[The Journal of the Acoustical Society of America] Acoustic force measurements on polymer-coated mic
This work presents an acoustofluidic device for manipulating coated microbubbles, designed for the simultaneous use of optical and acoustical tweezers. A comprehensive characterization of the acoustic pressure in the device is presented, obtained by the synergic use of different techniques in the range of acoustic frequencies where visual observations showed aggregation of polymer-coated microbubbles. In absence of bubbles, the combined use of laser vibrometry and finite element modelling supported a non-invasive measurement of the acoustic pressure and an enhanced understanding of the system resonances. Calibrated holographic optical tweezers were used for direct measurements of the acoustic forces acting on an isolated microbubble, at low driving pressures, and to confirm the spatial distribution of the acoustic field. This allowed quantitative acoustic pressure measurements by particle tracking, using polystyrene beads, and an evaluation of the related uncertainties. This process facilitated the extension of tracking to microbubbles, which have a negative acoustophoretic contrast factor, allowing acoustic force measurements on bubbles at higher pressures than optical tweezers, highlighting four peaks in the acoustic response of the device. Results and methodologies are relevant to acoustofluidic applications requiring a precise characterization of the acoustic field and, in general, to biomedical applications with microbubbles or deformable particles.
Gianluca Memolia), Christopher R. Furyb), Kate O. Baxter, and Pierre N. Gélatc) Department of Acoustics, National Physical Laboratory, Hampton Road, Teddington TW11 0LW, United Kingdom Philip H. Jones Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom Hide Affiliations a)Current address: INTERACT Lab, School of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9RH, United Kingdom. Electronic mail: firstname.lastname@example.org
b)Also at: Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
c)Current address: Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
The Journal of the Acoustical Society of America 141, 3364 (2017); doi: http://dx.doi.org/10.1121/1.4979933