UK Researchers Develop Recyclable Resin for Eco-Friendly 3D Printing

Researchers at the University of Birmingham have created a photopolymer resin from bio-sourced materials that prints at high resolution and can be recycled and reprinted. Their breakthrough, published in the journal Nature, is a step forward in making 3D printing more environmentally friendly.

Chemical composition of the bioresourced resin.

The Need for Change

Traditional photopolymer resins, used widely in 3D printing, come from petrochemicals. Typically made from epoxies or acrylics, these resins harden when exposed to light, forming long-lasting structures. However, their petrochemical origin and poor recyclability are major drawbacks. Once these materials harden, they form irreversible bonds, making them difficult to break down without adding more chemicals. The researchers explain how this process often leads to a “snowballing effect,” where recycling the resin creates even more material, worsening the environmental impact.

To counter this effect, the Birmingham team created a resin that maintains high print quality while being fully recyclable. According to their study, titled “A renewably sourced, circular photopolymer resin for additive manufacturing,” the new resin, derived from lipoic acid—a naturally occurring fatty acid—can be broken down into its original components and reprinted.

During the initial printing process, a small amount of photoinitiator, a compound that helps the resin harden when exposed to light, is used to preserve the resin’s curable properties. This makes the process nearly self-sustainable, as the resin can be repeatedly broken down and reprinted with only a small addition of a photoinitiator, reducing the need for new materials and minimizing waste. Overall, this new material helps create an almost closed-loop system, something the 3D printing industry has been striving for to reduce waste and environmental impact.

Lead researcher and Senior Author of the study, Professor Andrew Dove pointed out, “Our approach is an important step away from relying on 3D printable resins made from petrochemicals, which cannot be efficiently recycled. While we still have improvements to make, this research opens up exciting new avenues for development.”

3D-printed parts of ‘3DBenchy’ for pristine resin compared to recycled resins. Image courtesy of the University of Birmingham.

Practical Applications

The researchers tested the resin using vat photopolymerization to create high-resolution, custom 3D printed parts. They used a commercial digital light processing (DLP) printer, the MiiCraft Ultra 125, made by Taiwanese brand MiiCraft. To assess printing resolution and accuracy, they designed a rectangular base with square arrays and bridges. The smallest feature they could reliably print was a 100 µm wall, showing the impressive x-y resolution of their resin on a regular printer.

They also successfully printed a complex 3D part called “3DBenchy,” a small boat used to benchmark the quality of 3D printers. The model features challenging shapes like overhanging surfaces, bridges, and holes. This high-quality print was achieved at a build rate of 5.1 mm per hour, and the tests showed that the resin could handle precise and detailed printing tasks, making it suitable for several high-resolution applications. Finally, the team used a glass slide and light from the same printer to measure how deep the resin cured. They measured the depth with a micrometer and checked the precision with special imaging tools. As a result, the team said they successfully printed and recycled small objects multiple times without losing quality, proving the potential to reduce waste in the industry.

“3DBenchy,” a 3D printed complex part made entirely from the biosourced feedstock.

This new resin holds promise for various industries. For example, it could be valuable in rapid prototyping, where products are tested before mass production. Although the current material is more flexible than traditional industrial resins, its potential applications are extensive. Future uses could include automotive parts, medical and dental components, and even jewelry design.

“Enabling recycling within the light-mediated 3D printing industry is essential since it is a rapidly expanding method for materials production. We now have the prospect, with our technology, to help ensure that recycling becomes a built-in feature of 3D printing,” said Senior Author and Key Researcher, Assistant Professor Josh Worch.

The Bigger Picture

This development is part of a broader trend towards sustainability in 3D printing. Other companies and research teams are also working on bio-sourced, recyclable resins. For example, companies like Covestro and Arkema have been exploring similar technologies. Covestro has developed a series of resins partially derived from renewable sources, while Arkema’s N3xtDimension line includes some bio-based options. While some progress has been made with renewable biomass, the Birmingham team’s resin successfully addresses the challenge of full recyclability.

A patent application for this resin and its use in 3D printing has been filed by the University of Birmingham Enterprise, the university’s commercialization arm. This step could pave the way for more sustainable 3D printing. The University of Birmingham Enterprise supports research innovations, helping to bring new technologies and products to market based on ongoing university work. As part of this effort, the research team believes that with more study, their resin could meet the rigidity and durability standards of various industries. Although the journey towards completely sustainable 3D printing is ongoing, the University of Birmingham’s new resin is a milestone that could inspire further advancements in the field.

All images courtesy of Machado, T.O., Stubbs, C.J., Chiaradia, V. et al., and the University of Birmingham, from the article “A renewably sourced, circular photopolymer resin for additive manufacturing” published in Nature.