3D-printed NiTi alloys for elastocaloric cooling

NiTi-based elastocaloric cooling presents an environmentally friendly solid-state alternative to vapor-compression refrigeration. However, conventional NiTi refrigerant fabrication relies on thermomechanically intensive processes that limit geometric versatility while increasing production time, costs, and material waste. Although 3D printing offers a potential solution, existing 3D-printed NiTi alloys face a critical trade-off between cyclic durability and specific temperature change (the adiabatic temperature change per unit driving stress). Here, we address these challenges by developing a high-performance 3D-printed NiTi alloy with defect-minimized, bimodal microstructures. This design facilitates stress-induced martensitic phase transformation while suppressing dislocation slip and crack propagation. Consequently, the alloys can withstand a record-high 3 million cycles without failure, while simultaneously achieving an 11-fold enhancement in specific temperature change over state-of-the-art 3D-printed counterparts (increasing from 2.97 to 33.6 °C·GPa−1). Furthermore, we realize direct 3D printing and integration of NiTi refrigerants into a macroscale cooling prototype, which achieves a temperature span of 20 °C. Our work establishes 3D-printed NiTi alloys as viable elastocaloric refrigerants, unlocking a 3D-printing-enabled pathway toward sustainable cooling systems. Materials with high cycling durability and large specific temperature change are critical for advancing solid-state cooling. The authors achieve such properties in 3D-printed NiTi alloys through microstructural engineering and demonstrate a functional prototype based on the alloys.