UvA physicists 3D-printed an 8 cm Christmas tree from pure ice, using evaporative cooling instead of refrigeration.
A team of physicists at the University of Amsterdam (UvA) have created what could very well be this year’s coolest—certainly its coldest—Christmas decoration: an eight-centimeter-tall 3D printed tree made purely of ice. The method for creating the delicate ice tree did not use any refrigeration or freezing technology, instead relying on the natural process of evaporative cooling.
This is not the first time that we’ve seen 3D printed ice. Back in 2022, a team of researchers from Carnegie Mellon developed a process for 3D printing tiny ice structures that could be used as sacrificial templates within fabricated parts, a kind of reverse molding. This printing technique relies on a custom build platform with a temperature of -35°C, which instantly freezes tiny water droplets as they are deposited.
In the ice printing method developed by the UvA scientists, they have chosen to forego cooled substrates and cryogenics, instead opting to print inside a vacuum chamber to leverage evaporative cooling principles. Evaporative cooling is a common phenomenon that we encounter practically every day, for instance, when we sweat or when steam rises from a hot cup of coffee. Evaporative cooling was also behind a number of proto-air conditioners used thousands of years ago. Now, UvA researchers Menno Demmenie, Stefan Kooij, and Daniel Bonn have applied this principle to create 3D structures made from ice.
In their work, the research team used a low-pressure vacuum chamber to create an environment in which water evaporates very quickly at room temperature. Within this vacuum chamber, they used a micrometer-sized water jet to deposit water molecules, which would evaporate and in doing so take a small amount of heat with them. Any remaining water molecules would cool rapidly, eventually to below freezing point. “At that point the water is still liquid, but supercooled,” UvA writes. “As soon as the ultra-thin stream (about as thin as a human hair: 16 micrometers) hits the already formed layer of ice, it freezes instantly.”
This process was repeated layer by layer until a complex ice tree was created. If that wasn’t impressive enough, it was made in just 26 minutes and without supports or waste. Like most things made of ice and snow, the 3D printed tree was not designed for durability: as soon as you turn the vacuum pump off, the structure simply melts back into water.
While the 3D printed Christmas tree is a novel example of this evaporative cooling 3D printing technology, there are more practical applications for this process. As the researchers explain, their printing method offers a high level of visibility, which allows you to visualize phase transitions, heat transfer and the influence of pressure. The process therefore could have important applications in biology, where pure ice structures could be used as scaffolding for bioprinted tissues, as well as microfluidics, where intricate channels could be printed from ice and then melted. The researchers also cite building structures on Mars using their evaporative cooling technique. The Christmas tree use case was documented in a recent study.
