On-chip particle levitation and micromanipulation using bulk acoustic waves.

Area of Science:

• Acoustofluidics
• Biomedical Engineering
• Microfluidics

Background:

• Acoustofluidics uses sound waves for microscale manipulation in fluids.
• Surface acoustic wave devices have limitations in workspace.
• Existing planar transducer configurations restrict manipulation near microchannel surfaces.

Purpose of the Study:

• To present a novel 3D acoustofluidic platform utilizing a digitally addressable array of piezoelectric micromachined ultrasound transducers (PMUTs).
• To generate and characterize bulk acoustic waves and acoustic traps within 3D fluidic chambers.
• To demonstrate deterministic 3D levitation and transport of microparticles.

Main Methods:

• Utilized finite element modeling and experimental measurements to quantify acoustic field distribution.
• Investigated acoustic trap formation dynamics.
• Employed spatiotemporal modulation of the acoustic field for particle manipulation.

Main Results:

• Demonstrated deterministic 3D levitation of 30 μm polystyrene particles up to 640 μm above the surface with <6% positional error.
• Achieved stable particle trapping under continuous flow (up to 40 μL min⁻¹) using acoustic radiation forces up to 90 pN.
• Showcased continuous planar transport of microparticle aggregates via acoustic field modulation.

Conclusions:

• The developed PMUT-based acoustofluidic platform enables precise 3D micromanipulation in fluidic chambers.
• The system is scalable and readily integrable with compact fluidic systems using standard microfabrication techniques.
• This work provides a foundation for reconfigurable and advanced acoustofluidic micromanipulation systems for lab-on-chip applications.