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Physics

Solid sphere floats on sound

25-kHz sound wave floats 5-cm-diameter ball

Applied Physics Letters 25-kHz sound wave floats 5-cm-diameter ballApplied Physics Letters

Acoustic levitation, which is produced by sound waves, has grown more sophisticated. Three ultrasonic transducers arranged in a tripod formation and set to emit at a frequency of 25 kilohertz (kHz) suspended a polystyrene sphere five centimeters in diameter (Applied Physics Letters, July 2016). “We’ve shown that it is possible to use sound waves to levitate much larger objects than thought previously,” says physicist Marco Aurélio Brizzotti Andrade, of the University of São Paulo (USP), first author of the study (see PESQUISA FAPESP nº 228). According to Andrade, acoustic levitation using ultrasonic waves had so far managed to float bodies with a diameter of four millimeters at most. Professor Anne Bernassau, of Heriot-Watt University in Scotland, also took part in the study. Among possible applications of this new approach to the technique, the authors mentioned contactless chemical reactions, transportation and handling of corrosive substances, contactless handling of liquid substances, and the production of new kinds of drugs.

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