3D printing with ice: Amsterdam physicists use vacuum instead of cooling

Researchers at the Institute of Physics of the University of Amsterdam have demonstrated an unusual example of additive manufacturing: a Christmas tree printed entirely from ice, produced without conventional cooling technology. Instead of refrigeration units, the team led by Menno Demmenie, Stefan Kooij, and Daniel Bonn used only water and a vacuum pump. The experiment is meant as more than a gimmick—it serves as a vivid demonstration that makes fundamental physical processes visible.

Technically, the method is based on evaporative cooling. In a vacuum chamber at strongly reduced pressure, water evaporates very rapidly even at room temperature. Each evaporating molecule removes heat from the remaining water, causing it to cool progressively. Eventually, the temperature drops below the freezing point even though the water initially remains liquid. The researchers refer to this as supercooled water. When the extremely thin water jet—about 16 micrometers, comparable to a human hair—hits an already frozen surface, it solidifies immediately.

In this way, a three-dimensional ice structure is created layer by layer. The printed tree is about eight centimeters tall and was built in roughly 26 minutes. No support material is needed because each new layer freezes instantly and remains stable. When the vacuum pump is switched off and the pressure is returned to normal, the object melts back in a controlled manner into clean water. Time-lapse recordings show both the printing process and the subsequent melting.

Daniel Bonn emphasizes the experiment’s educational value: phase transitions, heat transfer, and the influence of ambient pressure can be observed directly in the transparent chamber. Beyond that, the researchers also see practical prospects. Pure ice structures could serve, for example, as temporary scaffolds in biology or be used in microfluidics by selectively melting out channels after fabrication. The physicists even point to possible applications for extraterrestrial scenarios, since low pressure and cold—such as on Mars—provide natural conditions for similar processes.