A newly developed 3D printed rubber materials can repair themselves, an advance that could bring transformation in the manufacturing of tires, shoes, and soft robotics, according to a study published in NPG Asia Materials.
Developed by a team of researchers at the University of Connecticut and University of Southern California Viterbi School of Engineering (USC Viterbi), the new material is described to have the advantage of being quick to produce as well as improving durability and longevity of products.
To develop the new flexible 3D printed rubber materials, the researcher used a 3D printing technique based on photopolymerization. It is a process of solidifying a liquid resin by using light, which is achieved through a reaction with a type of organosulfur compounds called ‘thiols’ that can be converted into disulfides with the addition of an oxidizer. The disulfide group can reform when broken, resulting into an ability to heal itself. Identifying the ideal ratio between these two chemical groups was key to revealing the excellent properties of the material.
Qiming Wang, Assistant Professor at USC Viterbi, said that gradually increasing the oxidant strengthened the self-healing behavior but weakened the photopolymerization behavior.
In search of ways to break the competition between these two behaviors, the researchers found the ratio that will allow high self-healing as well as relatively fast photopolymerization.
A 17.5mm square of the material can be printed in just five seconds and complete the entire object in nearly 20 minutes that are capable of repairing themselves in a few hours. The team demonstrated the ability of the material on a variety of products including electronic sensor, a multiphase composite, a soft robot, and a shoe pad.
When these items are cut in half, they could heal completely and recover their function and strength in just two hours. For an electronic component, the process extended to four hours, while the researchers said the repair time can be reduced by increasing the temperature.
Under varying temperatures from 40-60 degree Celsius, the new material can heal to almost 100%. According to the researchers, the healing speed can be manipulated by changing the temperature and the material can heal to an extent even under the room temperature.