A University of Amsterdam team used evaporative cooling in a vacuum to 3D‑print a 3.14‑inch ice Christmas tree by replacing a printer nozzle with a 16‑µm water jet. The jet cools by tens of °F in under a second and deposited water remains liquid for about 0.5 seconds, allowing droplets to merge before rapid crystallization. The additive‑free ice prints can serve as sacrificial templates for hollow channels, may aid tissue scaffolds, and could enable in‑situ printing on Mars.
Physicists 3D‑Print a Tiny Ice Christmas Tree Using Evaporative Cooling — No Additives Needed
The process harnesses an everyday physics concept known as evaporative cooling.
A team of physicists in the Netherlands has demonstrated a striking new manufacturing trick: 3D‑printing a diminutive Christmas tree made entirely of ice particles. Published in Nature, the proof‑of‑concept shows how evaporative cooling inside a vacuum can freeze a fine water jet quickly enough to build stable ice structures without cryogenics or chemical additives.
How It Works
The researchers at the University of Amsterdam exploited evaporative cooling — the familiar physical effect in which molecules leaving a liquid as vapor remove heat from the remaining liquid. Examples range from steam above a hot cup of coffee to the cooling of skin by sweat, and even to laser cooling of atoms in advanced physics experiments.
While studying water spraying in a vacuum to reduce aerodynamic drag, the team noticed that a very thin water jet (about 16 micrometers across) cooled extremely fast. Because of its high surface‑to‑volume ratio, the jet can lose tens of degrees Fahrenheit (tens of °F) in under a second. The stream freezes almost immediately after striking a surface.
From Jet To 3D‑Printed Ice
Seeing this rapid freezing, the researchers substituted a conventional 3D‑printer nozzle with the thin water jet and enclosed the printer in a transparent vacuum chamber. With a design loaded, the printer’s motion control guides the jet just as it would guide a resin extruder.
“Previous ice‑printing methods relied on cooled substrates or cryogenic infrastructure (liquid nitrogen, helium),” the team writes. “Our approach integrates the jet into a commercial 3D printer housed inside a transparent vacuum chamber.”
Crucially, deposited water remains liquid for roughly 0.5 seconds before solidifying. During that brief window, droplets created by the jet coalesce into a continuous filament by surface tension; crystallization then initiates and propagates rapidly through the new layer, building up the object.
Results And Applications
Their demonstration model is a roughly 3.14‑inch (about 8 cm) tall ice Christmas tree. Beyond the novelty, the technique has practical potential: printed ice can serve as a sacrificial template inside resin or polymer builds, then be melted away to leave clean, hollow channels without residue or post‑processing. The same approach could inform tissue‑engineering scaffolds or fluidic channels for microfabrication. No additives are required, and when the vacuum is released the ice melts to pure water.
Remarkably, the team also notes extraterrestrial potential: Mars’s surface pressure lies within the printer’s operating range, suggesting astronauts could use local ice deposits to print structures in situ instead of transporting heavy cryogenic equipment from Earth.
Why It Matters
This method removes the need for cooled build plates or bulky cryogenics and eliminates additive residues. By combining a simple physical principle with off‑the‑shelf 3D‑printer motion control, the researchers opened a low‑waste route to temporary templates, delicate channels, and possibly even off‑world fabrication.
