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

We report the extraction, capture, and manipulation of a droplet from a liquid-liquid surface using the acoustic near field from a fraxicon lens transducer. The lens is submerged in water, which shares a planar boundary with a reservoir of carbon tetrachloride (CCl4). The ultrasonic beam exerts a negative radiation pressure, drawing the CCl4 up into the water, and a droplet of wavelength order is extracted out of the bulk liquid and sonically trapped. Our work demonstrates the means of producing and manipulating droplets from a fluid interface without mechanical contact using a near-field acoustic tweezer.