Ferrofluid is a special kind of liquid full of ferromagnetic particles, so it reacts to magnetic fields. Dakd Jung built a beautiful Bluetooth speaker that features a ferrofluid display driven by an Arduino.

This Bluetooth speaker has a gorgeous minimalistic 3D-printed enclosure that would look great on any bookshelf. But it is the ferrofluid display that makes the speaker special. A glob of ferrofluid floats inside of a glass reservoir mounted front-and-center on the speaker. That ferrofluid moves to the music playing through the speaker, providing a mesmerizing visualization. There is even a dial that lets the user adjust which part of the sound frequency that the ferrofluid responds to.

The ferrofluid is able to react to the tunes thanks to an electromagnet placed behind the glass reservoir. An Arduino Nano board controls the power going to that electromagnet proportionally to the volume in a specific frequency range of the music playing. An MSGEQ7 graphic equalizer module isolates the desired frequency range. The Arduino monitors the voltage output from that module and uses it to control the voltage going to the electromagnet.

The result is that the ferrofluid jiggles and bounces along to the intensity of the music. If the user tunes the dial to low frequences, then the ferrofluid will react to the bass. If set to high frequencies, the ferrofluid will respond to treble. It is entrancing to watch and a very creative use of ferrofluid.