Next Article in Journal
Alkali Vapor MEMS Cells Technology toward High-Vacuum Self-Pumping MEMS Cell for Atomic Spectroscopy
Next Article in Special Issue
Ultrasonic Based Tissue Modelling and Engineering
Previous Article in Journal
From Lab on a Chip to Point of Care Devices: The Role of Open Source Microcontrollers
Previous Article in Special Issue
Acoustic Manipulation of Bio-Particles at High Frequencies: An Analytical and Simulation Approach
Open AccessArticle

Acoustofluidic Measurements on Polymer-Coated Microbubbles: Primary and Secondary Bjerknes Forces

School of Engineering and Informatics, University of Sussex, BN1 9QJ Falmer, UK
National Physical Laboratory, TW11 0LW Teddington, UK
Author to whom correspondence should be addressed.
Micromachines 2018, 9(8), 404;
Received: 13 June 2018 / Revised: 5 August 2018 / Accepted: 9 August 2018 / Published: 15 August 2018
(This article belongs to the Special Issue Acoustofluidics in Medicine and Biology)
The acoustically-driven dynamics of isolated particle-like objects in microfluidic environments is a well-characterised phenomenon, which has been the subject of many studies. Conversely, very few acoustofluidic researchers looked at coated microbubbles, despite their widespread use in diagnostic imaging and the need for a precise characterisation of their acoustically-driven behaviour, underpinning therapeutic applications. The main reason is that microbubbles behave differently, due to their larger compressibility, exhibiting much stronger interactions with the unperturbed acoustic field (primary Bjerknes forces) or with other bubbles (secondary Bjerknes forces). In this paper, we study the translational dynamics of commercially-available polymer-coated microbubbles in a standing-wave acoustofluidic device. At increasing acoustic driving pressures, we measure acoustic forces on isolated bubbles, quantify bubble-bubble interaction forces during doublet formation and study the occurrence of sub-wavelength structures during aggregation. We present a dynamic characterisation of microbubble compressibility with acoustic pressure, highlighting a threshold pressure below which bubbles can be treated as uncoated. Thanks to benchmarking measurements under a scanning electron microscope, we interpret this threshold as the onset of buckling, providing a quantitative measurement of this parameter at the single-bubble level. For acoustofluidic applications, our results highlight the limitations of treating microbubbles as a special case of solid particles. Our findings will impact applications where knowing the buckling pressure of coated microbubbles has a key role, like diagnostics and drug delivery. View Full-Text
Keywords: microbubbles; acoustofluidics; Bjerknes forces; compressibility microbubbles; acoustofluidics; Bjerknes forces; compressibility
Show Figures

Figure 1

MDPI and ACS Style

Memoli, G.; Baxter, K.O.; Jones, H.G.; Mingard, K.P.; Zeqiri, B. Acoustofluidic Measurements on Polymer-Coated Microbubbles: Primary and Secondary Bjerknes Forces. Micromachines 2018, 9, 404.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Back to TopTop