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Investigation of two-dimensional acoustic resonant modes in a particle separator

Investigation of two-dimensional acoustic resonant modes in a particle separator
Investigation of two-dimensional acoustic resonant modes in a particle separator
Within an acoustic standing wave particles experience acoustic radiation forces, a phenomenon which is exploited in particle or cell manipulation devices. When developing such devices, one-dimensional acoustic characteristics corresponding to the transducer(s) are typically of most importance and determine the primary radiation forces acting on the particles. However, radiation forces have also been observed to act in the lateral direction, perpendicular to the primary radiation force, forming striated patterns. These lateral forces are due to lateral variations in the acoustic field influenced by the geometry and materials used in the resonator. The ability to control them would present an advantage where their effect is either detrimental or beneficial to the particle manipulation process.

The two-dimensional characteristics of an ultrasonic separator device have been modelled within a finite element analysis (FEA) package. The fluid chamber of the device, within which the standing wave is produced, has a width to height ratio of approximately 30:1 and it is across the height that a half-wavelength standing wave is produced to control particle movement. Two-dimensional modal analyses have calculated resonant frequencies which agree well with both the one-dimensional modelling of the device and experimentally measured frequencies. However, these two-dimensional analyses also reveal that these modes exhibit distinctive periodic variations in the acoustic pressure field across the width of the fluid chamber. Such variations lead to lateral radiation forces forming particle bands (striations) and are indicative of enclosure modes.

The striation spacings predicted by the FEA simulations for several modes compare well with those measured experimentally for the ultrasonic particle separator device. It is also shown that device geometry and materials control enclosure modes and therefore the strength and characteristics of lateral radiation forces, suggesting the potential use of FEA in designing for the control of enclosure modes in similar particle manipulator devices.
lateral radiation force, fea, particles
0041-624X
e467-e471
Townsend, R.J.
0452b21c-a758-4d4a-925b-1511d9296d62
Hill, M.
0cda65c8-a70f-476f-b126-d2c4460a253e
Harris, N.R.
237cfdbd-86e4-4025-869c-c85136f14dfd
White, N.M.
c7be4c26-e419-4e5c-9420-09fc02e2ac9c
Townsend, R.J.
0452b21c-a758-4d4a-925b-1511d9296d62
Hill, M.
0cda65c8-a70f-476f-b126-d2c4460a253e
Harris, N.R.
237cfdbd-86e4-4025-869c-c85136f14dfd
White, N.M.
c7be4c26-e419-4e5c-9420-09fc02e2ac9c

Townsend, R.J., Hill, M., Harris, N.R. and White, N.M. (2006) Investigation of two-dimensional acoustic resonant modes in a particle separator [in special issue: Proceedings of Ultrasonics International (UI’05) and World Congress on Ultrasonics (WCU)] Ultrasonics, 44, supplement , e467-e471.

Record type: Article

Abstract

Within an acoustic standing wave particles experience acoustic radiation forces, a phenomenon which is exploited in particle or cell manipulation devices. When developing such devices, one-dimensional acoustic characteristics corresponding to the transducer(s) are typically of most importance and determine the primary radiation forces acting on the particles. However, radiation forces have also been observed to act in the lateral direction, perpendicular to the primary radiation force, forming striated patterns. These lateral forces are due to lateral variations in the acoustic field influenced by the geometry and materials used in the resonator. The ability to control them would present an advantage where their effect is either detrimental or beneficial to the particle manipulation process.

The two-dimensional characteristics of an ultrasonic separator device have been modelled within a finite element analysis (FEA) package. The fluid chamber of the device, within which the standing wave is produced, has a width to height ratio of approximately 30:1 and it is across the height that a half-wavelength standing wave is produced to control particle movement. Two-dimensional modal analyses have calculated resonant frequencies which agree well with both the one-dimensional modelling of the device and experimentally measured frequencies. However, these two-dimensional analyses also reveal that these modes exhibit distinctive periodic variations in the acoustic pressure field across the width of the fluid chamber. Such variations lead to lateral radiation forces forming particle bands (striations) and are indicative of enclosure modes.

The striation spacings predicted by the FEA simulations for several modes compare well with those measured experimentally for the ultrasonic particle separator device. It is also shown that device geometry and materials control enclosure modes and therefore the strength and characteristics of lateral radiation forces, suggesting the potential use of FEA in designing for the control of enclosure modes in similar particle manipulator devices.

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More information

e-pub ahead of print date: 2 June 2006
Published date: 22 December 2006
Keywords: lateral radiation force, fea, particles

Identifiers

Local EPrints ID: 43342
URI: http://eprints.soton.ac.uk/id/eprint/43342
ISSN: 0041-624X
PURE UUID: 7704070c-1091-4aa4-9844-3a04459ca855
ORCID for M. Hill: ORCID iD orcid.org/0000-0001-6448-9448
ORCID for N.R. Harris: ORCID iD orcid.org/0000-0003-4122-2219
ORCID for N.M. White: ORCID iD orcid.org/0000-0003-1532-6452

Catalogue record

Date deposited: 23 Jan 2007
Last modified: 30 Oct 2017 16:24

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Contributors

Author: R.J. Townsend
Author: M. Hill ORCID iD
Author: N.R. Harris ORCID iD
Author: N.M. White ORCID iD

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