With near-total sustainability now a major goal of many corporations, the creation of self-healing rubber could help them achieve this.
In the near future, a broken shoe may not mean that you immediately throw it in the bin – rather, you just wait a while for it to fix itself. That’s the amazing breakthrough achieved by a team of engineers in the US that has developed 3D-printed rubber material with self-healing properties.
Publishing its findings in NPG Asia Materials, the team from the University of Southern California Viterbi School of Engineering said these new materials can be manufactured quickly and could be game-changing for industries such as shoes, tires, soft robotics and even electronics, thereby decreasing manufacturing time while increasing product durability and longevity.
The material is created using a 3D-printing method known as photopolymerisation, whereby light is used to solidify a liquid resin to form a desired shape or geometry. However, in order to make it self-heal, the team had to alter it at the atomic level.
Photopolymerisation is achieved through a reaction with a certain chemical group called thiols. When an oxidiser is added into the equation, thiols transform into another group called disulphides. It is this group that is able to reform when broken – by finding the right ratio between thiols and disulphides, the amazing property is achieved.
Heals at room temperature
“There is competition between these two behaviours and eventually we found the ratio that can enable both high self-healing and relatively rapid photopolymerisation,” explained Qiming Wang of the research team.
In as little as five seconds, the team can print a 17.5mm square, with whole objects being created in around 20 minutes. Once damaged, the object can repair itself in just a few hours. This was demonstrated on a range of products, including a shoe pad, a soft robot, a multiphase composite and an electronic sensor.
During testing, an object was cut in half and then put back together in a room with a temperature of 60 degrees Celsius. After just two hours, the team demonstrated that the object had fused again and was functional as a flexible device.
Kunhao Yu, first author of the study, said this temperature allows for almost 100pc healing in the objects, but even at room temperature the material can still self-heal.
Now, the team’s focus is to develop self-healing materials in regular rubber and hard plastics, potentially allowing for their use in vehicle parts and body armour.