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| 2. |
- Baasch, Thierry, et al.
(författare)
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Gap Distance Between Pearl Chains in Acoustic Manipulation
- 2022
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Ingår i: Physical Review Applied. - 2331-7019. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a theory to compute the stable gap (interparticle) distance between particle chains collected in the pressure node of an acoustic standing wave. The primary and secondary acoustic radiation forces are the two competing forces that act on the particles during the particle chain formation. The stable equilibrium distance between two chains is reached when both forces are in balance. Most interestingly, the density scattering coefficient appears to the second power in the theoretical prediction of the gap distance, indicating that the particle-chain formation occurs for both particles heavier than the surrounding medium and, notably, also for buoyant particles. Experimentally, the gap distance is evaluated for several different media and particle material combinations and the particle-chain formation is observed for both buoyantparticles and particles heavier than the surrounding medium. The theory agrees well with experiments in the cases where the material properties of the medium and the particles are well known.
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| 3. |
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| 4. |
- Edthofer, Alexander, et al.
(författare)
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Acoustofluidic Properties of Polystyrene Microparticles
- 2023
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Ingår i: Analytical Chemistry. - 0003-2700. ; 95:27, s. 10346-10352
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Tidskriftsartikel (refereegranskat)abstract
- Acoustophoresis has become a powerful tool to separate microparticles and cells, based on their material and biophysical properties, and is gaining popularity in clinical and biomedical research. One major application of acoustophoresis is to measure the compressibility of cells and small organisms, which is related to their contents. The cell compressibility can be extracted from the acoustic mobility, which is the main output of acoustic migration experiments, if the material properties and sizes of reference particles, the size of the cells, and the surrounding medium are known. Accurate methods to measure and calibrate the acoustic energy density in acoustophoresis systems are therefore critical. In this Perspective, polystyrene microparticles have become the most commonly used reference particles in acoustophoresis, due to their similar biophysical properties to cells. We utilized a two-step focusing method to measure the relative acoustic mobility of polystyrene beads of various sizes and colors and present a quantitative analysis of the variation in acousto-mechanical properties of polystyrene microparticles, showing a large spread in their material properties. A variation of more than 25% between different particle types was found. Thus, care is required when relying on polystyrene particles as a reference when characterizing acoustofluidics systems or acousto-mechanical properties of cells.
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| 5. |
- Fornell, Anna, et al.
(författare)
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Binary acoustic trapping in a glass capillary
- 2021
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Ingår i: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 54:35
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic trapping is a useful method for handling biological samples in microfluidic systems. The aim of this work is twofold: first to investigate the physics behind acoustic trapping in a glass capillary and secondly to perform binary acoustic trapping. The latter is achieved by increasing the density of the fluid in the trapping channel. The trapping device consisted of a glass capillary with a rectangular inner cross-section (height 200 µm × width 2000 µm) equipped with a small piezoelectric transducer. The piezoelectric transducer was actuated at 4 MHz to generate a localised half-wavelength acoustic standing-wave-field in the capillary, comprising of a pressure field and a velocity field. Under acoustic actuation, only particles with higher density than the fluid, i.e. having a positive dipole scattering coefficient, were trapped in the flow direction. The numerical and analytical modelling of the system show that the trapping force which retains the particles against the flow depends only on the dipole scattering coefficient in the pressure nodal plane of the acoustic field. The analytical model also reveals that the retention force is proportional to the dipole scattering coefficient, which agrees with our experimental findings. Next, we showed that in a mixture of melamine particles and polystyrene particles in a high-density fluid it is possible to selectively trap melamine particles, since melamine particles have higher density than polystyrene particles.
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| 6. |
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| 7. |
- Havers, Megan, et al.
(författare)
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Silica seed particles improve the efficiency and throughput of nanoparticle acoustic trapping
- 2024
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Ingår i: Physical Review Applied. - 2331-7019. ; 21:3
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Tidskriftsartikel (refereegranskat)abstract
- Silica has rarely been used as a seed particle material in acoustic trapping of nanoparticles. Here we use fluorescent nanoparticles, which are frequently used as a model system, to demonstrate that throughput and nanoparticle trapping efficiency can be improved by using silica seed particles as opposed to traditionally used polystyrene seed particles. The 10 times larger dipole scattering coefficient of silica seed particles compared with polystyrene seed particles in water leads to a higher retention force against fluid flow and thus enables higher throughput. Seed particles retained at an actuation voltage of approximately 10 V p.p. can withstand flow rates up to 2100 ± 200 μl/min for silica and 200 ± 50 μl/min for polystyrene. Furthermore, silica is found to be 40%-2000% more efficient (number of trapped nanoparticles as measured by fluorescent intensity) than polystyrene seed particles in trapping 270-nm polystyrene nanoparticles from suspensions of 1010-1011 particles/ml. Moreover, after enriching nanoparticles into a silica seed particle cluster, the washing flow rate can be increased from 30 μl/min to 200 μl/min (the flow rate at which polystyrene clusters are unstable), halving the total sample processing time without losing the silica seed particle cluster or compromising the nanoparticle trapping efficiency. Thus, material properties (particularly density) of the seed particles are critical to both nanoparticle trapping efficiency and throughput.
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| 8. |
- Qiu, Wei, et al.
(författare)
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Enhancement of Acoustic Energy Density in Bulk-Wave-Acoustophoresis Devices Using Side Actuation
- 2022
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Ingår i: Physical Review Applied. - 2331-7019. ; 17:4
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Tidskriftsartikel (refereegranskat)abstract
- A high acoustic energy density is required in the acoustic resonator to increase the throughput of acoustophoresis devices. In this study, through both experiments and numerical simulations, we find that the energy density in bulk-wave-acoustophoresis devices can be enhanced by actuating the device from the side. Based on qualitative free-flow focusing experiments, side actuation shows clear superiority to bottom actuation under various input powers and flow rates. Quantitative measurements using confocal microparticle image velocimetry confirm an increase by a factor of 4 in energy density using side actuation. Numerical simulations reveal that side actuation leads to significant symmetry breaking, which accounts for strong acoustic fields in the channel, and the device energy-conversion efficiency using side actuation is also higher than that using bottom actuation for different device aspect ratios. Submicrometer particle focusing is performed using an acoustophoresis device with side actuation and more than 90% of 500-nm-diameter particles are focused under a total flow rate of 30 μl/min at an input power of 235 mW, achieved without using a power amplifier.
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| 9. |
- Ugawa, Masashi, et al.
(författare)
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Reduced acoustic resonator dimensions improve focusing efficiency of bacteria and submicron particles
- 2022
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 147:2, s. 274-281
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we demonstrate an acoustofluidic device that enables single-file focusing of submicron particles and bacteria using a two-dimensional (2D) acoustic standing wave. The device consists of a 100 μm × 100 μm square channel that supports 2D particle focusing in the channel center at an actuation frequency of 7.39 MHz. This higher actuation frequency compared with conventional bulk acoustic systems enables radiation-force-dominant motion of submicron particles and overcomes the classical size limitation (≈2 μm) of acoustic focusing. We present acoustic radiation force-based focusing of particles with diameters less than 0.5 μm at a flow rate of 12 μL min−1, and 1.33 μm particles at flow rates up to 80 μL min−1. The device focused 0.25 μm particles by the 2D acoustic radiation force while undergoing a channel cross-section centered, single-vortex acoustic streaming. A suspension of bacteria was also investigated to evaluate the biological relevance of the device, which demonstrated the alignment of bacteria in the channel at aflow rate of up to 20 μL min−1. The developed acoustofluidic device can align submicron particles within a narrow flow stream in a highly robust manner, validating its use as a flow-through focusing chamber to perform high-throughput and accurate flow cytometry of submicron objects
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| 10. |
- Undvall, Eva, et al.
(författare)
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Inertia-Induced Breakdown of Acoustic Sorting Efficiency at High Flow Rates
- 2022
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Ingår i: Physical Review Applied. - 2331-7019. ; 17:3
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Tidskriftsartikel (refereegranskat)abstract
- The clinical utility of microfluidic techniques is often hampered by an unsatisfying sample throughput. Here, the effect of inertial forces on acoustofluidic particle sorting at high sample throughputs is investigated experimentally and theoretically. Polystyrene particles are acoustically prefocused to obtain precise trajectories. At increased flow rates it is observed that the particle stream is displaced towards the channel center, and above specific flow settings the particles spill over into the center outlet. This effect, coined the spillover effect, illustrates the complex interplay of viscous and inertial forces inside the microchannel. The effect is due to increased bending of the separatrices at the inlet and outlets and not due to the wall-lift force. The impact of the spillover effect on the separation of two different-sized particles is subsequently studied. Efficient sorting is done for subcritical splitting ratios and flow rates, but for close to critical settings or beyond, there is a breakdown of the acoustofluidic separation.
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