Recyclable ink made from lignin: Sustainable 3D printing without fossil polymers

Researchers at the Helmholtz Centre Hereon have developed a recyclable ink for 3D printing. The material is based on the industrial by-product lignin and can be reused multiple times. The results show potential for sustainable additive manufacturing and have been published in ACS Sustainable Chemistry & Engineering.

Additive manufacturing processes such as 3D printing are becoming increasingly important in many industries, including medical technology, vehicle construction, and consumer goods. Material development plays a central role in this. Researchers at the Helmholtz Centre Hereon have now developed a recyclable 3D printing ink that consists mainly of lignin, a by-product of paper production or biomass processing.

The researchers' goal was to develop a sustainable alternative to conventional printing materials, which are often based on fossil polymers and are usually neither recyclable nor biodegradable.

Around 70 percent of the new ink consists of lignin. During the printing process, the material exhibits high fluidity, allowing it to be easily extruded through the nozzles of a 3D printer. After printing, the ink quickly regains its solid structure. Printed objects also remain dimensionally stable at temperatures of up to around 200 °C.

The ink developed is specially designed for direct ink writing (DIW). This process is one of the additive manufacturing techniques in which objects are printed at room temperature using paste-like materials.

Unlike many other lignin-based materials, the new ink does not require chemical or thermal post-treatment to cure. This means that the material remains completely recyclable.

Dr. Maria Balk from the Hereon Institute for Functional Materials for Sustainability explains: "We wanted to demonstrate that waste-derived materials like lignin can meet the technical demands of modern 3D printing while improving sustainability."

She adds: "To do this, we transformed an industrial waste product into a water-based 3D printing ink that can be fully recycled simply by adding water."

A key feature of the new ink is that it is fully recyclable. Printed components can be reused multiple times by dissolving them in water and reprocessing them.

"One of the most exciting findings is that the printed objects can be recycled multiple times through rehydration without losing performance," explains Balk.

This property is rare in additive manufacturing and could open up new approaches for circular production. According to the researchers, this could also reduce CO₂ emissions.

According to the Helmholtz Centre Hereon, this development opens up new perspectives for the sustainable 3D printing of components, for example for:

• Product prototypes
• Technical components
• Applications in various industrial sectors
• Potentially also medical technology applications

Prof. Francesca Toma, head of the Hereon Institute for Functional Materials for Sustainability, emphasizes the overarching approach: "Industrial waste streams are an untapped opportunity. Lignin is one of the most abundant components of wood, yet largely underused. Turning it into a fully recyclable material shows how waste can drive innovation in an industry that urgently needs sustainable solutions."

The researchers are now planning further tests and optimizations. The aim is to scale up the manufacturing process and investigate possible areas of application.

COMPAMED-tradefair.com; Source: Helmholtz-Zentrum Hereon