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Ultrasonic Levitator

The ultrasonic levitator is a powerful tool that facilitates investigations on single particles or droplets, e.g. crystallisation experiments. Since it suspends an object in a fixed position, the process under investigation is not disturbed by the influence of surface contact. The ultrasonic levitator with its various optional features is designed to be applicable to several scientific disciplines.

General Working Principle

The principle of acoustic levitation is based on forces that affect the sample in a standing ultrasonic wave. As a result of multiple reflections between an ultrasonic radiator and a solid, flat or concave reflector - which is adjusted concentrically at a distance of some multiple half wavelengths - a standing wave with equally spaced nodes and antinodes of the sound pressure and velocity amplitude is generated. Solid or liquid samples with effective diameters of less than half a wavelength will be levitated between the pressure nodes without contact as a result of axial radiation pressure and radial Bernoulli stress.  Minimal acoustic power is required for levitation with the sound wavelength at about three times the sample diameter.
Schematic setup and pressure distribution in the resonator
Schematic setup and pressure distribution in the resonator