Rubber bands can become colder than room temperature through sheer mechanical force. Stretching one heats it up (duh) but letting it contract cools it below its starting temperature. Let that weirdness sink in for a moment.
Most people would leave that odd bit of science at “Woah...” and that would be that. But the folks at Applied Science thought, “Hey, someone could scale this up and build a tiny fridge—and that someone is me!”
Of course the thermodynamic gains of such a simple system are minimal. Wood is far from the best insulator, and rubber bands are a less than ideal coolant. What’s neat is that this actually works at all, and we might see a more efficient version of this prototype down the line. Stay weird, science.