Non-diffractive acoustic beams produce negative radiation force in certain regions

A method of particle manipulation, one based on the force of acoustic radiation, has drawn wide attention. However, the real concept behind “acoustic tweezers”—negative acoustic radiation force (ARF)—has not been realized in experiments. In this paper, a prediction of a negative ARF generated by the non-diffractive acoustic beam is proposed. Its underlying physical mechanism is also analyzed in detail. On the basis of an analysis of energy flux density, the analytical region of negative radiation produced by the non-diffractive beam is solved completely. Forecast methods based on this solution are proposed that lay the foundation for realizing acoustic tweezers and offer the possibility of designing devices that produce negative ARFs. In addition, the negative propagation of acoustic beams in normal materials is realized, raising a possible alternative means to accomplish acoustic beam control.