Elliptical reflector enhances multi-frequency high-power ultrasound in a thin waveguide

What is it about?

High-power ultrasound plays a critical role in various applications from medical treatment to cleaning and food processing. Yet generating multi-frequency ultrasound in a localized area with a single transducer remains a significant challenge. We propose a transducer with an elliptical surface to excite a metal rod waveguide at multiple frequencies within the megahertz range. A piezoelectric element, which deforms when a voltage is applied, is used as the vibration source. The elliptical surface transforms a plane dilatational wave from the piezoelectric elements into a transverse wave, focused on the thin waveguide using mode conversion. The use of transverse waves reduces energy loss during the reflection process and achieves a smaller focal diameter. Finite element analysis verified wave focusing with the elliptical reflector and the thin waveguide excitation. The fabricated prototype achieved high vibration velocities at the central tip of the waveguide, including 6.7 m/s at 1.767 MHz and 12.8 m/s at 0.411 MHz. At 1.767 MHz, the vibration velocity increased linearly with increasing applied voltage, suggesting the potential for achieving even higher velocities with greater energy input. At 0.411 MHz, the stress within the thin waveguide was expected to exceed the material’s tensile strength, indicating that the design maximized the material’s performance limits.

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Photo by Sime Basioli on Unsplash

Photo by Sime Basioli on Unsplash

Why is it important?

The work is timely because many emerging biomedical and industrial processes—including catheter-based thermal ablation, dual-frequency cavitation, and sonochemistry—now demand localized, multi-frequency acoustic power that currently requires cumbersome arrays of purpose-built transducers. TW-ELIPS collapses that complexity into a single probe, letting researchers sweep or superimpose frequencies streamline experimental set-ups, and push nonlinear ultrasound studies into previously inaccessible regimes. By unlocking efficient, catheter-scale delivery of megahertz-range power across multiple resonances, our platform offers to accelerate discovery in acoustics, expand therapeutic options for minimally-invasive medicine, and open new avenues in process intensification—making the manuscript relevant to a broad readership spanning physics, engineering, and applied life-sciences communities.

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