EPFL's 3D Printed Elastomer Combines Toughness and Fatigue Resistance

A novel rubbery material engineered for 3D printing by researchers at EPFL's Soft Materials Laboratory (SMaL) demonstrates a rare combination of toughness and durability. This development addresses a long-standing challenge in materials science, where printable elastomers often sacrifice one property for the other.

The material, known as double network granular elastomers (DNGEs), features microscopic elastomer particles embedded within a softer elastomer network. This architecture, initially designed for enhanced printability, unexpectedly confers significant resistance to both fracture and fatigue. Typically, elastomers designed to resist fracture tend to degrade under repeated stress, while fatigue-resistant materials can be prone to snapping under sudden strain.

According to SMaL head Esther Amstad, the material's dual-network structure allows it to share mechanical strain between the rigid microparticles and the surrounding soft zones. This distribution enables the material to dissipate energy repeatedly without irreversible damage. When subjected to stress, cracks are rerouted through the softer regions, slowing their propagation and delaying failure.

Testing revealed that optimized DNGEs exhibit fracture toughness up to 15 times higher and fatigue resistance up to three times greater than comparable elastomers. While the material is slightly softer than bulk double-network elastomers, researchers are exploring multi-material printing to regain some rigidity. Current limitations include a maximum part thickness of approximately 5 millimeters due to UV curing depth, and performance degradation at very high strains where covalent bonds within the particles begin to break.