Sophisticated Microbubble Coating Materials for Functional Ultrasound Sensing

Introduction

Lipid-coated microbubbles are fascinating objects rich in nonlinear dynamics. They are used in medicine as ultrasound contrast agents (UCAs) to visualize organ perfusion. The contrast enhancement results from their ultrasound-driven oscillations, which produce a powerful echo.

Sensitivity and Potential

The echo response is sensitive to ambient pressure and the microbubble surroundings, so bubbles have potential sensing capabilities that reach far beyond their current use as contrast agents. However, UCAs contain microbubbles that are non-uniform in size (1-10 μm diameter) and in shell properties. The resulting ill-defined echo inhibits game-changing applications such as non-invasive pressure sensing and molecular sensing using functionalized bubbles that bind to diseased cells.

Microfluidics and Challenges

Microfluidics allows controlled formation of mono-sized bubbles. However, even the echo response of mono-sized bubbles is heterogeneous due to uncontrolled shell properties.

Research Aim

I aim to go beyond size control and enable the microfluidic formation of functional mono-acoustic bubbles with a tuned and predictable acoustic response.

Bridging Disciplines

The challenge is to bridge the gaps between:

1. Fluid dynamics
2. Colloid and interface science
3. Interface rheology
4. Acoustics

This will help unravel the coupled problem of microfluidic bubble-shell formation and ultrasound-driven bubble dynamics in the bulk and near or targeted to a wall.

Methodology

To reach this goal, we will develop highly controlled lab experiments at the sub-microsecond and sub-micrometer level, together with simulations and theory development.

Ultimate Goal

The ultimate goal is a physics-based parametrization of the acoustic bubble response as a function of:

• Shell formulation
• Microfluidic control parameters
• Diffusive gas exchange effects
• Targeted molecular binding of the bubble to a boundary.