Three-dimensional printing of ice structures via evaporative cooling in vacuum.

We demonstrate an approach to three-dimensional (3D) printing of ice structures by exploiting evaporative cooling. A micrometer-sized water jet is used to 3D print inside a vacuum chamber. The reduced ambient pressure leads to rapid evaporation of the extruded water, extracting latent heat, and quickly cooling the water well below 0 °C. Once deposited, the water freezes almost instantaneously into stable ice structures. We achieved high-fidelity printing via two distinct deposition techniques: layer-by-layer deposition for intricate 3D structures (e.g., a Christmas tree), and support-free mid-air printing for upright profiles (e.g., an in profile face), all achieved without cryogenic infrastructure, supporting materials, or external refrigeration. This approach directly visualizes fundamental thermodynamic principles-latent heat, evaporative cooling, and pressure-dependent phase transitions-while offering a relatively simple and scalable platform for ice-templated microfluidics and tissue engineering, or even extraterrestrial 3D printing.