Scientists have known for years how to use sound waves to hoist particles in the air, a process known as acoustic levitation. But moving the lifted bits around was more challenging. The sound waves tend to trap a levitated object in a fixed pocket of space.
The new technique moves the pockets around by deforming a field of sound waves, letting researchers transport trapped objects several centimeters
There’s a cool slow-motion video of a small blob of sodium and a drop of water being moved together and reacting when they touch. Presumably much easier to film when you know where the low-speed collision is going to take place.