Could 3D printing plastic enter a “zero-waste” era? ZJU’s recyclable resin published in

From custom medical devices to aerospace components, 3D printing has revolutionized manufacturing with its ability to produce intricate, tailored designs rapidly. Yet as the technology becomes increasingly mainstream, a major challenge looms: waste. Like conventional plastics, discarded 3D-printed materials are piling up, with limited options for recycling.

Now, a team from Zhejiang University has worked out a solution. Led by Professor XIE Tao and Professor ZHENG Ning from the College of Chemical and Biological Engineering, the team has developed a novel thermally reversible photo-click reaction that enables infinitely recyclable 3D printing resin without sacrificing performance. Their findings, published in Science on April 11, could mark a major step toward a truly circular economy in additive manufacturing. The study’s first author is PhD student YANG Bo, with XIE Tao and ZHENG Ning as corresponding co-authors.  

Unlike traditional subtractive manufacturing, which cuts away excess material, photocurable 3D printing builds objects layer by layer using liquid resin and light, akin to assembling Lego bricks. However, despite decades of progress, the field still faces limitations such as slow production speeds, limited material strength, and high resin costs, which hinder broader industrial applications.

XIE Tao’s team has long been tackling these challenges. Last year, they unveiled a super-stretchable 3D printing material in Nature, capable of elongating over nine times its original length. Now, they’re taking sustainability a step further.

“If we could infinitely recycle 3D printing materials,” XIE Tao explains, “we’d cut down on both costs and waste—a win-win for both industry and the environment.”

The dissociative thiol-aldehyde photochemistry

The team’s breakthrough came unexpectedly. During an experiment, YANG Bo added a thiol reagent and the results defied expectations. “The reaction behaved the opposite of what we predicted,” YANG Bo recalls. Upon deeper investigation, the team realized they’d stumbled upon a light-triggered click reaction between thiols and aldehydes, a typical chemical reaction that generally required heating.

“This was the first time anyone showed that this reaction could occur rapidly under light,” says ZHENG Ning. That serendipitous finding opened the door to a new class of recyclable, high-performance 3D printing resins.

Typical 3D photoprinting relies on photopolymerization of (meth-)acrylate monomers and cross-linkers, which produce carbon-carbon bonds that are practically impossible to break down for recycling. XIE Tao’s team took a different approach. Their system forms dithioacetal bonds — molecular “clips” that link polymer building blocks under light but unclip with gentle heating, reverting the material back to its original components.

“It’s like disassembling Legos,” XIE Tao says. “The printed object can be recovered at the molecular level and reprinted again and again.”

Modular polymer network design

Crucially, this modular design allows tuning the polymer backbone without compromising recyclability. By fine-tuning molecular structures, they created elastomers, crystalline polymers, and rigid plastics, all from the same base chemistry. Potential applications range from lost foam casting (e.g., for metal engine parts) to orthodontic aligners.

Professor XIE Tao (middle) and his team

“Our research has successfully overcome the longstanding trade-off between mechanical performance and closed-loop recyclability in photocurable 3D printing materials at the molecular level,” said XIE Tao. “By establishing a light-responsive dynamic dithioacetal chemistry system, we offer a novel molecular design strategy, providing meaningful insights for advancing sustainable manufacturing technologies.”