Enhanced particle focusing in microfluidic channels with standing surface acoustic waves

In Lab-On-a-chip devices, the separation and manipulation of micro-particles within microfluidic channels are important operations in the process of biological analyses. In this study, the microfluidic flow is coupled with acoustic waves through a 3D multi-physics numerical solution in order to generate optimized acoustic pressure pattern. Exploiting interdigital transducers (IDTs), surface acoustic waves (SAWs) are generated on the surface of a piezoelectric substrate (lithium niobate). These waves interfere constructively to generate a standing pressure field within a fluid contained in a microchannel placed between them. Several studies and applications have been reported exploiting two facing IDTs, effective in particle focusing due to the acoustic radiation force developed by the acoustic pressure. In this work, a configuration made by four IDTs is investigated to enhance the focusing effect and provide trapping capabilities. A complex matrix of pressure wave nodes (zero wave amplitude) and antinodes (maximum wave amplitude) is generated and optimized to acquire the right acoustic pressure pattern. Results obtained show particle focusing effects but also trapping on specific sites depending on the distribution of waves. These innovative results, based on multiphysics 3D numerical analysis, highlight the versatility and the efficiency of this configuration depending on the design of the microfluidic structure implemented in the SAW-based platform. Applications towards biological cell sorting and assembling can be considered based on this principle.

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Visualization of Surface Acoustic Waves in Thin Liquid Films

Scientific Reports ◽

10.1038/srep21980 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 20

Author(s):

R. W. Rambach ◽

J. Taiber ◽

C. M. L. Scheck ◽

C. Meyer ◽

J. Reboud ◽

...

Keyword(s):

Liquid Film ◽

Acoustic Waves ◽

Low Cost ◽

Thin Liquid Film ◽

Surface Acoustic Waves ◽

Liquid Films ◽

Theoretical Description ◽

Propagation Path ◽

Microfluidic Channels ◽

Potential Applications

Abstract We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfluidic channels. It also enables low-cost characterisation of IDT designs thereby allowing the determination of anisotropy and orientation of the piezoelectric substrate without the requirement for sophisticated and expensive equipment. Here, we show that the optical visibility of the sound path critically depends on the physical properties of the liquid film and identify heptane and methanol as most contrast rich solvents for visualization of SAW. We also provide a detailed theoretical description of this effect.

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Rapid additive-free bacteria lysis using traveling surface acoustic waves in microfluidic channels

Lab on a Chip ◽

10.1039/c9lc00656g ◽

2019 ◽

Vol 19 (24) ◽

pp. 4064-4070 ◽

Cited By ~ 4

Author(s):

Haiwei Lu ◽

Kirk Mutafopulos ◽

John A. Heyman ◽

Pascal Spink ◽

Liang Shen ◽

...

Keyword(s):

Microfluidic Device ◽

Acoustic Waves ◽

High Efficiency ◽

Surface Acoustic Waves ◽

Microfluidic Channels ◽

Wide Range

We introduce a microfluidic device that uses traveling surface acoustic waves to lyse bacteria with high efficiency. This lysis method should be applicable to a wide range of bacteria species and can be modified to analyze individual bacteria cells.

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

Lab on a Chip ◽

10.1039/c1lc20042a ◽

2011 ◽

Vol 11 (14) ◽

pp. 2319 ◽

Cited By ~ 132

Author(s):

Jinjie Shi ◽

Shahrzad Yazdi ◽

Sz-Chin Steven Lin ◽

Xiaoyun Ding ◽

I-Kao Chiang ◽

...

Keyword(s):

Acoustic Waves ◽

Surface Acoustic Waves ◽

Three Dimensional ◽

Microfluidic Channel ◽

Particle Focusing ◽

Continuous Particle

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Fabrication of Silicon Microfluidic Chips for Acoustic Particle Focusing Using Direct Laser Writing

Micromachines ◽

10.3390/mi11020113 ◽

2020 ◽

Vol 11 (2) ◽

pp. 113 ◽

Cited By ~ 2

Author(s):

Anna Fornell ◽

Per Söderbäck ◽

Zhenhua Liu ◽

Milena De Albuquerque Moreira ◽

Maria Tenje

Keyword(s):

Acoustic Waves ◽

Microfluidic Channel ◽

Microfluidic Channels ◽

Glass Wafer ◽

Microfluidic Chips ◽

Direct Laser Writing ◽

Laser Writing ◽

Simple Method ◽

Particle Focusing ◽

Direct Laser

We have developed a fast and simple method for fabricating microfluidic channels in silicon using direct laser writing. The laser microfabrication process was optimised to generate microfluidic channels with vertical walls suitable for acoustic particle focusing by bulk acoustic waves. The width of the acoustic resonance channel was designed to be 380 µm, branching into a trifurcation with 127 µm wide side outlet channels. The optimised settings used to make the microfluidic channels were 50% laser radiation power, 10 kHz pulse frequency and 35 passes. With these settings, six chips could be ablated in 5 h. The microfluidic channels were sealed with a glass wafer using adhesive bonding, diced into individual chips, and a piezoelectric transducer was glued to each chip. With acoustic actuation at 2.03 MHz a half wavelength resonance mode was generated in the microfluidic channel, and polystyrene microparticles (10 µm diameter) were focused along the centre-line of the channel. The presented fabrication process is especially interesting for research purposes as it opens up for rapid prototyping of silicon-glass microfluidic chips for acoustofluidic applications.

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Continuously phase-modulated standing surface acoustic waves for separation of particles and cells in microfluidic channels containing multiple pressure nodes

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/aa62d5 ◽

2017 ◽

Vol 50 (16) ◽

pp. 165401 ◽

Cited By ~ 4

Author(s):

Junseok Lee ◽

Chanryeol Rhyou ◽

Byungjun Kang ◽

Hyungsuk Lee

Keyword(s):

Acoustic Waves ◽

Surface Acoustic Waves ◽

Microfluidic Channels

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Numerical study of acoustophoretic manipulation of particles in microfluidic channels

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/09544119211024775 ◽

2021 ◽

pp. 095441192110247

Author(s):

Jun Ma ◽

Dongfang Liang ◽

Xin Yang ◽

Hanlin Wang ◽

Fangda Wu ◽

...

Keyword(s):

Acoustic Waves ◽

Acoustic Radiation ◽

Numerical Study ◽

Surface Acoustic Waves ◽

Radiation Force ◽

Suspended Particles ◽

Bottom Surface ◽

Microfluidic Channels ◽

The Finite Element Method ◽

First Order

The microfluidic technology based on surface acoustic waves (SAW) has been developing rapidly, as it can precisely manipulate fluid flow and particle motion at microscales. We hereby present a numerical study of the transient motion of suspended particles in a microchannel. In conventional studies, only the microchannel’s bottom surface generates SAW and only the final positions of the particles are analyzed. In our study, the microchannel is sandwiched by two identical SAW transducers at both the bottom and top surfaces while the channel’s sidewalls are made of poly-dimethylsiloxane (PDMS). Based on the perturbation theory, the suspended particles are subject to two types of forces, namely the Acoustic Radiation Force (ARF) and the Stokes Drag Force (SDF), which correspond to the first-order acoustic field and the second-order streaming field, respectively. We use the Finite Element Method (FEM) to compute the fluid responses and particle trajectories. Our numerical model is shown to be accurate by verifying against previous experimental and numerical results. We have determined the threshold particle size that divides the SDF-dominated regime and the ARF-dominated regime. By examining the time scale of the particle movement, we provide guidelines on the device design and operation.

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Characterization of RF Sputtered ZnO Piezoelectric Films Using Transmission Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100114050 ◽

1975 ◽

Vol 33 ◽

pp. 86-87

Author(s):

Kemining W. Yeh ◽

Richard S. Muller ◽

Wei-Kuo Wu ◽

Jack Washburn

Keyword(s):

Integrated Circuit ◽

Acoustic Waves ◽

New Technology ◽

Surface Acoustic Waves ◽

Electromechanical Properties ◽

Leading Role ◽

Saw Devices ◽

Transmission Electron ◽

High Degree

Considerable and continuing interest has been shown in the thin film transducer fabrication for surface acoustic waves (SAW) in the past few years. Due to the high degree of miniaturization, compatibility with silicon integrated circuit technology, simplicity and ease of design, this new technology has played an important role in the design of new devices for communications and signal processing. Among the commonly used piezoelectric thin films, ZnO generally yields superior electromechanical properties and is expected to play a leading role in the development of SAW devices.

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