Physicists from the University of Amsterdam have introduced a remarkable piece of Christmas decor: a miniature 3D-printed Christmas tree standing just 8 centimeters tall, crafted entirely from ice. This innovative creation requires no refrigeration or freezing technology, and incurs minimal costs, according to a preprint shared on the physics arXiv.
The process hinges on evaporative cooling, a well-understood phenomenon that helps mammals regulate body temperature. A common daily example is seen with a hot cup of coffee where warmer atoms escape as steam. Evaporative cooling also plays a role in various natural phenomena such as 'wine tears' and is essential for forming Bose-Einstein condensates.
Evaporative cooling is notorious among BBQ enthusiasts for causing the 'stall' during cooking. As meat cooks, it releases moisture that evaporates and cools, counteracting the grill's heat. That's why many competitive pit masters wrap their meat in foil once it reaches an internal temperature of 170° F to overcome this challenge.
Traditional ice-printing techniques often rely on cryogenics or cooled surfaces. However, according to the authors of this study, this is the first instance of employing evaporative cooling in 3D printing. The innovation involved setting up the 3D printing process within a vacuum chamber and using a jet nozzle as the printing head. This approach was discovered accidentally during experiments aimed at eliminating air drag by spraying water in a vacuum environment. 'The printer’s motion control directs the water jet layer-by-layer, constructing the desired shape,' the authors noted in a blog post for Nature.