Numerical investigation of the inertial cavitation threshold under multi-frequency ultrasound

Abstract

Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency. However, this has not been well corroborated by the theory. In this paper, a numerical investigation on the inertial cavitation threshold of microbubbles (MBs) under multi-frequency ultrasound irradiation is conducted. The relationships between the cavitation threshold and MB size at various frequencies and in different media are investigated. The results of single-, dual and triple frequency sonication show reduced inertial cavitation thresholds by introducing additional frequencies which is consistent with previous experimental work. In addition, no significant difference is observed between dual frequency sonication with various frequency differences. This study, not only reaffirms the benefit of using multi-frequency ultrasound for various applications, but also provides a possible route for optimizing ultrasound excitations for initiating inertial cavitation.

Multi-frequency sonoreactor characterisation in the frequency domain using a semi-empirical bubbly liquid model

“…There have been an increasing number of studies that reported better results by combining multiple frequencies as opposed to using a single operating frequency [28] , [29] . These findings were further supported by higher cavitation signal measurements found in dual-frequency systems [30] , [31] as well as theoretical studies using simulations of bubbles dynamics [32] , [33] . As research began to focus on the potential of multi-frequency ultrasound in many applications [34] , [35] , [36] , the design of multi-frequency sonoreactors gained interests in recent times.…”

Enhanced HIFU Theranostics with Dual-Frequency-Ring Focused Ultrasound and Activatable Perfluoropentane-Loaded Polymer Nanoparticles

“…Dual-frequency HIFU can effectively activate the phase transition of PFP into microbubbles, significantly reducing the thermal damage threshold of HIFU, enhancing its antitumor efficacy, and realizing ultrasound monitoring imaging. The potential mechanism of dual-frequency-HIFU-enhanced cavitation could be related with bubble dynamics [23]. A dual-frequency approach displays more resonances termed as "combination resonances" and could promote the acoustical scattering cross-section significantly within a much wider range of bubble sizes due to the generation of more resonances [32].…”

“…The gas bubble could either oscillate stably or expand gradually and eventually collapse (stable and inertial cavitation). Cavitation could lead to thermal effects as well as chemical and optical effects [23]. Cavitation-enhanced anti-tumor efficacy mainly results from the enhanced thermal effects and mechanical/chemical effects of cavitation.…”

“…Moreover, HIFU treatment may cause serious complications, such as skin burns and liver and abdominal abscesses due to its high energy output [16][17][18]. Cavitation can enhance the efficacy of HIFU through its thermal [19,20], mechanical [21], and chemical effects [22,23]. Therefore, the synergistic effect of cavitation and HIFU is considered to be a promising way to enhance the therapeutic outcomes.…”

GPU accelerated numerical investigation of the spherical stability of an acoustic cavitation bubble excited by dual-frequency

“…In the last decades, many theories emerged to explain the influence of multiple excitation frequencies, for example, more active zones are generated in the sonochemical reactor [55] , [56] due to the better pattern of the acoustic waves. Others reported the increase of nuclei generated in the bubble cluster [57] , [54] , increased mass transfer via micromixing [58] , the increase of collapse-strength [51] , [59] , [60] , [34] or the lowering of cavitational threshold [61] , [62] . The combination and simultaneous resonance properties of dual-frequency driving can also explain the increased collapse strength [63] .…”