Three-dimensional continuous particle focusing in a microfluidic channel via standing surface acoustic waves (SSAW)

We present a numerical and experimental study of acoustophoretic manipulation in a microfluidic channel using dual-wavelength standing surface acoustic waves (SSAWs) to transport microparticles into different outlets. The SSAW fields were excited by interdigital transducers (IDTs) composed of two different pitches connected in parallel and series on a lithium niobate substrate such that it yielded spatially superimposed and separated dual-wavelength SSAWs, respectively. SSAWs of a singltablee target wavelength can be efficiently excited by giving an RF voltage of frequency determined by the ratio of the velocity of the SAW to the target IDT pitch (i.e., f = cSAW/p). However, the two-pitch IDTs with similar pitches excite, less efficiently, non-target SSAWs with the wavelength associated with the non-target pitch in addition to target SSAWs by giving the target single-frequency RF voltage. As a result, dual-wavelength SSAWs can be formed. Simulated results revealed variations of acoustic pressure fields induced by the dual-wavelength SSAWs and corresponding influences on the particle motion. The acoustic radiation force in the acoustic pressure field was calculated to pinpoint zero-force positions and simulate particle motion trajectories. Then, dual-wavelength SSAW acoustofluidic devices were fabricated in accordance with the simulation results to experimentally demonstrate switching of SSAW fields as a means of transporting particles. The effects of non-target SSAWs on pre-actuating particles were predicted and observed. The study provides the design considerations needed for the fabrication of acoustofluidic devices with IDT-excited multi-wavelength SSAWs for acoustophoresis of microparticles.

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Continuous separation of particles in a PDMS microfluidic channel via travelling surface acoustic waves (TSAW)

Lab on a Chip ◽

10.1039/c3lc50451d ◽

2013 ◽

Vol 13 (21) ◽

pp. 4210 ◽

Cited By ~ 118

Author(s):

Ghulam Destgeer ◽

Kyung Heon Lee ◽

Jin Ho Jung ◽

Anas Alazzam ◽

Hyung Jin Sung

Keyword(s):

Acoustic Waves ◽

Surface Acoustic Waves ◽

Microfluidic Channel ◽

Continuous Separation

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Acoustic tweezers via sub–time-of-flight regime surface acoustic waves

Science Advances ◽

10.1126/sciadv.1600089 ◽

2016 ◽

Vol 2 (7) ◽

pp. e1600089 ◽

Cited By ~ 67

Author(s):

David J. Collins ◽

Citsabehsan Devendran ◽

Zhichao Ma ◽

Jia Wei Ng ◽

Adrian Neild ◽

...

Keyword(s):

Optical Tweezers ◽

Acoustic Waves ◽

Optical Waveguides ◽

Surface Acoustic Waves ◽

Time Of Flight ◽

Microfluidic Channel ◽

Two Dimensions ◽

Acoustic Standing Wave ◽

Spatial Dimensions ◽

Acoustic Tweezers

Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides.

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Measurement of the acoustic streaming pattern in a standing surface acoustic wave field

14th International Symposium on Particle Image Velocimetry ◽

10.18409/ispiv.v1i1.24 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Sebastian Sachs ◽

Christian Cierpka ◽

Jörg König

Keyword(s):

Wave Field ◽

Acoustic Waves ◽

Acoustic Radiation ◽

Electrical Power ◽

Surface Acoustic Waves ◽

Acoustic Streaming ◽

Fluid Motion ◽

Three Dimensional ◽

Radiation Force ◽

Flow Measurements

The application of standing surface acoustic waves (sSAW) has enabled the development of many flexible and easily scalable concepts for the fractionation of particle solutions in the field of microfluidic lab-ona-chip devices. In this context, the acoustic radiation force (ARF) is often employed for the targeted manipulation of particle trajectories, whereas acoustically induced flows complicate efficient fractionation in many systems [Sehgal and Kirby (2017)]. Therefore, a characterization of the superimposed fluid motion is essential for the design of such devices. The present work focuses on a structural analysis of the acousticallyexcited flow, both in the center and in the outer regions of the standing wave field. For this, experimental flow measurements were conducted using astigmatism particle tracking velocimetry (APTV) [Cierpka et al. (2010)]. Through multiple approaches, we address the specific challenges for reliable velocity measurements in sSAW due to limited optical access, the influence of the ARF on particle motion, and regions of particle depletion caused by multiple pressure nodes along the channel width and height. Variations in frequency, channel geometry, and electrical power allow for conclusions to be drawn on the formation of a complex, three-dimensional vortex structure at the beginning and end of the sSAW.

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Ultra-High Frequency Sound Waves for Microparticle Separation

Volume 2A: Fora, Part 2 ◽

10.1115/ajkfluids2015-18682 ◽

2015 ◽

Author(s):

Ghulam Destgeer ◽

Anas Alazzam ◽

Hyung Jin Sung

Keyword(s):

Acoustic Waves ◽

High Frequency ◽

Surface Acoustic Waves ◽

Microfluidic Channel ◽

Sound Waves ◽

Ultra High Frequency ◽

High Frequency Sound ◽

Frequency Sound ◽

Sheath Fluid ◽

Order Of Magnitude

In this study, we have demonstrated a particle separation device taking advantage of the ultra-high frequency sound waves. The sound waves, in the form of surface acoustic waves, are produced by an acoustofluidic platform build on top of a piezoelectric substrate bonded to a microfluidic channel. The particles’ mixture, pumped through the microchannel, is focused using a sheath fluid. A travelling surface acoustic wave (TSAW), propagating normal to the flow, interacts with the particles and deflect them from their original path to induce size-based separation in a continuous flow. We initially started the experiment with 40 MHz TSAWs for deflecting 10 μm diameter polystyrene particles but failed. However, larger diameter particles (∼ 30 μm) were successfully deflected from their streamlines and separated from the smaller particles (∼ 10 μm) using TSAWs with 40 MHz frequency. The separation of smaller diameter particles (3, 5 and 7 μm) was also achieved using an order of magnitude higher-frequency (∼ 133 MHz) TSAWs.

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Diffraction-based acoustic manipulation in microchannels enables continuous particle and bacteria focusing

Lab on a Chip ◽

10.1039/d0lc00397b ◽

2020 ◽

Vol 20 (15) ◽

pp. 2674-2688 ◽

Cited By ~ 1

Author(s):

Citsabehsan Devendran ◽

Kyungyong Choi ◽

Jongyoon Han ◽

Ye Ai ◽

Adrian Neild ◽

...

Keyword(s):

Acoustic Wave ◽

Surface Acoustic Wave ◽

Acoustic Waves ◽

Surface Acoustic Waves ◽

Continuous Particle ◽

Acoustic Phenomenon

We explore a unique diffractive acoustic phenomenon arising from a surface acoustic wave and channel elements, which we term diffractive acoustic surface acoustic waves (DASAW), which can be applied robustly for all channel orientations.

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