contacted USC-Viterbi to date, he said.