Producing Acoustic 'Frozen Waves': Simulated experiments

TL;DR

This paper demonstrates how superpositions of Bessel beams can generate customizable, static ultrasonic pressure fields called 'Frozen Waves' with high transverse localization, useful for medical and technological applications.

Contribution

It introduces a method for creating arbitrary longitudinal ultrasonic patterns using Bessel beam superpositions, including detailed analysis of transducer design and potential applications.

Findings

Successfully simulated generation of Frozen Waves in water-like media.

Identified optimal transducer aperture sizes and ring dimensions.

Showed potential for medical and technological applications like ultrasound therapy.

Abstract

In this paper we show how appropriate superpositions of Bessel beams can be successfully used to obtain arbitrary longitudinal intensity patterns of nondiffracting ultrasonic wavefields with very high transverse localization. More precisely, the method here described allows generating longitudinal acoustic pressure fields, whose longitudinal intensity patterns can assume, in principle, any desired shape within a freely chosen interval 0 < z < L of the propagation axis, and that can be endowed in particular with a s t a t i c envelope (within which only the carrier wave propagates). Indeed, it is here demonstrated by computer evaluations that these very special beams of non-attenuated ultrasonic field can be generated in water-like media by means of annular transducers. Such fields "at rest" have been called by us << Acoustic Frozen Waves >> (FW). The paper presents various cases of FWs in water, and investigates their aperture characteristics, such as minimum required size and ring dimensioning, as well as the influence they have on the proper generation of the desired FW patterns. The FWs are particular Localized Solutions to the wave equation that can be used in many applications, like new kinds of devices, such as, e.g., acoustic tweezers or scalpels, and especially various ultrasound medical apparatus; e.g. for attempting the destruction of tumor cells without affecting the preceding and subsequent (and surrounding) tissues. Keywords: Ultrasound; Frozen Waves; Bessel beam superpositions; Non-diffractive waves; Localized Waves; Annular transducers.