Physicists from the University of Amsterdam have come up with a very cool Christmas decor: a miniature 3D-printed Christmas tree of only 8 centimeters high, made of ice, without any cooling equipment or other freezing technology, and at minimal costs. The secret is evaporative cooling, according to a preprint posted on physics arXiv.
Evaporative cooling is a well-known phenomenon; mammals use it to regulate body temperature. You can see it in your cup of hot coffee in the morning: the hotter atoms rise to the top of the magnetic trap and “pop out” as steam. It also plays a role (along with shock wave dynamics and several other factors) in the formation of 'wine tears'. It is an important step in creating Bose-Einstein condensates.
And evaporative cooling is also the main culprit behind the infamous “stall” that so often plagues aspiring BBQ pitmasters eager to make a successful pork butt. The meat sweats as it cooks, releasing the moisture inside, and that moisture evaporates and cools the meat, effectively neutralizing the heat of the barbecue. That's why a growing number of competitive pitmasters are wrapping their meat in aluminum foil after the first few hours (usually when the internal temperature reaches 170 degrees Celsius).° F).
Ice printing methods usually rely on cryogenic techniques or cooled substrates. According to the authors, this is the first time that evaporative cooling principles have been applied to 3D printing. The trick was to house the 3D printing in a vacuum chamber using a jet nozzle as a print head – something they discovered by chance when they tried to reduce air resistance by spraying water into a vacuum chamber. “The printer's motion control guides the water jet layer by layer, building geometry on demand,” the authors wrote in a blog post for Nature, adding:
