Ultrasonic Extraction and Manipulation of Droplets from a Liquid-Liquid Interface with Near-Field Acoustic Tweezers

Abstract

The acoustic radiation force and associated trapping by ``acoustic tweezers'' is an efficient means of particle manipulation in a variety of applications, although this trapping is highly sensitive to parameters of the object and beam. The authors show how to extract and manipulate droplets from a fluid interface without mechanical contact, using near-field acoustic tweezers, with the near-field pressure gradient allowing automatic trapping after extraction. The strong, flexible trapping here is an advantage over traditional tweezers based on focused beams or standing waves, and can be of great importance in both laboratory and industrial settings.