Sound waves can be used to levitate and move small objects, scientists have shown.
Acoustic levitation has numerous potential applications ranging from materials processing to biochemistry, according to the Swiss team.
The technique uses pressure waves between an emitting surface and reflector to cancel out gravity.
Objects trapped in stable regions of the energy field called nodes can be lifted and moved around with precision.
In tests the scientists levitated liquid droplets, and also a toothpick.
Professor Dimos Poulikakos, from the Laboratory of Thermodynamics in Emerging Technologies in Zurich, led the research reported in the journal Proceedings of the National Academy of Sciences.
The scientists wrote: “Contactless transport and handling of matter are of fundamental importance to the study of many physical phenomena and biochemical processes.
“Typical state-of-the-art methods of contactless handling of matter are based on electromagnetic principles and have interesting capabilities but also clear limitations in terms of particle size and/or inherent requirements of special material properties.
“Acoustic levitation is both contact-free and material independent, also without requiring laborious sample preparation.”