Power Ultrasound: Mechanisms & Applications

• Power ultrasound is the use of high-intensity acoustic waves to induce cavitation, radiation forces, and nonlinear effects in various media.
• It leverages controlled energy deposition—from low-frequency cavitation in liquids to MHz resonant bioeffects—to enable applications in materials processing, biomedical therapy, and power transfer.
• Its applications span scaffold modification, battery recycling, tissue treatment, and wireless power transfer, highlighting design trade-offs and engineering challenges.

Searching arXiv for recent and directly relevant papers on power ultrasound and closely related ultrasonic power-processing/use cases. Power ultrasound (PUS) denotes ultrasonic operation in regimes where acoustic power and intensity are sufficient to produce significant mechanical, thermal, or energetic effects rather than solely sensing or imaging. Across the literature represented here, PUS spans low-frequency cavitation-driven processing in liquids and porous solids, high-intensity focused ultrasound (HIFU) for wireless acoustic power transfer, MHz-range standing-wave systems that induce reversible membrane permeabilization without cavitation, and power-law acoustic models needed to predict attenuation, backscatter, dispersion, and heating in tissue [(Watson et al., 2013); (Bhargava et al., 2020); (Nandy et al., 4 Mar 2026); (Parker, 2022)]. A unifying feature is that ultrasound is treated as an actuator of material change, energy delivery, or controlled bioeffect. The physical mechanisms, however, vary sharply with frequency, intensity, medium, and device architecture: inertial cavitation and microstreaming dominate classical kHz sonoprocessing, whereas radiation forces, standing-wave potentials, viscoelastic dissipation, and frequency-dependent absorption become central in MHz biomedical and power-transfer settings [(Watson et al., 2013); (Nandy et al., 4 Mar 2026); (Bhargava et al., 2020)].

1. Definition, operating regimes, and conceptual scope

In the sonochemical and processing literature, power ultrasound is conventionally associated with frequencies above $20~\mathrm{kHz}$ and powers typically $50~\mathrm{W}$ and above, with the explicit goal of producing strong cavitation and associated mechanical effects in a liquid medium (Watson et al., 2013). In medical and energetic contexts, the same term extends to applications where ultrasound acts primarily as a carrier of energy rather than an imaging signal, including HIFU, ultrasonic power transfer, thrombolytic or ablative ultrasound, and acoustically driven elastography (Parker, 2022, Narvaez et al., 2021, Bhargava et al., 2020). Some recent work also defines a controlled, cavitation-free branch of PUS in which deterministic radiation forces, streaming, and membrane stresses are used to induce reversible bioeffects in microfluidic systems (Nandy et al., 4 Mar 2026).

The governing distinction from diagnostic ultrasound is functional. Diagnostic systems are designed for information extraction under exposure limits intended to avoid substantial mechanical or thermal perturbation, whereas PUS systems are designed to deposit energy, induce stress, alter transport, or trigger structural change (Narvaez et al., 2021, Bhargava et al., 2020). In low-frequency liquids and soft matter, this usually implies cavitation, microjets, microstreaming, shock waves, and heating [(Watson et al., 2013); (Li et al., 5 Dec 2025); (Chaigne et al., 2 Sep 2025)]. In focused or resonant MHz systems, the relevant effects include concentrated acoustic intensity, nonlinear harmonic generation, viscoelastic dissipation, radiation force, and frequency-dependent absorption in tissue or fluid (Bhargava et al., 2020, Bhargava et al., 2020, Parker, 2022).

The literature represented here also shows that “power” need not imply violent cavitation in every case. Antibubble payload-release systems, for example, are explicitly positioned below classical PUS conditions: they respond at kPa-level acoustic pressures and equivalent plane-wave intensities well below typical high-intensity thresholds, yet exploit engineered inclusions to obtain a localized nonlinear response (Moreno-Gomez et al., 2023). This suggests a useful distinction between classical PUS, where the bulk medium is driven into a strongly nonlinear regime, and engineered low-threshold ultrasound-responsive systems, where the medium remains near linear acoustics while embedded structures convert modest fields into large local effects. That implication follows the authors’ framing of antibubbles as a route to avoid collateral effects normally associated with high-power insonification (Moreno-Gomez et al., 2023).

2. Core physical mechanisms

In classical low-frequency PUS, acoustic cavitation is the central mechanism. Cavitating bubbles grow and collapse under the applied field, producing high local pressures and temperatures, microjets, and intense microstreaming. In porous polymer scaffolds, these effects are invoked to “punch holes” in pore walls, remove obstructions, and promote pore interconnectivity and fluid transport (Watson et al., 2013). In tube-transducer sonoprocessing for battery-anode recycling, cavitation manifests as dense bubble clouds, filamentary bubble structures, shock-wave and jetting effects, sonochemiluminescence, and direct erosion or puncturing of metal-supported coatings (Li et al., 5 Dec 2025). In early-age cement paste, cavitation, streaming, and local heating are proposed to disturb early hydration products, create micro-cracks, and increase porosity, thereby degrading later micromechanical properties (Chaigne et al., 2 Sep 2025).

In focused power-transfer systems, nonlinear propagation and resonance become central. HIFU-based ultrasonic power transfer uses focused fields to reduce spreading losses and maximize energy at a compact piezoelectric receiver. The relevant physical chain includes transmitter vibration, nonlinear acoustic propagation through a medium, acoustic-structure interaction at the receiver, and piezoelectric conversion to electrical power (Bhargava et al., 2020, Bhargava et al., 2020). In these systems, increasing source strength drives harmonic generation, waveform distortion, and acoustic saturation. One consequence is that energy migrates from the fundamental frequency into harmonics that a single-frequency receiver may not efficiently harvest, reducing transfer efficiency and shifting the location of maximum harvested output away from the geometric focus and toward the source (Bhargava et al., 2020). A related but distinct mechanism appears in acoustic-electroelastic modeling of piezoelectric disks: if higher harmonics generated by nonlinear propagation coincide with structural resonances of the receiver, then disproportionately large electrical responses can occur (Bhargava et al., 2020).

In cavitation-free MHz microacoustofluidic PUS, the mechanism is deterministic membrane stressing by acoustic radiation force, acoustic streaming, hydrodynamic drag, and hydrodynamic interactions within cell clusters. In Programmable Acoustic Standing-wave Transfection, these stresses are accumulated over programmable frequency sweeps to raise membrane tension into a regime where reversible pores form, enhancing transport of biomolecules without chemical carriers or contrast agents (Nandy et al., 4 Mar 2026). The paper gives explicit scaling relations in which radiation and streaming stresses scale with $V_{p-p}^2$, while acoustophoretic migration and interaction stresses scale with $V_{p-p}^3$, thereby linking device power directly to membrane energetics and effective diffusivity (Nandy et al., 4 Mar 2026).

A further mechanism important in medical PUS is frequency-dependent attenuation and dispersion. Tissue attenuation is described as a power law,

$\alpha(f)=\alpha_0 f^{a_1},$

with $a_1 \approx 1$ for soft vascularized tissues over typical diagnostic bands, and a representative magnitude $\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$ (Parker, 2022). The corresponding intensity decay with depth,

$$I(x,f)=I_0 e^{-2\alpha(f)x}=I_0\exp\big(-2\alpha_0 f^{a_1}x\big),$$

directly controls energy deposition and heating in HIFU-like regimes (Parker, 2022). This makes power-law acoustics foundational to predictive PUS simulation even when the immediate application lies outside diagnostic ultrasound.

3. Device classes and system architectures

The literature covers several distinct PUS source architectures. The probe sonicator is the canonical low-frequency configuration. In scaffold post-processing, a Hielscher UP100 probe sonicator is used in water or ethanol, with mild operation at $20~\mathrm{W}$, 20% duty cycle, and extreme operation at $100~\mathrm{W}$, 100% duty cycle (Watson et al., 2013). The sonotrode is positioned about $50~\mathrm{W}$0 above the scaffold in a test tube, with the sample cooled in a $50~\mathrm{W}$1 water bath to avoid exceeding the polymer glass transition temperature (Watson et al., 2013). This architecture is designed for strong local cavitation in confined liquid volumes.

The Langevin horn or sonotrode appears again in battery-recycling sonoprocessing, where a $50~\mathrm{W}$2 horn is compared against a radially poled tubular piezoceramic source (Li et al., 5 Dec 2025). The horn produces the familiar conical cavitation cloud concentrated beneath the tip, while the tube transducer generates cavitation distributed throughout its bore with peak activity on the central axis (Li et al., 5 Dec 2025). This device comparison is important because it reframes a standard PUS engineering trade-off: conventional horns deliver high local intensity but poor bulk coverage, whereas bath transducers treat larger volumes at lower intensity. The tube transducer is presented as a geometry that combines sonotrode-like intensity with volumetric distribution, which suggests promise for high-throughput flow-based sonochemistry and sonoprocessing (Li et al., 5 Dec 2025).

Focused biomedical and power-transfer systems rely on different architectures. One class uses single-element HIFU transducers operating around $50~\mathrm{W}$3, together with finite-size piezoelectric disk receivers tuned near the same frequency (Bhargava et al., 2020, Bhargava et al., 2020). Another class uses piezoelectric micromachined ultrasonic transducers (PMUTs). In a wireless brain-implant powering study, a $50~\mathrm{W}$4 PMUT array occupying $50~\mathrm{W}$5 is designed to resonate at $50~\mathrm{W}$6, with a maximum on-axis acoustic intensity of $50~\mathrm{W}$7 at a depth of about $50~\mathrm{W}$8 in the near field for a drive voltage of $50~\mathrm{W}$9 (Narvaez et al., 2021). The design is based on equivalent-circuit models, fluid loading, mutual impedance analysis, and Rayleigh-distance considerations (Narvaez et al., 2021). Although this is a power-transfer rather than a therapeutic system, it clearly falls under PUS because the design objective is maximum safe acoustic energy delivery, not imaging (Narvaez et al., 2021).

Recent work also broadens PUS hardware beyond phased arrays and rigid lenses. A dynamic microfluidic lens with two orthogonal channel layers implements binary phase modulation through selective filling with liquids of different sound speeds, providing 400 addressable pixels using 80 pumps and approximately one-second reconfiguration time (Zhang et al., 7 Jul 2026). The system is explicitly designed for stable performance under high acoustic power and is demonstrated for dynamic heating and particle manipulation with a 1 MHz HIFU-type source (Zhang et al., 7 Jul 2026). In air, mechanically translated amplitude masks over a non-uniform ultrasound source enable reconfigurable intense midair fields at $V_{p-p}^2$0, supporting radiation-force-driven bead manipulation and suggesting room-scale PUS applications such as haptics and levitation (Hasegawa, 21 Mar 2025).

4. PUS in materials processing and sonoprocessing

Materials processing is one of the clearest manifestations of classical PUS. In polymer scaffold post-processing, high-power ultrasound is applied to supercritical-$V_{p-p}^2$1-foamed PLA scaffolds to increase pore interconnectivity, pore size, and fluid transport (Watson et al., 2013). The scaffold filling fraction is defined by

$V_{p-p}^2$2

with explicit mass–volume formulas used to infer liquid uptake from gravimetric measurements (Watson et al., 2013). Quantitatively, water immersion without ultrasound saturates at $V_{p-p}^2$3, mild sonication in water gives $V_{p-p}^2$4, extreme sonication in water yields $V_{p-p}^2$5, and the mild-with-prewetting protocol reaches $V_{p-p}^2$6, כלומר essentially full saturation within error (Watson et al., 2013). Mean pore diameter increases from $V_{p-p}^2$7 to $V_{p-p}^2$8 under mild-with-prewetting and from $V_{p-p}^2$9 to $V_{p-p}^3$0 under extreme sonication, while mass loss remains small at about 0.6% and 1.9%, respectively (Watson et al., 2013). These results establish PUS as a selective microstructural post-processing tool in thick foams rather than merely a surface treatment.

In lithium-ion battery anode recycling, the goal is delamination of graphite coatings from copper foil using cavitation-intensive PUS (Li et al., 5 Dec 2025). The tube transducer operates at $V_{p-p}^3$1 with input powers of $V_{p-p}^3$2 and $V_{p-p}^3$3, while the sonotrode operates at $V_{p-p}^3$4 and $V_{p-p}^3$5 (Li et al., 5 Dec 2025). Sonochemiluminescence and high-speed imaging show that the tube generates cavitation as intense as or more intense than the sonotrode, but distributed throughout the bore rather than localized beneath a tip (Li et al., 5 Dec 2025). For a $V_{p-p}^3$6 effective flake loading, the sonotrode leaves 94%, 89%, and 72% remaining mass depending on tip position, whereas the tube leaves 23% remaining mass at both $V_{p-p}^3$7 and $V_{p-p}^3$8, which is the theoretical residual corresponding to complete coating removal (Li et al., 5 Dec 2025). At $V_{p-p}^3$9, the tube can fully delaminate up to $\alpha(f)=\alpha_0 f^{a_1},$0 of original anode area in 2 s; above that threshold, remaining mass increases, indicating overloading (Li et al., 5 Dec 2025). This provides a concrete scale for high-throughput PUS reactor design.

Power ultrasound can also alter the mechanics of soft condensed matter. In carbon black colloidal gels, high-power ultrasound at $\alpha(f)=\alpha_0 f^{a_1},$1 and pressures above a threshold $\alpha(f)=\alpha_0 f^{a_1},$2 induces a transient decrease in storage modulus, a strong overshoot in loss modulus, a reduction in yield strain, and facilitated flow at low imposed shear rates (Dagès et al., 2020). Time-resolved ultrasmall-angle X-ray scattering indicates intermittent micro-crack formation in the bulk gel, while the small-scale fractal aggregates remain intact (Dagès et al., 2020). The authors interpret the rheological softening and enhanced dissipation in terms of dynamic crack opening and closure, which is a markedly different PUS effect from cavitation-induced erosion yet still reflects ultrasound-driven mesoscale structural damage (Dagès et al., 2020).

A closely related but reactive system is early-age cement paste. Probe-based PUS at $\alpha(f)=\alpha_0 f^{a_1},$3, amplitudes up to $\alpha(f)=\alpha_0 f^{a_1},$4, and exposures up to 4 min alters the later micromechanical properties of hardened paste (Chaigne et al., 2 Sep 2025). Micro-indentation hardness, indentation modulus, and creep modulus all decrease monotonically with a normalized energy index proportional to

$\alpha(f)=\alpha_0 f^{a_1},$5

while nano-indentation indicates that the intrinsic properties of low-density and high-density C–S–H phases remain largely unchanged (Chaigne et al., 2 Sep 2025). Increased acoustic emission during micro-scratch testing supports the interpretation that PUS raises porosity and micro-crack density rather than modifying nanoscale C–S–H stiffness (Chaigne et al., 2 Sep 2025). This suggests that, in reactive colloidal gels, PUS can tune mesoscopic compliance and ductility through damage mechanisms even when the nanophase remains essentially constant.

5. Biomedical and energetic applications

Biomedical PUS includes both direct therapeutic action and indirect support functions such as monitoring, tissue characterization, and wireless power transfer. In medical tissue, the importance of power-law attenuation is immediate. With

$\alpha(f)=\alpha_0 f^{a_1},$6

lower frequencies penetrate deeper and distribute heating more broadly, whereas higher frequencies concentrate heating nearer the focus but increase near-field thermal risk (Parker, 2022). The same framework links attenuation, backscatter, speckle, sound speed, and shear-wave dispersion to a multiscale, fractal-like tissue architecture, and the review explicitly argues that this unified view is useful for treatment planning, monitoring, and tissue characterization in power-ultrasound contexts (Parker, 2022).

Wireless ultrasonic power transfer is a particularly clear energetic application. In the PMUT-based brain-implant system, the transmitter is a $\alpha(f)=\alpha_0 f^{a_1},$7 array designed for near-field operation in the mouse brain, delivering a simulated maximum acoustic intensity of $\alpha(f)=\alpha_0 f^{a_1},$8 at $\alpha(f)=\alpha_0 f^{a_1},$9 depth with a $a_1 \approx 1$0 drive, close to the stated FDA-recommended limit of $a_1 \approx 1$1 time-averaged intensity (Narvaez et al., 2021). The work emphasizes electromechanical coupling, array geometry, mutual impedance, and safe operation rather than imaging metrics, which situates it firmly within PUS engineering (Narvaez et al., 2021).

The HIFU-based power-transfer literature adds a nonlinear perspective. In focused acoustic power transfer at $a_1 \approx 1$2, increasing drive amplitude reduces efficiency as nonlinear propagation transfers energy from the fundamental to higher harmonics, to which the piezoelectric receiver is comparatively insensitive (Bhargava et al., 2020). The maximum voltage output position shifts upstream from the geometric focus as source strength rises, because the spatial distribution of the fundamental component changes under nonlinear propagation (Bhargava et al., 2020). A companion acoustic-electroelastic study shows that if acoustic harmonics coincide with structural resonances of the receiver disk, the output can increase dramatically; a tuned multi-harmonic excitation yields about 75% more average power than a purely fundamental excitation at the same total source energy (Bhargava et al., 2020). Together these papers show that PUS in power-transfer systems is fundamentally a coupled nonlinear-acoustics and structural-resonance problem.

Not all biomedical uses of ultrasound energy operate in classical high-power regimes. Antibubble-based payload release is deliberately designed for low-intensity ultrasound response. At 1 MHz, release thresholds can be below $a_1 \approx 1$3 for $a_1 \approx 1$4 hydrophilic antibubbles, $a_1 \approx 1$5 for $a_1 \approx 1$6 hydrophobic antibubbles, and $a_1 \approx 1$7 for $a_1 \approx 1$8 hydrophilic antibubbles, corresponding to equivalent plane-wave intensities from about $a_1 \approx 1$9 to $\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$0 (Moreno-Gomez et al., 2023). The background medium remains in a linear-acoustics regime, yet the inclusions undergo catastrophic collapse, transient bridging, or multi-pulse release (Moreno-Gomez et al., 2023). This does not fit the classical cavitation-based definition of PUS, but it is directly relevant to how acoustic energy can be engineered to produce strong local actuation without global high-intensity exposure.

Another nonclassical biomedical example is Programmable Acoustic Standing-wave Transfection. The device operates at 0.900–1.200 MHz with key resonance at $\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$1, electrical input powers from 1.2 W to 5.0 W, and a duty-cycled protocol of $\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$2, $\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$3 (Nandy et al., 4 Mar 2026). At 2.0 W, the method induces robust reversible transport of dyes and doxorubicin with high viability, while at 3.2 W heating becomes significant, about $\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$4 per 30 s actuation window (Nandy et al., 4 Mar 2026). The system is explicitly described as operating in the PUS regime but in a cavitation-free manner, making it a model of deterministic mechanoporation rather than stochastic bubble-mediated sonoporation (Nandy et al., 4 Mar 2026).

6. Modeling, scaling laws, and design constraints

Power-ultrasound design depends strongly on quantitative models. In tissue, the central frequency-dependent relations include longitudinal attenuation,

$\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$5

backscatter,

$\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$6

phase speed,

$\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$7

and shear-wave constitutive behavior,

$\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$8

with shear-wave speed approximately obeying a power law in frequency when the fractional term dominates (Parker, 2022). These are not merely diagnostic descriptors. They determine penetration depth, focal confinement, heating, lesion geometry, elastographic response, and the interpretation of monitoring signals during therapy (Parker, 2022).

For numerical treatment of power-law absorption, a 2024 paper introduces a time-fractional, static-memory, Fourier pseudo-spectral method intended to model frequency-dependent power-law absorption in tissue (King et al., 2024). The supplied data explicitly note that the available source text is a template rather than the scientific article, so the detailed equations and results are not recoverable from the provided material (King et al., 2024). It is nevertheless explicitly stated that the method is motivated by first-order linear wave equations with fractional-time loss, offers fixed memory cost irrespective of the number of time steps, and has the advantage of a local treatment of the power law, enabling a spatially varying frequency power-law (King et al., 2024). This suggests direct relevance for heterogeneous-tissue PUS simulation, though any stronger technical claim would exceed the provided evidence.

In airborne or free-space PUS, field synthesis becomes a diffraction and aperture-shaping problem. The 2025 amplitude-mask method for intense midair ultrasound represents the field using the Rayleigh–Sommerfeld integral

$\alpha_0 \approx 0.05~\mathrm{Np/cm\text{-}MHz}$9

and designs a binary mask by a least-squares criterion over translated source–mask alignments (Hasegawa, 21 Mar 2025). The time-averaged intensity in a harmonic lossless medium is

$$I(x,f)=I_0 e^{-2\alpha(f)x}=I_0\exp\big(-2\alpha_0 f^{a_1}x\big),$$0

which is the same basic energetic metric that governs force and heating elsewhere in PUS, albeit in an airborne regime at $$I(x,f)=I_0 e^{-2\alpha(f)x}=I_0\exp\big(-2\alpha_0 f^{a_1}x\big),$$1 (Hasegawa, 21 Mar 2025).

At the system level, power and duty-cycle management can itself become a central design variable. A wearable ultrasound system for long-term muscle monitoring uses sEMG to trigger diagnostic A-mode acquisition only during activity, reducing average power to $$I(x,f)=I_0 e^{-2\alpha(f)x}=I_0\exp\big(-2\alpha_0 f^{a_1}x\big),$$2 for a 200 ms contraction at 1 Hz and achieving more than 59% energy savings relative to continuous operation (Frey et al., 2023). This is not power ultrasound in the therapeutic sense, but it provides a general systems insight: average power in ultrasonic devices often scales as a baseline plus an active-mode increment times duty cycle. That principle is directly transferable to pulsed PUS systems where exposure windows and thermal recovery matter.

7. Controversies, trade-offs, and open questions

The PUS literature is marked by strong trade-offs rather than a single directional trend. In scaffold modification, mild ultrasound with ethanol prewetting outperforms extreme continuous water sonication, giving larger pore growth, full saturation, and lower mass loss (Watson et al., 2013). In cement paste, high-power probe sonication degrades later micromechanical properties rather than improving them, despite earlier reports in other cementitious contexts of strength enhancement under different power and geometry conditions (Chaigne et al., 2 Sep 2025). In carbon black gels, ultrasound softens the material and facilitates flow through micro-crack formation, but the same mechanism implies internal damage and structural heterogeneity (Dagès et al., 2020). These examples show that increased acoustic energy does not map monotonically to desirable processing outcomes.

In energetic transfer systems, stronger focusing or higher source drive can reduce rather than improve effective power delivery. Nonlinear propagation in HIFU-based power transfer shifts energy to harmonics and moves the best receiver position away from the geometric focus (Bhargava et al., 2020). Yet the acoustic-electroelastic study indicates that harmonics can be beneficial if receiver modal structure is deliberately matched (Bhargava et al., 2020). This is less a contradiction than a design constraint: nonlinear propagation is advantageous only when the receiver and circuit architecture are co-designed to exploit the altered spectrum.

In biomedical delivery, there is an ongoing distinction between cavitation-mediated and non-cavitational mechanisms. Antibubble systems and PAST both aim to circumvent the unpredictability and collateral damage associated with classical high-power cavitation, yet they do so differently: one engineers gas-shell inclusions to respond at very low intensities, while the other uses standing-wave radiation forces and streaming to permeabilize membranes reversibly (Moreno-Gomez et al., 2023, Nandy et al., 4 Mar 2026). A plausible implication is that future biomedical PUS may bifurcate into two engineering traditions: one centered on controlled cavitation nuclei and one centered on programmable non-cavitational stress fields.

Another unresolved issue is scale-up. The tube transducer for battery recycling suggests a path toward high-throughput flow-based reactors, but its industrial viability depends on numbering-up, residence-time control, and long-term transducer robustness under cavitation (Li et al., 5 Dec 2025). The microfluidic lens platform offers a different route to large-area, high-power field shaping with hardware complexity scaling as the square root of pixel count, yet reconfiguration is limited to about one second and binary phase states (Zhang et al., 7 Jul 2026). These approaches address different bottlenecks—volumetric cavitation coverage versus programmable focal control—and may prove complementary rather than competitive.

Finally, the tissue-acoustics perspective emphasizes that PUS models are only valid over finite bands. The power-law review explicitly notes robustness for longitudinal waves in 2–20 MHz soft vascularized tissues and for shear waves in 50–500 Hz elastography, with likely breakdown at very low or very high frequencies and in anisotropic or highly ordered tissues (Parker, 2022). This places a methodological constraint on extrapolating power-law-based treatment planning outside validated spectral regimes.

8. Synthesis

Across biomedical engineering, soft matter, porous materials, sonochemistry, and acoustic power transfer, power ultrasound is best understood not as a single technique but as a family of energy-delivery modalities coupled to medium-specific mechanisms. In low-frequency liquids and porous solids, PUS is predominantly a cavitation technology, generating microjets, shock waves, erosion, radical chemistry, and streaming that can open scaffold pores, delaminate battery coatings, or damage early-age cement networks [(Watson et al., 2013); (Li et al., 5 Dec 2025); (Chaigne et al., 2 Sep 2025)]. In focused MHz systems, it is a wave-propagation and resonance technology, where attenuation, nonlinear harmonics, and acoustic-structure interaction determine energy-transfer efficiency and bioeffect localization (Bhargava et al., 2020, Bhargava et al., 2020, Narvaez et al., 2021). In microacoustofluidic and responsive-material platforms, it becomes a means of programmable force generation, controlled membrane stressing, or thresholded release at substantially lower intensities than classical cavitation-based processing (Nandy et al., 4 Mar 2026, Moreno-Gomez et al., 2023).

The cross-cutting technical lesson is that PUS performance is governed by multiscale coupling: transducer architecture, field distribution, frequency-dependent absorption, microstructural susceptibility, and temporal duty cycle all matter simultaneously. The power-law framework for tissue acoustics supplies a unifying physical basis for medical PUS prediction (Parker, 2022). Equivalent-circuit and acoustic-structure models are indispensable for energetic transfer devices (Narvaez et al., 2021, Bhargava et al., 2020). Cavitation mapping and sonochemiluminescence remain essential for reactor-scale sonoprocessing (Li et al., 5 Dec 2025). And where control rather than brute intensity is the goal, programmable standing waves, binary phase lenses, and engineered responsive inclusions suggest new PUS paradigms that reduce reliance on uniformly high exposure (Nandy et al., 4 Mar 2026, Zhang et al., 7 Jul 2026, Moreno-Gomez et al., 2023).

Power ultrasound, in that broader sense, is the deliberate use of ultrasound as an instrument of work: to reshape matter, deposit energy, drive transport, or reconfigure microstructure. The diversity of the cited work shows that its future lies as much in precise field design and mechanistic selectivity as in raw acoustic power.