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Published on: May 9, 2021
Enhancing subharmonic response by controlling initial state of monodisperse microbubbles via a multi-gas core
Sihan Chen1, Chang Lu1, Hongyi Zhang1
1School of Automation and Intelligent Sensing, Shanghai Jiao Tong University, Shanghai 200240, China.
Ultrasonics Sonochemistry
|July 11, 2026
Summary
Increasing carbon dioxide in microbubbles enhances their subharmonic response for ultrasound applications. This finding improves nonlinear imaging and blood pressure estimation by tuning microbubble states.
Area of Science:
- Acoustics and Biomedical Engineering
- Microfluidics and Materials Science
Background:
- Microbubbles are crucial for nonlinear ultrasound imaging and non-invasive blood pressure estimation.
- Understanding microbubble subharmonic response mechanisms is key to advancing these ultrasound applications.
Purpose of the Study:
- To investigate how varying CO2 fractions in multi-gas core microbubbles affect their initial state and subharmonic response.
- To elucidate the mechanisms governing enhanced subharmonic generation in microbubbles.
Main Methods:
- Fabrication of monodisperse microbubbles (MDMBs) with controlled CO2 fractions (0-80%) using a flow-focusing microfluidic device.
- Characterization of bubble states (elastic, buckling transition, buckling) using pressure-dependent attenuation spectra and resonance frequency curves.
- Statistical analysis of subharmonic generation threshold and amplitude in relation to bubble state.
Main Results:
- Increasing CO2 fraction shifted MDMBs from elastic to buckling transition states, decreasing surface tension and increasing shell elasticity.
- MDMBs closer to the buckling state showed a ~12% lower threshold for subharmonic generation and an ~11 dB higher subharmonic amplitude.
- Controlled tuning of MDMB initial state via CO2 fraction directly enhances subharmonic response.
Conclusions:
- The initial state of microbubbles, particularly approaching buckling, is the primary mechanism for enhanced subharmonic response.
- Findings support nonlinear bubble oscillation theory and provide a method for tailoring microbubble properties for improved ultrasound applications.
- This research offers a pathway to optimize microbubbles for advanced medical ultrasound technologies.
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