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Updated: Aug 6, 2026
08:19
Induction of Microstreaming by Nonspherical Bubble Oscillations in an Acoustic Levitation System
Published on: May 9, 2021
Acoustic control of nonspherical shape oscillations in microbubbles using a Koopman linear quadratic regulator
1Mechanical and Aerospace Engineering Department, University of Colorado Colorado Springs, Colorado Springs, Colorado 80918, USA.
The Journal of the Acoustical Society of America
|July 22, 2026
Summary
This study uses Koopman operator theory to control bubble oscillations for medical ultrasound applications. The advanced Koopman linear quadratic regulator (KLQR) controller enables precise manipulation of bubble shapes and rupture times.
Area of Science:
- Acoustic cavitation
- Nonlinear dynamics
- Control theory
Background:
- Large-amplitude bubble oscillations induce destabilizing, nonspherical dynamics.
- Acoustic excitation of microbubbles is relevant for medical applications like ultrasound diagnostics and drug delivery.
- Nonspherical shape oscillations generate significant secondary effects, including microstreaming, jetting, and acoustic backscatter.
Purpose of the Study:
- To actively control bubble shape oscillations using Koopman operator theory.
- To drive bubbles to follow specific harmonic oscillations or controlled rupture dynamics.
- To generalize acoustic control frameworks for flexible target specification.
Main Methods:
- Application of Koopman operator theory to acoustic bubble dynamics.
- Utilizing a modified Koopman linear quadratic regulator (KLQR) controller.
- Defining the KLQR controller using Koopman eigenfunctions based on bubble observables, not just state.
Main Results:
- Demonstrated control of uncoated, nonspherical bubbles.
- Achieved targeted harmonic oscillations at specific frequencies.
- Enabled controlled bubble rupture at a prescribed time.
- Generalized the control framework by using eigenfunctions based on observables.
Conclusions:
- The modified KLQR controller offers a generalized and flexible approach to controlling acoustic bubble dynamics.
- This method has potential applications in medical ultrasound for precise manipulation of bubble behavior.
- Controlling bubble shape oscillations is crucial for optimizing secondary effects in therapeutic and diagnostic ultrasound.
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