Acoustic Nanoparticle Trapping Is Driven by Synergy between Acoustic and Hydrodynamic Interactions

Area of Science:

• Microfluidics
• Acoustic manipulation
• Nanoparticle handling

Background:

• Acoustic forces in resonant microfluidic chambers enable micrometer-sized particle manipulation.
• Nanoparticle trapping has been previously achieved at high concentrations or with pre-seeded chambers.

Purpose of the Study:

• To elucidate the trapping mechanism of nanoparticles in microfluidic chambers.
• To investigate the role of acoustic forces and hydrodynamic interactions in particle trapping.
• To explore density-selective nanoparticle trapping.

Main Methods:

• Numerical simulations were employed to model acoustic forces and hydrodynamic shielding.
• Analysis of acoustic interactions with varying particle concentrations and the presence of seed particles.
• Investigation of trapping mechanisms for monodisperse versus seeded nanoparticle suspensions.

Main Results:

• The trapping mechanism relies on a synergistic interplay between hydrodynamic shielding and acoustic forces.
• Acoustic interactions are significant only when larger seed particles are present.
• Acoustic forces are negligible when trapping monodisperse nanoparticles without seed particles.

Conclusions:

• The combined effect of acoustic forces and hydrodynamic shielding is essential for effective nanoparticle trapping.
• Seed particles play a critical role in enabling significant acoustic interactions for nanoparticle manipulation.
• Numerical results suggest the potential for density-selective nanoparticle trapping using this approach.