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Measuring the local pressure amplitude in microchannel acoustophoresis

Barnkob, Rune; Augustsson, Per LU ; Laurell, Thomas LU and Bruus, Henrik (2010) In Lab on A Chip 10(5). p.563-570
Abstract
A new method is reported on how to measure the local pressure amplitude and the Q factor of ultrasound resonances in microfluidic chips designed for acoustophoresis of particle suspensions. The method relies on tracking individual polystyrene tracer microbeads in straight water-filled silicon/glass microchannels. The system is actuated by a PZT piezo transducer attached beneath the chip and driven by an applied ac voltage near its eigenfrequency of 2 MHz. For a given frequency a number of particle tracks are recorded by a CCD camera and fitted to a theoretical expression for the acoustophoretic motion of the microbeads. From the curve fits we obtain the acoustic energy density, and hence the pressure amplitude as well as the... (More)
A new method is reported on how to measure the local pressure amplitude and the Q factor of ultrasound resonances in microfluidic chips designed for acoustophoresis of particle suspensions. The method relies on tracking individual polystyrene tracer microbeads in straight water-filled silicon/glass microchannels. The system is actuated by a PZT piezo transducer attached beneath the chip and driven by an applied ac voltage near its eigenfrequency of 2 MHz. For a given frequency a number of particle tracks are recorded by a CCD camera and fitted to a theoretical expression for the acoustophoretic motion of the microbeads. From the curve fits we obtain the acoustic energy density, and hence the pressure amplitude as well as the acoustophoretic force. By plotting the obtained energy densities as a function of applied frequency, we obtain Lorentzian line shapes, from which the resonance frequency and the Q factor for each resonance peak are derived. Typical measurements yield acoustic energy densities of the order of 10 J/m(3), pressure amplitudes of 0.2 MPa, and Q factors around 500. The observed half wavelength of the transverse acoustic pressure wave is equal within 2% to the measured width w = 377 mu m of the channel. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Lab on A Chip
volume
10
issue
5
pages
563 - 570
publisher
Royal Society of Chemistry
external identifiers
  • wos:000274581100006
  • scopus:76949091885
ISSN
1473-0189
DOI
10.1039/b920376a
language
English
LU publication?
yes
id
68a308f5-f66a-484f-8c9c-0c21b1499be5 (old id 1568080)
date added to LUP
2010-03-24 11:15:35
date last changed
2018-09-09 03:13:00
@article{68a308f5-f66a-484f-8c9c-0c21b1499be5,
  abstract     = {A new method is reported on how to measure the local pressure amplitude and the Q factor of ultrasound resonances in microfluidic chips designed for acoustophoresis of particle suspensions. The method relies on tracking individual polystyrene tracer microbeads in straight water-filled silicon/glass microchannels. The system is actuated by a PZT piezo transducer attached beneath the chip and driven by an applied ac voltage near its eigenfrequency of 2 MHz. For a given frequency a number of particle tracks are recorded by a CCD camera and fitted to a theoretical expression for the acoustophoretic motion of the microbeads. From the curve fits we obtain the acoustic energy density, and hence the pressure amplitude as well as the acoustophoretic force. By plotting the obtained energy densities as a function of applied frequency, we obtain Lorentzian line shapes, from which the resonance frequency and the Q factor for each resonance peak are derived. Typical measurements yield acoustic energy densities of the order of 10 J/m(3), pressure amplitudes of 0.2 MPa, and Q factors around 500. The observed half wavelength of the transverse acoustic pressure wave is equal within 2% to the measured width w = 377 mu m of the channel.},
  author       = {Barnkob, Rune and Augustsson, Per and Laurell, Thomas and Bruus, Henrik},
  issn         = {1473-0189},
  language     = {eng},
  number       = {5},
  pages        = {563--570},
  publisher    = {Royal Society of Chemistry},
  series       = {Lab on A Chip},
  title        = {Measuring the local pressure amplitude in microchannel acoustophoresis},
  url          = {http://dx.doi.org/10.1039/b920376a},
  volume       = {10},
  year         = {2010},
}