Behaviour of Acoustically Levitated Drops in Mid-Water

Area of Science:

• Fluid Dynamics
• Acoustics
• Physical Chemistry

Background:

• Studying liquid drops in liquid-liquid systems is challenging due to instability and difficulty in non-invasive observation.
• Existing methods often lack the precision and long-term stability required for fundamental mechanistic studies.

Purpose of the Study:

• To develop and validate a low-impact acoustic levitation system for immobilised single drops.
• To enable precise, non-invasive, long-term observation of liquid drops for fundamental research.
• To investigate the system's suitability for mass transfer studies and analyze acoustic field effects.

Main Methods:

• Development of a low-impact acoustic levitation apparatus.
• Utilizing non-invasive optical measurements for drop observation.
• Employing rainbow schlieren deflectometry for qualitative analysis of acoustic field effects.

Main Results:

• The system allows for stable levitation and observation of millimetre-sized drops for extended periods (days).
• Precise volume determination, low signal noise, and high reproducibility were achieved.
• No significant acoustic streaming or drop vibration was observed near the levitated drop.
• Acoustic standing wave planes were found to impede the dispersion of dissolved substances.

Conclusions:

• The developed acoustic levitation system provides a robust platform for fundamental research on liquid drops.
• The system is well-suited for mass transfer studies and offers excellent optical accessibility.
• Proper degassing of liquid phases is crucial for system stability and reliable measurements.