Physicists 3D-printed a Christmas tree of ice

Physicists from the University of Amsterdam have come up with a really cool Christmas decoration: a miniature 3D-printed Christmas tree, just 8 centimeters high, made of ice, without any refrigeration equipment or other freezing technology, and at minimal cost. The secret is evaporative cooling, according to a preprint published on the physics site arXiv.

Evaporative cooling is a well-known phenomenon; mammals use it to regulate body temperature. You can see it in your morning cup of hot coffee: the hottest atoms rise to the top of the magnetic trap and “jump” as vapor. It also plays a role (along with shock wave dynamics and various other factors) in the formation of “wine tears”. This is a key step in the creation of Bose-Einstein condensates.

And evaporative cooling is also the main culprit for the infamous “stall” that so often afflicts aspiring barbecue masters eager to get their pork butt right. The meat sweats while cooking, releasing the moisture it contains, and this moisture evaporates and cools the meat, negating the heat of the barbecue. This is why a growing number of competitive pit chefs wrap their meat in foil after the first few hours (usually when the internal temperature reaches 170°C).° F).

Ice printing methods typically rely on cryogenics or cooled substrates. According to the authors, this is the first time that the principles of evaporative cooling have been applied to 3D printing. The trick was to house the 3D print in a vacuum chamber using a jet nozzle as a print head – something they discovered by chance while trying to get rid of air drag by spraying water into a vacuum chamber. “Controlling the printer’s movement guides the water jet layer by layer, creating geometry on demand,” the authors wrote in a blog post for Nature, adding: