Near-field acoustic imaging with a caged bubble

TL;DR

This paper introduces a novel method using a caged bubble as a local probe for near-field acoustic imaging, achieving high resolution and enabling new applications in acoustic microscopy.

Contribution

It demonstrates the use of a 3D-printed caged bubble to perform near-field acoustic microscopy, allowing high-resolution imaging of complex structures at the single-bubble level.

Findings

Achieved imaging resolution two orders of magnitude smaller than the acoustic wavelength.

Successfully demonstrated near-field imaging of complex structures.

Proposed a low-cost approach for acoustic microscopy using caged bubbles.

Abstract

Bubbles are ubiquitous in many research applications ranging from ultrasound imaging and drug delivery to the understanding of volcanic eruptions and water circulation in vascular plants. From an acoustic perspective, bubbles are resonant scatterers with remarkable properties, including a large scattering cross-section and strongly sub-wavelength dimensions. While it is known that the resonance properties of bubbles depend on their local environment, it remains challenging to probe this interaction at the single-bubble level due to the difficulty of manipulating a single resonating bubble in a liquid. Here, we confine a cubic bubble inside a cage using 3D printing technology, and we use this bubble as a local probe to perform scanning near-field acoustic microscopy -- an acoustic analogue of scanning near-field optical microscopy. By probing the acoustic interaction between a single resonating bubble and its local environment, we demonstrate near-field imaging of complex structures with a resolution that is two orders of magnitudes smaller than the wavelength of the acoustic field. As a potential application, our approach paves the way for the development of low-cost acoustic microscopes based on caged bubbles.