The Experts below are selected from a list of 102882 Experts worldwide ranked by ideXlab platform
A.j. Walton - One of the best experts on this subject based on the ideXlab platform.
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high frequency microfluidic performance of linbo3 and zno surface Acoustic Wave devices
2014Co-Authors: Yuanjun Guo, Jikui Luo, Jian Zhou, A.j. WaltonAbstract:Rayleigh surface Acoustic Wave (SAW) devices based on 128° YX LiNbO3 and ZnO/Si substrates with different resonant frequencies from ∼62 MHz to ∼275 MHz were fabricated and characterized. Effects of SAW frequency and power on microfluidic performance (including streaming, pumping, and jetting) were investigated. SAW excitation frequency influenced the SAW attenuation length and hence the Acoustic energy absorbed by the liquid. At higher frequencies (e.g., above 100 MHz), the SAW dissipated into liquid decays more rapidly with much shorter decay lengths. Increasing the radio frequency (RF) frequencies of the devices resulted in an increased power threshold for streaming, pumping, and especially jetting, which is attributed to an increased absorption rate of Acoustic Wave energy. ZnO SAW devices could achieve similar streaming, pumping, and jetting effects as well as frequency effect, although the SAW signals are relatively weaker.
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surface Acoustic Wave nebulization on nanocrystalline zno film
2012Co-Authors: Yong Qing Fu, Yifan Li, Frank Placido, Chao Zhao, A.j. WaltonAbstract:Surface Acoustic Wave(SAW) nebulization/atomization has been realised on thin ZnOfilm based SAWdevices. The surface Acoustic Wave nebulization (SAWN) process has been observed to produce significant mist generation and ejected satellitedroplets. By modifying the geometry of the interdigitated transducers to reduce the Wavelengths from 400 μm to 120 μm, higher frequency SAWN has been achieved by increasing radio frequency driving frequencies from 11.8 MHz to 37.2 MHz, respectively. Compared with the commonly used LiNbO3 SAWN devices,ZnOfilmdevices exhibit better thermal dissipation, and to date, they have shown no susceptibility to substrate failure during fabrication or operation. They also have the added advantage of the technology being suitable for direct integration with microsystems and integrated circuit microelectronics.
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streaming phenomena in microdroplets induced by rayleigh surface Acoustic Wave
2011Co-Authors: M Alghane, Yifan Li, Yong Qing Fu, Baixin Chen, M P Y Desmulliez, A.j. WaltonAbstract:This paper reports the numerical simulation and experimental characterization of three-dimensional Acoustic streaming behavior of a liquiddroplet subjected to a Rayleigh surface Acoustic Wave. The streaming behavior of the droplet was studied as a function of radio-frequency (RF) power, aperture of the interdigitated transducer, and size of the liquiddroplet. The hydrodynamic flow field within the droplet was determined by solving the laminar incompressible Navier–Stoke’s equations. The numerical and experimental results are shown to be in good agreement over the range of parameters examined. The ratios of the position of butterfly central line (axis of rotation) to radius of the droplet are demonstrated to be fairly constant for moderate droplet volumes and to vary by less than 12% at large droplet volumes. Besides that, an increase in the RF power and a decrease in the droplet size result in an increased surface Acoustic Wave(SAW) streaming velocity. The numerical results also suggest that a maximum streaming velocity is achieved when the SAW width is approximately half of the droplet radius.
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recent developments on zno films for Acoustic Wave based bio sensing and microfluidic applications a review
2010Co-Authors: A.j. Walton, Jikui Luo, A J Flewitt, Gerard H Markx, W I MilneAbstract:Recent developments on the preparation and application of ZnO films for Acoustic Wave-based microfluidics and biosensors are reviewed in this paper. High quality and strongly textured ZnO thin films can be prepared using many technologies, among which RF magnetron sputtering is most commonly used. This paper reviews the deposition of ZnO film and summarizes the factors influencing the microstructure, texture and piezoelectric properties of deposited ZnO films. ZnO Acoustic Wave devices can be successfully used as biosensors, based on the biomolecule recognition using highly sensitive shear horizontal and Love-Wave surface Acoustic Waves, as well as film bulk Acoustic resonator devices. The Acoustic Wave generated on the ZnO Acoustic devices can induce significant Acoustic streaming, small scale fluid mixing, pumping, ejection and atomization, depending on the Wave mode, amplitude and surface condition. The potential to fabricate an integrated lab-on-a-chip diagnostic system based on these ZnO Acoustic Wave technologies is also discussed.
James Friend - One of the best experts on this subject based on the ideXlab platform.
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surface Acoustic Wave microfluidics
2014Co-Authors: Leslie Y Yeo, James FriendAbstract:Fluid manipulations at the microscale and beyond are powerfully enabled through the use of 10–1,000-MHz Acoustic Waves. A superior alternative in many cases to other microfluidic actuation techniques, such high-frequency Acoustics is almost universally produced by surface Acoustic Wave devices that employ electromechanical transduction in wafer-scale or thin-film piezoelectric media to generate the kinetic energy needed to transport and manipulate fluids placed in adjacent microfluidic structures. These Waves are responsible for a diverse range of complex fluid transport phenomena—from interfacial fluid vibration and drop and confined fluid transport to jetting and atomization—underlying a flourishing research literature spanning fundamental fluid physics to chip-scale engineering applications. We highlight some of this literature to provide the reader with a historical basis, routes for more detailed study, and an impression of the field's future directions.
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the dynamics of surface Acoustic Wave driven scaffold cell seeding
2009Co-Authors: Melanie Bok, Leslie Y Yeo, James FriendAbstract:Flow visualization using fluorescent microparticles and cell viability investigations are carried out to examine the mechanisms by which cells are seeded into scaffolds driven by surface Acoustic Waves. The former consists of observing both the external flow prior to the entry of the suspension into the scaffold and the internal flow within the scaffold pores. The latter involves micro-CT (computed tomography) scans of the particle distributions within the seeded scaffolds and visual and quantitative methods to examine the morphology and proliferation ability of the irradiated cells. The results of these investigations elucidate the mechanisms by which particles are seeded, and hence provide valuable information that form the basis for optimizing this recently discovered method for rapid, efficient, and uniform scaffold cell seeding. Yeast cells are observed to maintain their size and morphology as well as their proliferation ability over 14 days after they are irradiated. The mammalian primary osteoblast cells tested also show little difference in their viability when exposed to the surface Acoustic Wave irradiation compared to a control set. Together, these provide initial feasibility results that demonstrate the surface Acoustic Wave technology as a viable seeding method without risk of denaturing the cells.
Jikui Luo - One of the best experts on this subject based on the ideXlab platform.
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high frequency microfluidic performance of linbo3 and zno surface Acoustic Wave devices
2014Co-Authors: Yuanjun Guo, Jikui Luo, Jian Zhou, A.j. WaltonAbstract:Rayleigh surface Acoustic Wave (SAW) devices based on 128° YX LiNbO3 and ZnO/Si substrates with different resonant frequencies from ∼62 MHz to ∼275 MHz were fabricated and characterized. Effects of SAW frequency and power on microfluidic performance (including streaming, pumping, and jetting) were investigated. SAW excitation frequency influenced the SAW attenuation length and hence the Acoustic energy absorbed by the liquid. At higher frequencies (e.g., above 100 MHz), the SAW dissipated into liquid decays more rapidly with much shorter decay lengths. Increasing the radio frequency (RF) frequencies of the devices resulted in an increased power threshold for streaming, pumping, and especially jetting, which is attributed to an increased absorption rate of Acoustic Wave energy. ZnO SAW devices could achieve similar streaming, pumping, and jetting effects as well as frequency effect, although the SAW signals are relatively weaker.
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recent developments on zno films for Acoustic Wave based bio sensing and microfluidic applications a review
2010Co-Authors: A.j. Walton, Jikui Luo, A J Flewitt, Gerard H Markx, W I MilneAbstract:Recent developments on the preparation and application of ZnO films for Acoustic Wave-based microfluidics and biosensors are reviewed in this paper. High quality and strongly textured ZnO thin films can be prepared using many technologies, among which RF magnetron sputtering is most commonly used. This paper reviews the deposition of ZnO film and summarizes the factors influencing the microstructure, texture and piezoelectric properties of deposited ZnO films. ZnO Acoustic Wave devices can be successfully used as biosensors, based on the biomolecule recognition using highly sensitive shear horizontal and Love-Wave surface Acoustic Waves, as well as film bulk Acoustic resonator devices. The Acoustic Wave generated on the ZnO Acoustic devices can induce significant Acoustic streaming, small scale fluid mixing, pumping, ejection and atomization, depending on the Wave mode, amplitude and surface condition. The potential to fabricate an integrated lab-on-a-chip diagnostic system based on these ZnO Acoustic Wave technologies is also discussed.
David A Weitz - One of the best experts on this subject based on the ideXlab platform.
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Surface Acoustic Wave actuated cell sorting (SAWACS)
2010Co-Authors: T. Franke, S. Braunmüller, Achim Wixforth, L. Schmid, David A WeitzAbstract:We describe a novel microfluidic cell sorter which operates in continuous flow at high sorting rates. The device is based on a surface Acoustic Wave cell-sorting scheme and combines many advantages of fluorescence activated cell sorting (FACS) and fluorescence activated droplet sorting (FADS) in microfluidic channels. It is fully integrated on a PDMS device, and allows fast electronic control of cell diversion. We direct cells by Acoustic streaming excited by a surface Acoustic Wave which deflects the fluid independently of the contrast in material properties of deflected objects and the continuous phase; thus the device underlying principle works without additional enhancement of the sorting by prior labelling of the cells with responsive markers such as magnetic or polarizable beads. Single cells are sorted directly from bulk media at rates as fast as several kHz without prior encapsulation into liquid droplet compartments as in traditional FACS. We have successfully directed HaCaT cells (human keratinocytes), fibroblasts from mice and MV3 melanoma cells. The low shear forces of this sorting method ensure that cells survive after sorting.
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surface Acoustic Wave saw directed droplet flow in microfluidics for pdms devices
2009Co-Authors: Thomas Franke, David A Weitz, Adam R Abate, Achim WixforthAbstract:We direct the motion of droplets in microfluidic channels using a surface Acoustic Wave device. This method allows individual drops to be directed along separate microchannel paths at high volume flow rates, which is useful for droplet sorting.
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diffusing Acoustic Wave spectroscopy
2002Co-Authors: David A Weitz, Michael L Cowan, I P Jones, J H PageAbstract:We have developed a technique in ultrasonic correlation spectroscopy called diffusing Acoustic Wave spectroscopy (DAWS). In this technique, the motion of the scatterers (e.g., particles or inclusions) is determined from the temporal fluctuations of multiply scattered sound. In DAWS, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the autocorrelation function of the temporal field fluctuations to be related to the dynamics of the multiply scattering medium. The expressions relating the temporal field autocorrelation function to the motion of the scatterers are derived, focusing on the types of correlated motions that are most likely to be encountered in Acoustic measurements. The power of this technique is illustrated with ultrasonic data on fluidized suspensions of particles, where DAWS provides a sensitive measure of the local relative velocity and strain rate of the suspended particles over a wide range of time and length scales. In addition, when combined with the measurements of the rms velocity of the particles using dynamic sound scattering, we show that DAWS can be used to determine the spatial extent of the correlations in the particle velocities, thus indirectly measuring the particle velocity correlation function. Potential applications of diffusing Acoustic Wave spectroscopy are quite far reaching, ranging from the ultrasonic nondestructive evaluation of the dynamics of inhomogeneous materials to geophysical studies of mesoscopic phenomena in seismology.
Yong Qing Fu - One of the best experts on this subject based on the ideXlab platform.
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surface Acoustic Wave nebulization on nanocrystalline zno film
2012Co-Authors: Yong Qing Fu, Yifan Li, Frank Placido, Chao Zhao, A.j. WaltonAbstract:Surface Acoustic Wave(SAW) nebulization/atomization has been realised on thin ZnOfilm based SAWdevices. The surface Acoustic Wave nebulization (SAWN) process has been observed to produce significant mist generation and ejected satellitedroplets. By modifying the geometry of the interdigitated transducers to reduce the Wavelengths from 400 μm to 120 μm, higher frequency SAWN has been achieved by increasing radio frequency driving frequencies from 11.8 MHz to 37.2 MHz, respectively. Compared with the commonly used LiNbO3 SAWN devices,ZnOfilmdevices exhibit better thermal dissipation, and to date, they have shown no susceptibility to substrate failure during fabrication or operation. They also have the added advantage of the technology being suitable for direct integration with microsystems and integrated circuit microelectronics.
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streaming phenomena in microdroplets induced by rayleigh surface Acoustic Wave
2011Co-Authors: M Alghane, Yifan Li, Yong Qing Fu, Baixin Chen, M P Y Desmulliez, A.j. WaltonAbstract:This paper reports the numerical simulation and experimental characterization of three-dimensional Acoustic streaming behavior of a liquiddroplet subjected to a Rayleigh surface Acoustic Wave. The streaming behavior of the droplet was studied as a function of radio-frequency (RF) power, aperture of the interdigitated transducer, and size of the liquiddroplet. The hydrodynamic flow field within the droplet was determined by solving the laminar incompressible Navier–Stoke’s equations. The numerical and experimental results are shown to be in good agreement over the range of parameters examined. The ratios of the position of butterfly central line (axis of rotation) to radius of the droplet are demonstrated to be fairly constant for moderate droplet volumes and to vary by less than 12% at large droplet volumes. Besides that, an increase in the RF power and a decrease in the droplet size result in an increased surface Acoustic Wave(SAW) streaming velocity. The numerical results also suggest that a maximum streaming velocity is achieved when the SAW width is approximately half of the droplet radius.
