Levitation has always seemed like an idea from science fiction or sorcery; never something that could be achieved otherwise. Scientists at the University of Tokyo obviously disagreed, since they have created a technology that is able to make small objects float around, using the power of sound waves.
The way they accomplished this feat was by setting up a group of four speakers, which were then set to fire sound, much like a normal speaker. The twist is that the waves were actually ultrasound, those sound frequencies that are above human hearing, and they were standing waves, which bounce back from a surface and return to their source, therefore not transferring energy.
When these waves interfered with each other, two phenomenon’s occur: the waves ‘join together’ to make an extra strong wave, or they cancel each other out. In this last case is where the interesting thing happens.
By cancelling each other, they create a tiny void (known as a node), where there is virtually no wave. So if you insert an object in this air pocket, it can be maintained there by the pressure of the waves outside it pushing it inside. What’s more; if you have 4 speakers, you can change their frequency and this will move the object in three dimensions.
However, this technology won’t be able to levitate a human being anytime soon. At the most, it can sustain an object of 4 centimetres of size. For example, in this experiment, they first used alcohol droplets, feathers and small beads.
This limitation doesn’t mean it’s a useless invention. On the contrary, with further developing, it could be used to manipulate objects in microgravity, or even making purer and more efficient drugs (by mixing them differently).
A video explaining how this works and some examples of its effect on different objects: