Virtual membrane for filtration of particles using surface acoustic waves (SAW)

Area of Science:

• Acoustofluidics
• Biotechnology
• Nanotechnology

Background:

• Surface acoustic wave (SAW) technology offers contactless, non-invasive, and biocompatible particle manipulation.
• Existing methods for particle separation can be limited in sensitivity and throughput for biological applications.

Purpose of the Study:

• To develop a sensitive particle sorting system based on SAW for size-selective filtration.
• To demonstrate the efficacy of the 'virtual membrane' concept for separating particles of different sizes.

Main Methods:

• Utilized a periodic acoustic field generated by focused interdigital transducers (FIDTs) to create a standing SAW.
• Implemented a 'virtual membrane' where particles larger than ~0.3 times the acoustic half-wavelength are repelled by acoustic forces.
• Applied varying acoustic power and flow rates to achieve size-selective filtration of polystyrene particles.

Main Results:

• Demonstrated high size selectivity in particle filtration using the virtual membrane.
• Successfully filtered 8 μm particles from 5 μm particles.
• Separated 10.36 μm particles from 7.0 μm and 5.0 μm particles at high frequencies (258 MHz, 192.5 MHz, 129.5 MHz).

Conclusions:

• The virtual membrane approach using SAW provides an effective method for size-selective particle filtration.
• The system operates at low power (10s of mW) and accommodates microfluidic flow rates (μl min⁻¹).
• This technology holds promise for advanced biological studies and diagnostic applications requiring precise particle separation.