Researchers from the University of Southern California have 3D-printed a self-healing rubber material for car tires and shoes. By using photopolymerization, the researchers printed objects of numerous shapes and sizes.
For the material to heal itself, the scientists dug deeper into the chemistry behind it. To create the self-healing process, the USC researchers added an oxidizer to the mix, transforming the material into a new chemical group known as disulfides which have healing abilities.
“When we gradually increase the oxidant, the self-healing behavior becomes stronger, but the photopolymerization behavior becomes weaker,” Qiming Wang lead author of the study, said. “There is competition between these two behaviors. Eventually, we found the ratio that can enable both high self-healing and relatively rapid photopolymerization.”
The Self-Healing Rubber
The researchers can print a 17.5-millimeter square of the material in just 5 seconds. On average, they can 3D-print a self-healing material or object in around 20 minutes. The material itself can heal in just a few hours.
In their study, published in the journal NPG Asia Materials, the researchers demonstrated the ability of their material in a variety of products like a soft robot, shoe pad, electronic sensor, and a multiphase composite.
They cut each of the products in half then left them to heal. In just two hours, the objects healed completely and retained their strength and function.
“We actually show that under different temperatures — from 40 degrees Celsius to 60 degrees Celsius — the material can heal to almost 100 percent,” Kunhao Yu, a student at the University of Southern California Viterbi School of Engineering, explained. “By changing the temperature, we can manipulate the healing speed, even under room temperature the material can still self-heal.”
The team is now working on developing other self-healing materials that are stronger and more rigid like hard plastics.
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