An ultrasonic transducer and a reflector set up a standing wave; drop a bead of liquid into a pressure node and it stays there. That much is a familiar party trick. What Sandlin adds is the high-speed footage — the Phantom V2511 running at 20,000 frames per second, which he says he deliberately throttled — showing the droplet oscillating, flattening and wobbling in ways invisible at normal speed.
This is a cousin of cymatics rather than the thing itself: no medium is being patterned, a single object is being trapped. But it is the same underlying physics of nodes and antinodes in a standing wave field, applied in three dimensions and at ultrasonic frequencies, and it is the clearest footage available of what a pressure node does to matter sitting in it.
Sandlin also credits the device to a Patreon supporter, Anthony, which is a small reminder of how much of this field runs on amateur builders with a lathe.