Self-repairing 3D-printed rubber material developed
Image credit: Mkcs | Dreamstime.com
Researchers at the University of Southern California Viterbi School of Engineering have developed a 3D-printed rubber materials that can self-repair.
Working with Viterbi students Kunhao Yu, An Xin and Haixu Du, and University of Connecticut’s assistant professor Ying Li, the faculty’s assistant professor Qiming Wang have made a new material that can be manufactured quickly and is able to repair itself if it becomes fractured or punctured.
It is hoped that this material could be a game-changer for industries such as shoes, tires, soft robotics and electronics sectors, decreasing manufacturing time while increasing product durability and longevity.
The material was manufactured using a 3D printing method that uses photopolymerisation, which uses light to solidify a liquid resin into a desired shape or geometry.
Photopolymerisation is achieved through a reaction with a certain chemical group called thiols. By adding an oxidiser to the equation, thiols transform into another group called disulphides. It is the disulphide group that can reform when broken, leading to the self-healing ability.
“When we gradually increase the oxidant, the self-healing behaviour becomes stronger, but the photopolymerisation behaviour becomes weaker,” explained Wang. “There is competition between these two behaviours. Eventually we found the ratio that can enable both high self-healing and relatively rapid photopolymerisation.”
When doing tests using photopolymerisation, in five seconds the scientists were able to print a 17.5mm square, completing whole objects in around 20 minutes that can repair in just a few hours. Furthermore, they demonstrated the material’s ability on a range of products, including a shoe pad, a soft robot (as shown below), a multiphase composite and an electronic sensor.
After the products were cut in half, within two hours (four hours for the electronics, due to the carbon used to transmit electricity) at a temperature of 60°C the subjects had self-repaired, retaining their strength and function. Furthermore, the researchers found the repair time can be decreased by raising the temperature.
“We actually show that under different temperatures – from 40°C to 60°C – the material can heal to almost 100 per cent,” said structural engineering student, Yu. “By changing the temperature, we can manipulate the healing speed. Even under room temperature the material can still self-heal.”
The team are now working to develop different self-healable materials along a range of stiffnesses, from the current soft rubber, to rigid hard-plastics. Such materials could be used for vehicle parts, composite materials and body armour.
At the start of February 2019, scientists from the University of California Berkeley (UCB) developed a new type of 3D print that uses light to transform liquids into complex solid objects in a matter of minutes.