From the website:
The body of the tower was made by a new technique called “ferrofluid sculpture” that enables artists to create dynamic sculptures with fluid materials. This technique uses one electromagnet, and its iron core is extended and sculpted. The ferrofluid covers the sculpted surface of a three-dimensional iron shape that was made on an electronic NC lathe. The movement of the spikes in the fluid is controlled dynamically on the surface by adjusting the power of the electromagnet. The shape of the iron body is designed as helical so that the fluid can move to the top of the helical tower when the magnetic field is strong enough.