Microfluidic acoustic sawtooth metasurfaces for patterning and separation using traveling surface acoustic waves

Area of Science:

• Acoustofluidics
• Metasurfaces
• Microfluidics

Background:

• Microfluidic devices are crucial for manipulating small volumes of fluids and particles.
• Controlling acoustic fields is essential for various acoustofluidic applications.
• Existing methods often require complex setups or multiple acoustic waves.

Purpose of the Study:

• To introduce a novel sawtooth-based metasurface for flexible acoustic field orientation in microfluidics.
• To demonstrate arbitrary steering of acoustic fringes using sub-wavelength channel features.
• To offer a simpler, single-travelling-wave acoustofluidic approach.

Main Methods:

• Fabrication of a polydimethylsiloxane (PDMS) metasurface with sawtooth features.
• Integration of the metasurface into a microfluidic device.
• Generation of acoustic fields using a single surface acoustic wave (SAW).
• Observation of steerable acoustic fringe patterns within the microchannel.

Main Results:

• Successfully demonstrated flexible orientation of acoustic fields via metasurface design.
• Achieved arbitrary steering of acoustic fringes using sub-wavelength channel features.
• Decoupled the fluidic pressure field from the microchannel's shape.
• Showcased steerable pressure fields as a function of the PDMS metasurface's geometry.

Conclusions:

• The sawtooth-based metasurface offers a versatile approach for acoustic field manipulation in microfluidics.
• This method simplifies acoustofluidic device design by using a single SAW and a PDMS metasurface.
• The technique is applicable to microfluidic applications such as patterning, concentration, focusing, and separation of microparticles and cells.