Comparison of Acoustic Streaming Flow Patterns Induced by Solid, Liquid and Gas Obstructions

Area of Science:

• Acoustofluidics
• Microfluidics
• Fluid Dynamics

Background:

• Acoustic streaming is a phenomenon used in microfluidic devices for fluid manipulation.
• Obstructions within micro-channels can influence acoustic streaming patterns.
• Understanding these influences is key to optimizing acoustofluidic device design.

Purpose of the Study:

• To experimentally and numerically compare acoustic streaming induced by gaseous bubbles, liquid droplets, and solid bulges in micro-channels.
• To identify the obstruction type that most efficiently generates strong streaming flows.
• To provide insights for energy-efficient acoustofluidic device design.

Main Methods:

• Micro-channels fabricated using poly(dimethylsiloxane) (PDMS) via soft lithography.
• Experimental investigation using particle tracking velocimetry (PTV).
• Numerical simulation using the finite element method (FEM).

Main Results:

• All obstruction types generated counter-rotating vortical patterns.
• Gaseous bubbles induced the strongest streaming flow (max 21 mm/s).
• Liquid droplets showed the most efficient oscillation transfer, resulting in the largest streaming flow region and average speed, due to higher density and incompressibility.

Conclusions:

• Interfacial conditions at the obstruction boundary significantly affect induced streaming.
• Liquid droplet obstructions are more efficient for generating strong acoustic streaming flows.
• Designing acoustofluidic devices with liquid droplet obstructions may offer improved energy efficiency.