An Ice Christmas Tree: Fast Three-Dimensional Printing of Ice Structures via Evaporative Cooling in Vacuum

TL;DR

This work addresses the challenge of 3D printing pure ice without cryogenic infrastructure by using evaporative cooling in vacuum to freeze extruded water on deposition. A commercial 3D printer is modified to eject a 16 µm water jet inside a vacuum chamber (~2–3 mbar) from a microfabricated nozzle, with the freezing driven by latent heat removal governed by the energy balance $m_{\text{evap}} c_p \dfrac{dT}{dt} = - L_v \dfrac{dm_{\text{evap}}}{dt}$, where $L_v = 2.45 \times 10^{6}$ J kg$^{-1}$; only a small fraction of the jet mass needs to evaporate to drive solidification. The setup yields high-fidelity ice geometries (e.g., an ~8 cm tall Christmas tree and cone) with wall thicknesses on the order of ~600 µm and layer height ~200 µm, without supporting materials or external cooling; droplets freeze on the substrate within about 0.5 s, enabling overhangs and tall pillars. The resulting structures are pure ice with notable mechanical stability and optical quality, and the method is scalable and commodity-friendly, offering applications in microfluidics, tissue engineering, and in situ planetary manufacturing, while pointing to future enhancements such as higher resolution, hybrid printing with dissolved additives, and ISRU-inspired adaptations for Martian environments.

Abstract

We demonstrate a novel approach to three-dimensional (3D) printing of freeform 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 demonstrate high-fidelity printing of complex geometries (Christmas trees, cones, vertical pillars, and free-standing zigzag structures) 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.

Figures (6)

• Figure 1: Photograph of a Christmas tree made entirely from 3D-printed ice. The structure is fabricated using a 16 µ m liquid jet mounted on a commercial 3D printer inside a vacuum chamber. The tree has a height of approximately 8 cm and a base diameter of about 6 cm, with branches and fine features faithfully reproduced from the digital model without any supporting material or external cooling. The slight translucency and smooth surfaces demonstrate the optical quality of the ice and the stability of the evaporative-cooling printing process.
• Figure 2: Time-lapse of the 3D-printing process leading up to an ice Christmas, similarly to the tree shown in Figure 1. Total construction time was 26 minutes at 2 mbar.
• Figure 3: Schematic representation of the 3D ice printing setup. A vacuum chamber houses a 3D positioning system where a nozzle, driven by an High-Performance Liquid Chromatography (HPLC) pump, ejects a 16 µm wide water jet. The jet breaks into droplets that freeze onto the substrate via evaporative cooling to form a solid structure.
• Figure 4: Photograph of a conical ice structure printed with the vacuum-based 3D ice printer. The cone (height $\sim 8$ cm, base diameter $\sim 5$ cm) demonstrates that the method can reproducibly generate smooth, axisymmetric geometries without supporting material, with layer lines below the optical resolution of the image and a uniformly translucent ice surface.
• Figure 5: Evaporative cooling of a sessile drop under similar vacuum conditions (2-3 mbar) as used for 3D printing. A macroscopic droplet of 3 mm in diameter was chosen to enable contact thermometry (Pico TC-08), serving as a proxy for the smaller 3D-printing droplets. Recalescence occurs at 110 seconds; the droplet freezes rapidly from an undercooled state, releasing latent heat that drives a sudden temperature rise to $0^{\circ}\text{C}$ (dotted line). The inset shows the experimental schematic.