title: Poloidal flow and toroidal particle ring formation in a sessile drop driven by megahertz order vibration.
abstract: Poloidal flow is curiously formed in a microliter sessile water drop over 157-225 MHz because of acoustic streaming from three-dimensional standing Lamb waves in a lithium niobate substrate. The flow possesses radial symmetry with downwelling at the center and upwelling around the periphery of the drop. Outside this frequency range, the attenuation occurs over a length scale incompatible with the drop size and the poloidal flow vanishes. Remarkably, shear-induced migration was found to drive toroidal particle ring formation with diameters inversely proportional to the frequency of the acoustic irradiation.
authors.affiliation: Micro/Nanophysics Research Laboratory, Royal Melbourne Institute of Technology (RMIT) University , Melbourne, Victoria 3000, Australia.
authors.forename: Amgad R
authors.initials: AR
authors.lastname: Rezk
authors.forename: Leslie Y
authors.initials: LY
authors.lastname: Yeo
authors.forename: James R
authors.initials: JR
authors.lastname: Friend