Additive manufacturing of ultralong and architected single crystals

Single-crystal materials are indispensable for high-performance applications, yet their deployment remains constrained by conventional manufacturing techniques that depend on strict quasi-steady thermal conditions¹. This requirement fundamentally conflicts with the intense cyclic thermal fluctuations inherent to additive manufacturing², historically preventing the 3D printing of large or architected single crystals. Here we present a free-form additive manufacturing approach that resolves this contradiction by using delicately controlled alternating and pulsed heat inputs to govern and direct single-crystal growth. Using this method, we demonstrate the fabrication of metre-tall, centimetre-diameter single-crystal Ti-6Al-4V alongside, to our knowledge, the first single-crystal lattice structures containing complex zigzag ligaments, effectively eliminating theoretical size constraints for single-crystal components. The resulting bulk single-crystal Ti-6Al-4V exhibits an order-of-magnitude increase in creep resistance over standard grain-size scaling predictions, driven by the synergistic elimination of grain boundaries and an additive manufacturing-induced hierarchical α/β-architecture that regulates dislocation density, mobility and void evolution. Furthermore, we demonstrate the broad applicability of this technique by printing single crystals of hard-to-process refractory metals, including W, Mo, Nb and MoNb alloys. Our work introduces a large-scale method for single-crystal additive manufacturing, expanding the accessible materials library and enabling high-performance, complex geometries previously unattainable by classical methods.