Kilohertz-Frequency Rotation of Acoustically Levitated Particles

Area of Science:

• Acoustic manipulation
• Particle dynamics
• Transducer technology

Background:

• Rotational frequency of acoustically levitated particles is limited by suspension stability and driving torque.
• Previous methods have not achieved significant increases in rotational speed.

Purpose of the Study:

• To increase the rotational speed of acoustically levitated particles by over a factor of 10.
• To investigate the high-frequency resonance limits of piezoelectric transducers in acoustic fields.
• To explore a novel spherical ring arrangement of transducers and improved excitation concept.

Main Methods:

• Utilized a spherical ring arrangement of piezoelectric transducers.
• Implemented an improved excitation concept for enhanced driving torque.
• Conducted high-precision measurements of transducer characteristics beyond conventional frequency ranges.
• Employed calculations based on an analytical model to investigate field disturbances.

Main Results:

• Achieved a maximum rotational frequency of 3.6 kHz for asymmetric expanded polystyrene (EPS) particles.
• Demonstrated a rotational speed increase of more than a factor of 10 compared to prior studies.
• Identified high-frequency transducer resonances as a previously unexplored limit to particle manipulation rates at high speeds.

Conclusions:

• The novel transducer arrangement and excitation concept significantly enhance particle rotation speeds.
• High-frequency resonances of transducers introduce new limitations in acoustic manipulation, necessitating further investigation.
• This work pushes the boundaries of acoustic levitation and particle manipulation capabilities.