Microfluidic flow switching via localized acoustic streaming controlled by surface acoustic waves

Area of Science:

• Fluid dynamics
• Microfluidics
• Acoustic manipulation

Background:

• Microfluidic devices enable precise control of small fluid volumes.
• Controlling fluid streams within microchannels is crucial for various applications.
• Existing methods often require complex mechanical components.

Purpose of the Study:

• To propose and demonstrate a novel acoustic flow switching device.
• To investigate the mechanism of flow switching induced by surface acoustic waves (SAWs).
• To achieve controlled manipulation of immiscible fluid streams in a microfluidic H-shaped junction.

Main Methods:

• Fabrication of a microfluidic device with a piezoelectric substrate and polydimethylsiloxane (PDMS) microchannel.
• Generation of high-frequency surface acoustic waves (SAWs) using a slanted-finger interdigitated transducer.
• Observation and analysis of acoustic streaming flow and its effect on fluid streams at varying input voltages and flow rates.

Main Results:

• Surface acoustic waves induced acoustic streaming flow with symmetrical microvortices.
• The acoustic streaming flow successfully switched the paths of two immiscible fluid streams.
• On-demand flow switching was achieved by tuning input voltage and flow rates without mechanical actuators.

Conclusions:

• The proposed acoustic flow switching device offers a precise and controllable method for fluid manipulation in microfluidics.
• This SAW-based technique eliminates the need for internal moving parts, simplifying device design.
• The technology holds potential for integration into complex experimental platforms for lab-on-a-chip applications.