Optical Calibration of Holographic Acoustic Tweezers

Abstract

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 acousto-optical setups.

3D Integral Imaging of Acoustically Trapped Objects

“…Similar to OT systems, the calibration of the trap stiffness can be useful for knowing the setup capability to hold and manipulate the trapped objects 10,31 . To perform such a task, we provide a trajectory-based investigation on the stiffness of the ATs.…”

“…Therefore, depending on the predesigned arrangements of the acoustic sources and properties of the object in the nodal area, the gradient force can trap the object toward the nodal point. By smart arrangements of the acoustic source arrays one can superpose the gradient forces to achieve a tight AT 24,25,30,31 .…”