Modelling of particle paths passing through an ultrasonic standing wave

Townsend, R.J.; Hill, Martyn; Harris, N.R.; White, NM

doi:10.1016/j.ultras.2004.01.025

Cited by 86 publications

(46 citation statements)

References 12 publications

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“…Hence there is an optimum positioning of the node that is dependent on the reflector thickness and a significant decrease in capture efficiency on each side of this thickness. When flow and particle tracking were added to the acoustic model [23] it was possible to predict the nature of the dependence of particle capture on reflector depth, as shown in Fig. 6b.…”

Section: Modelling Of Quarter-wavelength Devicesmentioning

confidence: 99%

Modelling for the robust design of layered resonators for ultrasonic particle manipulation

2008

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a b s t r a c t Several approaches have been described for the manipulation of particles within an ultrasonic field. Of those based on standing waves, devices in which the critical dimension of the resonant chamber is less than a wavelength are particularly well suited to microfluidic, or ''lab on a chip" applications. These might include pre-processing or fractionation of samples prior to analysis, formation of monolayers for cell interaction studies, or the enhancement of biosensor detection capability. The small size of microfluidic resonators typically places tight tolerances on the positioning of the acoustic node, and such systems are required to have high transduction efficiencies, for reasons of power availability and temperature stability. Further, the expense of many microfabrication methods precludes an iterative experimental approach to their development. Hence, the ability to design sub-wavelength resonators that are efficient, robust and have the appropriate acoustic energy distribution is extremely important. This paper discusses one-dimensional modelling used in the design of ultrasonic resonators for particle manipulation and gives example of their uses to predict and explain resonator behaviour. Particular difficulties in designing quarter wave systems are highlighted, and modelling is used to explain observed trends and predict performance of such resonators, including their performance with different coupling layer materials.

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Section: Modelling Of Quarter-wavelength Devicesmentioning

confidence: 99%

Modelling for the robust design of layered resonators for ultrasonic particle manipulation

2008

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“…44 In order to obtain a significant increase in particle concentration, the fluid flow must be split into the particle-rich and the particle-depleted fractions. 44,45 Based on this functioning principle, concentration of a range of particles including bacterial spores, biological cells and polystyrene spherical micro-beads has been demonstrated. 15,38,[46][47][48][49][50][51] Nordin and Laurell have recently demonstrated a very significant increase in concentration of red blood cells and prostate cancer cells (up to a maximum of ~200-fold), using a two-stages half-wavelength resonator.…”

Section: Introductionmentioning

confidence: 99%

“…15 However, direct manipulation of bodies as small as bacteria by means of ARFs represents a considerable physical challenge. 43 This is mainly due (i) to the fact that the acoustic primary radiation force scales with particle's volume, 45 and (ii) to the increased particle susceptibility with respect to hydrodynamic drag forces resulting from acoustic streaming or thermal convection. 52,53 It has been found that at diameters of around 1 μm there is a transition to drag-dominated behaviour for operating frequencies of ~2 MHz.…”

Section: Introductionmentioning

confidence: 99%

A thin-reflector microfluidic resonator for continuous-flow concentration of microorganisms: a new approach to water quality analysis using acoustofluidics

et al. 2014

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An acoustofluidic device has been developed for concentrating vegetative bacteria in a continuous-flow format. We show that it is possible to overcome the disruptive effects of acoustic streaming which typically dominate for small target particles, and demonstrate flow rates compatible with the testing of drinking water. The device consists of a thin-reflector multi-layered resonator, in which bacteria in suspension are levitated towards a glass surface under the action of acoustic radiation forces. In order to achieve robust device performance over long-term operation, functional tests have been carried out to (i) maintain device integrity over time and stabilise its resonance frequency, (ii) optimise the operational acoustic parameters, and (iii) minimise bacterial adhesion on the inner surfaces. Using the developed device, a significant increase in bacterial concentration has been achieved, up to a maximum of ~60-fold. The concentration performance of thin-reflector resonators was found to be superior to comparable half-wave resonators.

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“…An acoustic impedance transfer model can be used to predict the occurrence of various modes and their strength [6] in a multi-layered device, as is being considered here. When coupled with particle simulations [7], it is a useful tool to assess the likely particle separation.…”

Section: Introductionmentioning

confidence: 99%

Performance of a quarter-wavelength particle concentrator

et al. 2008

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a b s t r a c tA series of devices have been investigated which use acoustic radiation forces to concentrate micron sized particles. These multi-layered resonators use a quarter-wavelength resonance in order to position an acoustic pressure node close to the top surface of a fluid layer such that particles migrate towards this surface. As flow-through devices, it is then possible to collect a concentrate of particulates by drawing off the particle stream and separating it from the clarified fluid and so can operate continuously as opposed to batch processes such as centrifugation. The methods of construction are described which include a micro-fabricated, wet-etched device and a modular device fabricated using a micro-mill. These use silicon and macor, a machinable glass ceramic, as a carrier layer between the transducer and fluid channel, respectively. Simulations using an acoustic impedance transfer model are used to determine the influence of various design parameters on the acoustic energy density within the fluid layer and the nodal position. Concentration tests have shown up to 4.4-, 6.0-and 3.2-fold increases in concentration for 9, 3 and 1 lm diameter polystyrene particles, respectively. The effect of voltage and fluid flow rates on concentration performance is investigated and helps demonstrate the various factors which determine the increase in concentration possible.

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Modelling of particle paths passing through an ultrasonic standing wave

Cited by 86 publications

References 12 publications

Modelling for the robust design of layered resonators for ultrasonic particle manipulation

Modelling for the robust design of layered resonators for ultrasonic particle manipulation

A thin-reflector microfluidic resonator for continuous-flow concentration of microorganisms: a new approach to water quality analysis using acoustofluidics

Performance of a quarter-wavelength particle concentrator

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