An Ultrasonic Levitator

Abstract

We report the development of an ultrasonic levitation system. Liquid drops or solid samples of diameter less than onehalf wavelength of the excitation frequency are levitated without contact just below the pressure nodes. The piezotransducer is excited by an ultrasonic signal of around 29 kHz through a voltage amplifier. The choice of the numberof half-waves of the acoustic field in the space between the reflector and radiator is made by means of a micrometer.A lamp, an amplifier and a frequency generator are integrated to the levitator. The diameters of the droplets of liquidthat can levitate are of the order of tenths of mm to 3 or 4 mm, depending on the liquid properties (density, surfacetension, etc.). Solid objects can also be levitated. The maximum voltage of the system is 20 Vrms.