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

Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA.
Lab on a Chip (Impact Factor: 6.12). 06/2011; 11(14):2319-24. DOI: 10.1039/c1lc20042a
Source: PubMed


Three-dimensional (3D) continuous microparticle focusing has been achieved in a single-layer polydimethylsiloxane (PDMS) microfluidic channel using a standing surface acoustic wave (SSAW). The SSAW was generated by the interference of two identical surface acoustic waves (SAWs) created by two parallel interdigital transducers (IDTs) on a piezoelectric substrate with a microchannel precisely bonded between them. To understand the working principle of the SSAW-based 3D focusing and investigate the position of the focal point, we computed longitudinal waves, generated by the SAWs and radiated into the fluid media from opposite sides of the microchannel, and the resultant pressure and velocity fields due to the interference and reflection of the longitudinal waves. Simulation results predict the existence of a focusing point which is in good agreement with our experimental observations. Compared with other 3D focusing techniques, this method is non-invasive, robust, energy-efficient, easy to implement, and applicable to nearly all types of microparticles.

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    • "Resolution -From the work of Shi et al [7], 10 μm particle focusing was achieved in 2009, and more recently this was achieved in three dimensional particle streaming [8]. While theoretically far higher resolution can be achieved with SSAW techniques at higher excitation frequencies, the practical limitation of the maximum particle size approaching the wavelength of the excitation signal, means a 10 μm particle spread after ordering remains realistic. "
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    ABSTRACT: As the pressure continues to grow on Diamond and the world's synchrotrons for higher throughput of diffraction experiments, new and novel techniques are required for presenting micron dimension crystals to the X ray beam. Currently this task is both labour intensive and primarily a serial process. Diffraction measurements typically take milliseconds but sample preparation and presentation can reduce throughput down to 4 measurements an hour. With beamline waiting times as long as two years it is of key importance for researchers to capitalize on available beam time, generating as much data as possible. Other approaches detailed in the literature [1] [2] [3] are very much skewed towards automating, with robotics, the actions of a human protocols. The work detailed here is the development and discussion of a bottom up approach relying on SSAW self assembly, including material selection, microfluidic integration and tuning of the acoustic cavity to order the protein crystals.
    Nanotech 2015; 06/2015
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    • "Microparticles concentrate along both the width and height of the channel as modeled by Shi et al. [Shi 2011], who simplified the PDMS walls of the channel as ideal reflectors in simulation. However, preliminary models reveal acoustic potential density in the PDMS channel boundaries. "
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    ABSTRACT: We describe lithium niobate SAW devices and PDMS microfluidic channels with which we study microparticle movement. We generate standing surface acoustic waves (with wavelengths of 200 micrometers) and show that microparticles (between 5 and 35 micrometers in diameter) move to nodes or antinodes. We report measurements of device response in the presence and absence of the microfluidic channel, which we combine with finite element simulation modeling to extract estimates of the PDMS damping.
    SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring; 04/2013
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    • "However, since the operating frequencies of SAW separation devices (tens of MHz) correspond to time scales smaller than the molecular relaxation time and certainly any relaxation time of the cellular structures, there is no shear damage with these high frequency devices [31,32]. SAW devices have been investigated in wide variety of applications including fluid-mixing [33,34], fluid-pumping [35,36], particle focusing [30,37], and particle sorting/collection [38,39] in microchannels. Recently, standing surface acoustic waves (SSAW), generated by interdigitated microelectrodes on a piezoelectric substrate, have been demonstrated to separate polystyrene microparticles [40]. "
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    ABSTRACT: Particle separation is of great interest in many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In this paper, we present a microfluidic platform for sheathless particle separation using standing surface acoustic waves. In this platform, particles are first lined up at the center of the channel without introducing any external sheath flow. The particles are then entered into the second stage where particles are driven towards the off-center pressure nodes for size based separation. The larger particles are exposed to more lateral displacement in the channel due to the acoustic force differences. Consequently, different-size particles are separated into multiple collection outlets. The prominent feature of the present microfluidic platform is that the device does not require the use of the sheath flow for positioning and aligning of particles. Instead, the sheathless flow focusing and separation are integrated within a single microfluidic device and accomplished simultaneously. In this paper, we demonstrated two different particle size-resolution separations; (1) 3 μm and 10 μm and (2) 3 μm and 5 μm. Also, the effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. These technologies have potential to impact broadly various areas including the essential microfluidic components for lab-on-a-chip system and integrated biological and biomedical applications.
    Sensors 12/2012; 12(1):905-22. DOI:10.3390/s120100905 · 2.25 Impact Factor
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