Modelling of layered resonators for ultrasonic separation

Hill, Martyn; Shen, Yijun; Hawkes, Jeremy J.

doi:10.1016/s0041-624x(02)00127-0

Cited by 109 publications

(73 citation statements)

References 6 publications

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“…Along this line Benes, Hill, Hawkes and co-workers were early in outlining models for the treatment of the two dimensional layered acoustic resonator. [27][28][29][30][31] Lately, it has proven useful to model resonant microchannel or microcavity lab-on-a-chip systems by the Helmholtz pressure-wave eigenvalue equation for the actual chip geometries. In the 2D-limit, i.e.…”

Section: Introductionmentioning

confidence: 99%

Measuring the local pressure amplitude in microchannel acoustophoresis

et al. 2010

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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 ¼ 377 mm of the channel.

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Section: Introductionmentioning

confidence: 99%

Measuring the local pressure amplitude in microchannel acoustophoresis

et al. 2010

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“…However, the use of a simple planar layered resonator with a single transducer [1,17,18] offers the simplest approach to establishing a predictable USW suitable for particle movement.…”

Section: Introductionmentioning

confidence: 99%

“…Modelling of planar multilayered resonant structures allows appropriate layer thicknesses to be calculated for placement of pressure nodes at known positions within the fluid layer [18,21], including placing the pressure minimum at the reflector boundary [22]. As an example, Figure 1 shows a multilayer structure, typically used as the basis for an ultrasonic manipulator.…”

Section: Introductionmentioning

confidence: 99%

Mode-switching: A new technique for electronically varying the agglomeration position in an acoustic particle manipulator

et al. 2010

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Acoustic radiation forces offer a means of manipulating particles within a fluid. Much interest in recent years has focussed on the use of radiation forces in microfluidic (or "lab on a chip") devices. Such devices are well matched to the use of ultrasonic standing waves in which the resonant dimensions of the chamber are smaller than the ultrasonic wavelength in use. However, such devices have typically been limited to moving particles to one or two predetermined planes, whose positions are determined by acoustic pressure nodes/antinodes set up in the ultrasonic standing wave. In most cases devices have been designed to move particles to either the centre or (more recently) the side of a flow channel using ultrasonic frequencies that produce a half or quarter wavelength over the channel respectively.It is demonstrated here that by rapidly switching back and forth between half and quarter wavelength frequencies -mode-switching -a new agglomeration position is established that permits beads to be brought to any arbitrary point between the half and quarter wave nodes. This new agglomeration position is effectively a position of stable equilibrium. This has many potential applications, particularly in cell sorting and manipulation. It should also enable precise control of agglomeration position to be maintained regardless of manufacturing tolerances, temperature variations, fluid medium characteristics and particle concentration.

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“…Thus a thorough understanding of the 2-D nature of the acoustic field in such a system is needed to ensure that beads can be suitably controlled. In this paper we investigate the axial acoustic field distribution using a 1-D acoustic impedance transfer model [2], and also finite element analysis to model the lateral variation of the field.…”

Section: Introductionmentioning

confidence: 99%

Multi-modal particle manipulator to enhance bead-based bioassays

et al. 2010

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By sequentially pushing micro-beads towards and away from a sensing surface, we show that ultrasonic radiation forces can be used to enhance the interaction between a functionalized glass surface and polystyrene microbeads, and identify those that bind to the surface by illuminating bound beads using an evanescent field generated by guided light. School of Electronics and Computer Science, University of Southampton, SO17 1BJ, UKThe movement towards and immobilization of streptavidin coated beads onto a biotin functionalized waveguide surface is achieved by using a quarter-wavelength mode pushing beads onto the surface, while the removal of non-specifically bound beads uses a second quarter-wavelength mode which exhibits a kinetic energy maximum at the boundary between the carrier layer and fluid, drawing beads towards this surface. This has been achieved using a multi-modal acoustic device which exhibits both of these quarter-wavelength resonances. Both 1-D acoustic modelling and finite element analysis has been used to design this device and to investigate the spatial uniformity of the field.We demonstrate experimentally that 90% of specifically bound beads remain attached after applying ultrasound, with 80% of non-specifically bound control beads being successfully removed acoustically. This approach overcomes problems associated with lengthy sedimentation processes used for bead-based bioassays and surface (electrostatic) forces, which delay or prevent immobilisation. We explain the potential of this technique in the development of DNA and protein assays in terms of detection speed and multiplexing.PACS code: 43.90 v

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Modelling of layered resonators for ultrasonic separation

Cited by 109 publications

References 6 publications

Measuring the local pressure amplitude in microchannel acoustophoresis

Measuring the local pressure amplitude in microchannel acoustophoresis

Mode-switching: A new technique for electronically varying the agglomeration position in an acoustic particle manipulator

Multi-modal particle manipulator to enhance bead-based bioassays

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