Optical Calibration of Holographic Acoustic Tweezers

Recently, acoustic tweezers based on an array of ultrasonic transducers have been reported taking inspiration from holographic optical tweezers. In the latter technique, the calibration of the optical trap is an essential procedure to obtain the trap stiffnesses. On the contrary, in the case of acoustic tweezers the calibration of the acoustic forces is seldom carried out. To cover this gap, in this work, we adapt the calibration protocols employed in optical tweezers to acoustic tweezers based on arrays of ultrasonic transducers. We measure trap stiffnesses in the mN/m range that are consistent with theoretical estimates obtained by calculations of the acoustic radiation forces based on the Gor'kov potential. This work gives a common framework to the optical and acoustic manipulation communities, paving the way to a consistent calibration of hybrid acoustooptical setups.

Automated summary

Recently, acoustic tweezers inspired by holographic optical tweezers have been developed. The calibration of optical trap stiffnesses is essential in the latter technique, but seldom carried out in acoustic tweezers. In this work, the calibration protocols used in optical tweezers are adapted for acoustic tweezers based on ultrasonic transducer arrays. The measured trap stiffnesses are consistent with theoretical estimates, providing a common framework for optical and acoustic manipulation communities and enabling consistent calibration of hybrid acoustooptical setups.