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Concept
Acoustic levitation
Summary
Acoustic levitation is a method for suspending matter in air against gravity using acoustic radiation pressure from high intensity sound waves.
It works on the same principles as acoustic tweezers by harnessing acoustic radiation forces. However acoustic tweezers are generally small scale devices which operate in a fluid medium and are less affected by gravity, whereas acoustic levitation is primarily concerned with overcoming gravity. Technically dynamic acoustic levitation is a form of acoustophoresis, though this term is more commonly associated with small scale acoustic tweezers.
Typically sound waves at ultrasonic frequencies are used thus creating no sound audible to humans. This is primarily due to the high intensity of sound required to counteract gravity. However, there have been cases of audible frequencies being used. There are various techniques for generating the sound, but the most common is the use of piezoelectric transducers which can efficiently generate high amplitude outputs at the desired frequencies.
Levitation is a promising method for containerless processing of microchips and other small, delicate objects in industry. Containerless processing may also be used for applications requiring very-high-purity materials or chemical reactions too rigorous to happen in a container. This method is harder to control than others such as electromagnetic levitation but has the advantage of being able to levitate nonconducting materials.
Although originally static, acoustic levitation has progressed from motionless levitation to dynamic control of hovering objects, an ability useful in the pharmaceutical and electronics industries. This dynamic control was first realised with a prototype with a chessboard-like array of square acoustic emitters that move an object from one square to another by slowly lowering the sound intensity emitted from one square while increasing the sound intensity from the other, allowing the object to travel virtually "downhill".
Official source
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Explores acoustic holograms, ultrasound applications, Airy beams, lenses, mask design, and results with acknowledgements.
Acoustic Tweezers: Manipulating Micro-Objects
Explores acoustic tweezers for manipulating micro- and nano-objects using standing waves, traveling waves, and multiple transducers.
Related publications (8)
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Related concepts (1)
Ultrasound
Ultrasound is sound with frequencies greater than 20 kilohertz. This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is often used in medicine.