| 1. |
- Ley, M. W H, et al.
(author)
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Modeling and experiments of acoustic trapping forces in a small glass capillary
- 2016
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In: 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016. - 9780979806490 ; , s. 711-712
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Conference paper (peer-reviewed)abstract
- In this work we present theoretical modeling and additional experiments to characterize noncontact acoustic trapping in a small glass capillary. We provide numerical 3D-simulations that captures several key features of the experiment.
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| 2. |
- Antfolk, Maria, et al.
(author)
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Focusing of sub-micrometer particles and bacteria enabled by two-dimensional acoustophoresis.
- 2014
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In: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189. ; 14:15, s. 2791-2799
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Journal article (peer-reviewed)abstract
- Handling of sub-micrometer bioparticles such as bacteria are becoming increasingly important in the biomedical field and in environmental and food analysis. As a result, there is an increased need for less labor-intensive and time-consuming handling methods. Here, an acoustophoresis-based microfluidic chip that uses ultrasound to focus sub-micrometer particles and bacteria, is presented. The ability to focus sub-micrometer bioparticles in a standing one-dimensional acoustic wave is generally limited by the acoustic-streaming-induced drag force, which becomes increasingly significant the smaller the particles are. By using two-dimensional acoustic focusing, i.e. focusing of the sub-micrometer particles both horizontally and vertically in the cross section of a microchannel, the acoustic streaming velocity field can be altered to allow focusing. Here, the focusability of E. coli and polystyrene particles as small as 0.5 μm in diameter in microchannels of square or rectangular cross sections, is demonstrated. Numerical analysis was used to determine generic transverse particle trajectories in the channels, which revealed spiral-shaped trajectories of the sub-micrometer particles towards the center of the microchannel; this was also confirmed by experimental observations. The ability to focus and enrich bacteria and other sub-micrometer bioparticles using acoustophoresis opens the research field to new microbiological applications.
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| 3. |
- Augustsson, P., et al.
(author)
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Acoustophoretic manipulation of sub-micron objects enabled by density gradients
- 2016
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In: 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016. - 9780979806490 ; , s. 158-159
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Conference paper (peer-reviewed)abstract
- Direct and precise manipulation of sub-micron particles such as bacteria, platelets, organelles, microvesicles, exosomes or virus particles is challenging. We describe for the first time how acoustic streaming in the bulk can be efficiently reduced by introducing a density or compressibility gradient and that this enables focusing of 500-nm-diameter particles in a standard acoustophoresis channel.
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| 4. |
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| 5. |
- Garofalo, F., et al.
(author)
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Optimal design of silicon-based chips for piezo-induced ultrasound resonances in embedded microchannels
- 2015
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In: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 70, s. 50-54
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Conference paper (peer-reviewed)abstract
- We present a variational formulation of the governing equations and introduce global indicators to describe the behavior of acoustofluidic devices driven at resonance frequencies by means of a piezoelectric transducer. The individuation of the correct Lagrangian densities for the different parts constituting the device (the piezo transducer, the silicon walls, the fluid-filled microchannel, and the glass lid) allows for the introduction of the weak formulation used in the finite element discretization of the equations describing the system in its oscillatory regime. Additionally, the knowledge of the Lagrangian density leads to the derivation of the correct structure of the Hamiltonian density, i.e. the energy density, which is important for the quantification of the energy content of the whole system and its individual parts. Specifically, the energy content of the embedded microchannel is quantified by means of the acoustofluidic yield η defined as the ratio between the energy in the channel and the total energy. From the standpoint of acoustophoretic application, the introduction of the acoustophoretic mean orientation allows us to identify the frequencies for which an acoustophoretic effect, i.e. the lateral motion of particle dragged by the axial main flow, is particularly strong. Finally, the connection between the mechanical and electrical degrees of freedom of the system is addressed. This is important for proper determination of the dissipated power, and it may lead to the detection of resonance states by means of purely electrical measurements. Numerical simulations and preliminary experimental results show some features of the model introduced.
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| 6. |
- Hagsater, S. M., et al.
(author)
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Acoustic resonances in straight micro channels: Beyond the 1D-approximation
- 2008
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In: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 8:7, s. 1178-1184
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Journal article (peer-reviewed)abstract
- Acoustic actuation can be used to perform several tasks in microfluidic systems. In this paper, we investigate an acoustic separator through micro-PIV analysis in stop-flow mode and numerical simulations, and a good agreement between the two is found. Moreover, we demonstrate that it is not sufficient only to characterize devices in flow-through mode, since in these systems much different resonant patterns can result in similarly looking band formations. Furthermore, we conclude that extended 1D approximations of the acoustic radiation force are inadvisable, and instead, a 2D model is preferred. The results presented here provide valuable insight into the nature and functionality of acoustic microdevices, and should be useful in the interpretation and understanding of the same.
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| 7. |
- Iranmanesh, Ida, et al.
(author)
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Magnitude and variance of acoustic energy density in microchannel acoustophoresis : Comparison between single-frequency and frequency-modulated actuation
- 2013
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In: 17th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2013. - 9781632666246 ; , s. 1400-1402
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Conference paper (peer-reviewed)abstract
- Using a novel light-intensity method, we quantify for the first time the magnitude and spatial variance in acoustic energy density along a microchannel during acoustophoretic focusing of particles with frequency-modulated ultrasound. We compare the distribution in energy density between single-frequency (SF) and frequency-modulation (FM) actuation along the microchannel. In addition, we analyze the field uniformity for the two actuation approaches (SF and FM) by measuring the deviation of the final particle pattern from an ideal straight line. We conclude that the magnitude of the energy density for FM actuation is of the same order of magnitude as for SF actuation, but with much less spatial variance.
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| 8. |
- Iranmanesh, Ida Sadat, et al.
(author)
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Tunable-angle wedge transducer for improved acoustophoretic control in a microfluidic chip
- 2013
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 23:10, s. 105002-
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Journal article (peer-reviewed)abstract
- We present a tunable-angle wedge ultrasound transducer for improved control of microparticle acoustophoresis in a microfluidic chip. The transducer is investigated by analyzing the pattern of aligned particles and induced acoustic energy density while varying the transducer geometry, transducer coupling angle, and transducer actuation method (single-frequency actuation or frequency-modulation actuation). The energy-density analysis is based on measuring the transmitted light intensity through a microfluidic channel filled with a suspension of 5 mu m diameter beads and the results with the tunable-angle transducer are compared with the results from actuation by a standard planar transducer in order to decouple the influence from change in coupling angle and change in transducer geometry. We find in this work that the transducer coupling angle is the more important parameter compared to the concomitant change in geometry and that the coupling angle may be used as an additional tuning parameter for improved acoustophoretic control with single-frequency actuation. Further, we find that frequency-modulation actuation is suitable for diminishing such tuning effects and that it is a robust method to produce uniform particle patterns with average acoustic energy densities comparable to those obtained using single-frequency actuation.
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| 9. |
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| 10. |
- Muller, P. B., et al.
(author)
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Ultrasound-induced acoustophoretic motion of microparticles in three dimensions
- 2013
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In: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 88:2
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Journal article (peer-reviewed)abstract
- We derive analytical expressions for the three-dimensional (3D) acoustophoretic motion of spherical microparticles in rectangular microchannels. The motion is generated by the acoustic radiation force and the acoustic streaming-induced drag force. In contrast to the classical theory of Rayleigh streaming in shallow, infinite, parallel-plate channels, our theory does include the effect of the microchannel sidewalls. The resulting predictions agree well with numerics and experimental measurements of the acoustophoretic motion of polystyrene spheres with nominal diameters of 0.537 and 5.33 mu m. The 3D particle motion was recorded using astigmatism particle tracking velocimetry under controlled thermal and acoustic conditions in a long, straight, rectangular microchannel actuated in one of its transverse standing ultrasound-wave resonance modes with one or two half-wavelengths. The acoustic energy density is calibrated in situ based on measurements of the radiation dominated motion of large 5-mu m-diameter particles, allowing for quantitative comparison between theoretical predictions and measurements of the streaming-induced motion of small 0.5-mu m-diameter particles.
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