Shining a light on UNSW’s self-healing 3D printed plastic

3D printed plastic

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Research by UNSW academics shows that special treatment of liquid resin used in 3D printing can cause the material to mend itself if it becomes damaged. 

UNSW engineers have demonstrated a way to help 3D printed plastic heal itself at room temperature using only lights. 

Professor Cyrille Boyer and his team, Dr Nathaniel Corrigan and Michael Zhang from the UNSW School of Chemical Engineering realised that adding a “special powder” to the liquid resin used in the printing process can later assist to ensure quick and easy repairs if the material breaks. 

This is done simply by shining standard LED lights on the printed plastic for around one hour, causing a chemical reaction and fusion of the two broken pieces.  

The entire process makes the repaired plastic stronger than before it was damaged. It is hoped that further development and commercialisation of the technique will help to reduce chemical waste in the future. Broken plastic parts would not need to be discarded or recycled and could be easily mended even while embedded in a component among many other materials. 

The results of the team’s research have now been published in the journal, Angewandte Chemie International Edition. 

“In many places where you use a polymer material, you can use this technology. So, if a component fails, you can repair the material without having to throw it away,” Corrigan said. 

“There is an obvious environmental benefit because you’re not having to re-synthesize a brand-new material every time it gets broken. We are increasing the lifespan of these materials, which is going to reduce plastic waste.” 

The UNSW team uses a powdered additive named a trithiocarbonate – a reversible addition fragmentation chain transfer (RAFT) agent that was originally developed by CSIRO. The RAFT agent enables the nanoscopic network of elements that make up the material to be rearranged and allows the broken pieces to be fused. 

This occurs within around 30 minutes when UV LED lights are shone directly onto the broken plastic, with full healing taking place after roughly one hour. 

Experiments, including on a 3D printed violin, show that the self-repaired plastic’s strength is fully recovered compared to its original unbroken state. 

The team said the process could be commercialised, given the simplification and speed of their system compared to existing methods of repairing broken 3D printed materials. 

“There are other processes that do this, but they rely on thermal chemistry to repair the material and typically it takes around 24 hours and multiple heating cycles to achieve the same type of result,” Corrigan said. 

“Another restriction to that is that you need an oven which is heated to a high temperature, and you obviously cannot repair the plastic material in situ – you would need to disassemble it from the component first, which adds a level of complexity and delay. 

“With our system, you can leave the broken plastic in place and shine the light on the entire component. Only the additives at the surface of the material are affected, so it’s easier and also speeds up the entire process.” 

Boyer says the new technology could potentially be used in a range of applications where advanced 3D printed materials are currently used in high-tech specialised components. These include wearable electronics, sensors and even in shoe manufacturing.