Plastic 3D-Printable Elastic Polymer Proves to be Robust

Related Vendors

EPFL Ecole Polytechnique Federale de Lausanne

SIMTOS (Seoul International Machine Tool Show)

Researchers at EPFL have discovered that a soft material originally optimized for 3D printing could solve a long-standing challenge in materials science: creating 3D-printable elastomers that are both tough and durable.

In 2024, researchers from the Soft Materials Laboratory (SMaL) at the School of Engineering at EPFL introduced granular double-network elastomers (DNGEs): rubber-like materials composed of microscopic elastomer particles connected by a softer elastomer network. DNGEs were developed as 3D printing "inks" for structures with precisely tuned mechanical properties.Now, the team has published a follow-up study in Science Advances, showing that the same architecture that gives DNGEs unprecedented mechanical control in 3D printing also offers an unexpected advantage: high resistance to fracture and fatigue. This is a rare combination, as elastomers that are fracture-resistant typically accumulate damage under repeated mechanical stress, limiting their lifespan. On the other hand, fatigue-resistant materials often tend to fracture when subjected to excessive stretching or impacts.

"Originally, our focus was on improving processability, but once we had the granular structure, we discovered that these materials are also very tough," says Esther Amstad, head of the Soft Materials Lab. "Then we realized that much of this toughness is based on repetitive energy dissipation mechanisms – the material can absorb energy repeatedly without breaking irreversibly."Amstad explains that the DNGEs overcome the typical trade-off between toughness and fatigue resistance thanks to their unique, diverse internal structure. "Essentially, the two different networks—one made of granular elastomer particles and one made of soft elastomer—share the mechanical strain between them, making the material overall stronger."

By expanding the range of usable materials, we can not only reduce the ecological footprint of the DNGEs but also make them more accessible to any laboratory with a commercially available 3D printer.

Esther Amstad

More Durable High-Performance Materials

In experiments, optimized DNGEs demonstrated fracture toughness values up to 15 times higher than comparable elastomers, as well as up to three times greater fatigue resistance.When stretched, the materials redistribute mechanical stress from the stiff microparticles to the softer regions in between. In these softer areas, strain energy can be repeatedly dissipated through the sliding and reorganization of polymer chains, rather than through the irreversible breaking of polymer bonds, which limits permanent damage. The granular structure of the DNGEs also alters the way cracks propagate through the material. Instead of following a straight path, cracks preferentially travel through the softer areas between the elastomer microparticles. This creates a winding path that slows their progression and delays failure.
The findings suggest that the material architecture developed at SMaL, originally designed for advanced 3D printing, could also provide a new strategy for designing more durable soft materials. Such materials could extend the lifespan of soft robots, electronics, and biomedical devices, whose components are subjected to repeated stresses and deformations over long periods.The team is already working on further optimizations with a focus on sustainability, such as using biodegradable elastomers or those made from recycled materials."Our goal is to use more sustainable materials without compromising mechanics," says Amstad. "By expanding the range of usable materials, we can not only reduce the environmental footprint of DNGEs but also make them more accessible for any lab equipped with a standard 3D printer."

Additive manufacturing

Basic knowledge 3D printing