This is the build that took acoustic levitation out of the specialist lab. Two opposed arrays of ultrasonic transducers driven in phase produce a standing wave with pressure nodes spaced half a wavelength apart, and small light objects sit in those nodes. The write-up runs to 27 steps with photographs, and the promised payload list is water, ants and tiny electronic components.
As a physical demonstration it is closely related to everything else in this feed: a standing wave, nodes and antinodes, and matter sorting itself into the quiet places. The difference is that the pattern is in air and three-dimensional rather than on a plate.
One caution. This runs at ultrasonic frequencies at real power, and you will not hear when it is loud. Treat exposure seriously, keep the arrays enclosed during long runs, and do not assume that silence means safety. Published 2017, updated since.