Trapping of microparticles in the near field of an ultrasonic transducer

Lilliehorn, Tobias; Simu, Urban; Nilsson, Mikael; Almqvist, Monica; Stepinski, Tadeusz; Laurell, Thomas; Nilsson, Johan; Johansson, Stefan

doi:10.1016/j.ultras.2004.11.001

Cited by 135 publications

(110 citation statements)

References 18 publications

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“…Several different approaches have been employed for the manipulation of particles using ultrasonic fields. For example, focussed ultrasound [2,3] or near-field effects [4] can be used to trap particles prior to analysis, particles can be moved by using two or more opposing transducers to modulate the standing wave field [5,6], or particles can be held and moved within USWs excited by plate waves coupled into the containing fluid [7,8]. However, the use of a simple planar layered resonator with a single transducer [9][10][11] offers the simplest approach to establishing a USW suitable for particle movement.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

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

2008

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“…The modelling of lateral fields has been described by Neild et al [4], Manneberg et al [5], Lilliehorn et al [6],…”

Section: Construction Of Modelmentioning

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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“…A summary of the various layers and their properties can be seen in Table 2. During operation, the micro-engineered device and related systems reported in the literature are observed to form striations, which in the case of the micro-engineered device are likely to be a result of acoustic enclosure modes giving rise to lateral acoustic radiation forces [16], although other possible causes include nearfield effects from the transducer, which have been used to trap particles [17], and structural modes in the surrounding material that can be excited deliberately [10]. To suppress enclosure modes and promote a more uniform nodal plane, the compliant silicone gasket material used to seal the main fluid chamber also forms the side-walls of the chamber [16].…”

Section: Constructionmentioning

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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Trapping of microparticles in the near field of an ultrasonic transducer

Cited by 135 publications

References 18 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

Multi-modal particle manipulator to enhance bead-based bioassays

Performance of a quarter-wavelength particle concentrator

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