Optical trapping is a technology which has allowed scientists to move tiny objects around for many years, enabling manipulation with no contact. In fact, one of the recipients of the 2018 Nobel Prize for Physics, Arthur Ashkin, was recognised for his work on optical trapping. Despite the many possibilities opened up by this technology, it has some limitations. Chiefly, it places limits on the properties of objects which can be manipulated.
Acoustic trapping is an alternative technology which uses sound waves instead of light waves; the technology is sometimes referred to as 'acoustic tweezers'. Scientists hope that they may be able to manipulate individual cells and other tiny objects using the technology. Sound waves, unlike light waves, can be applied to a wider range of object sizes and materials, even for particles of millimetre size.
Ultrasound frequencies tend to be used for manipulating particles, as the very high amplitude of sound required...