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UK researchers develop bio-sourced and recyclable resin for 3D printing

It is based on lipoic acid, a fatty acid molecule that is commonly sold as a dietary supplement

Davide SherNovember 12, 2024

1 minute read

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Researchers from the University of Birmingham, UK, have designed a new type of photocurable recyclable resin that offers two key benefits over existing 3D printing resins: It is made entirely from bio-sourced materials and can be 3D printed, recycled, and then printed again. Their study was published in Nature.

a, Conventional resins for 3D printing: irreversible photoinduced crosslinking of typical photoresins for additive manufacturing by stereolithography (SLA) or Digital Light Processing (DLP) using acrylate or epoxy-functional (macro)monomers. b, Open-loop recycling in 3D printing uses preformed dynamic bonds in photoset materials to enable resin recycling after depolymerization and the addition of reactive diluents to create new photocurable material. c, Closed-loop recycling in 3D printing (this work) presents a method to achieve polymerization–depolymerization cycles of dynamic disulfide bonds that enable the creation of renewably sourced resins suitable for closed-loop chemical recycling.

While current 3D printing usually relies on epoxies or acrylics, which come mostly from petrochemical feedstock, the new resin is made from lipoic acid, a naturally occurring fatty acid molecule that is 100% bio-sourced, and commonly sold as a dietary supplement.

Additionally, the recyclability of conventional resins is still limited, because they rely on irreversible bonds created when the resin cures (hardens), and this poses challenges when the material needs to be recycled.

In contrast, the resin designed by the Birmingham team can be printed, then broken back down to its constituent parts, recycled and reprinted, with the addition of just a small amount of photoinitiator to maintain the material’s curable properties, meaning 3D printed products can be recycled in an almost fully closed-loop system.

The new resin is compatible with light-initiated printing techniques such as DLP, SLA or by direct ink write, or InkJet printing, and provides high fidelity, with resolution down to 0.05mm.

The researchers who invented the resin were led by Professor Andrew Dove from Birmingham’s School of Chemistry.

Discover the breakthrough in 3D printing with recyclable resin made from bio-sourced materials, by Researchers from the University of Birmingham — a, 1H NMR spectroscopic analysis of pristine resin (300 MHz, 300 K, CDCl3) compared to recycled resins (400 MHz, 298 K, CDCl3). b, SEC images of pristine resin compared to recycled resins (CHCl3 + 0.5% v/v NEt3, against polystyrene standards). c, Photorheology at an ambient temperature of pristine resin compared to recycled resins under oscillatory shear (0.2 Hz with an amplitude of 25% for 50 s) without irradiation, then the sample was irradiated after 50 s. d, Z depth cure screening of pristine compared to recycled resins by irradiating a 2D-square and measuring sample thickness (z axis depth) versus irradiation time (5–60 s). e, x–y printing accuracy for pristine resins compared to recycled resins determined by comparing the surface area of squares to theoretical square size (pixel size 30 µm). The theoretical surface area of each square and number of squares (sample size): 4 mm2 (n = 3); 1 mm2 (n = 4); 0.25 mm2 (n = 5); 0.0625 mm2 (n = 6). The average surface area’s center value and error bars indicate 1 standard deviation. f, 3D-printed parts of ‘3DBenchy’ for pristine resin compared to recycled resins. A photoinitiator was added to recycled resins (1.5 wt% for the first recycle; 2.5 wt% for the second recycle) for photorheology and printing.

They have shown that the recyclable resin can complete two ‘recycles’ and anticipate further recycling is possible. This means the material could be used in sustainable packaging, rapid prototyping industries, optical and electronic devices, construction and architecture, or fashion and jewellery.

University of Birmingham Enterprise has filed a patent application covering the composition of the recyclable resin, and its use in 3D printing, and is now seeking to license or co-development partners. For commercial or licensing enquiries contact Jon Roberts.