On the acoustically induced fluid flow in particle separation systems employing standing surface acoustic waves – Part II

Sachs, Sebastian; Cierpka, Christian; König, Jörg

doi:10.1039/d2lc00106c

Cited by 8 publications

(3 citation statements)

References 66 publications

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“…Although only 0.1 % of the detected particles were found near the channel floor (z/λ BAW < 0.5) without the influence of the acoustoelectric wave field, this proportion increased to 46.5 % when the sSAW was activated. This phenomenon is strongly affected by the acoustically induced fluid flow, which is discussed below based on numerical simulations and in detail in our previous studies [86,87].…”

Section: Methodsmentioning

confidence: 83%

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Interplay of acoustophoresis and dielectrophoresis in a standing surface acoustic wave field: from spherical to non-spherical particles

Sachs,

Schreier,

Brand

et al. 2024

Preprint

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Standing surface acoustic waves (sSAW) emerged as a flexible tool for precise manipulation of spherical and non-spherical objects in Lab-on-a-Chip devices. While the manipulation of suspended particles and cells in acoustofluidic devices is mostly dominated by acoustic forces due to acoustic scattering and the acoustically induced fluid flow, surface acoustic waves are inherently linked to an inhomogeneous electric field. The superimposed effects of dielectrophoretic forces and torques on polarizable particles are less explored in microfluidics using sSAW. In this study, a thorough analysis of the physical interplay of acoustophoresis and dielectrophoresis aims to bridge this gap. In comprehensive experiments, the dielectrophoretic impact on the behavior of spherical and non-spherical particles is distinguished by screening the electric field of the sSAW inside the micro channel locally. As a result, particles are forced into trapping locations across the entire channel height. However, the height position close to the bottom differs between the screened and non-screened region. Regardless of the shape of the particles used in this study, particles are forced towards the bottom at the region with screening, while being levitated at regions without screening. This indicates uniquely the influence of the electric field, existing in close vicinity to the substrate surface only. Furthermore, the unintuitive preferred orientation of prolate spheroids perpendicular to the pressure nodes of the sSAW recently reported, has been confirmed considering the influence of the electric field. Based on a three-dimensional numerical model established, this orientation results not only due to the acoustic torque but is also caused by the dielectrophoretic torque, which complement each other. The experimental and numerical findings are in excellent agreement and provide deep insights into the underlying physical mechanisms responsible for patterning and orientation of the particles.

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Section: Methodsmentioning

confidence: 83%

“…This might be caused by acoustothermal effects and acoustically induced vortex structures forming at the beginning of the sSAW field, which influence the initial particle positions (see Fig. S8, [87]). Both effects are more pronounced with increasing electrical power and potentially alter the preferred positions of the non-spherical particles.…”

Section: Methodsmentioning

confidence: 99%

Interplay of acoustophoresis and dielectrophoresis in a standing surface acoustic wave field: from spherical to non-spherical particles

Sachs,

Schreier,

Brand

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

“…Obviously, the explanations given to date, considering the influence of the ARF solely, do not hold generally. Meanwhile, in several numerical and experimental investigations of the acoustic streaming effect, a fluid flow with a considerable velocity was reported, [28][29][30] which may allow particles to be displaced from their predicted trapping locations. However, measurements of the fluid flow will be required to verify it finally.…”

Section: Resultsmentioning

confidence: 99%

From rectangular to diamond shape: on the three-dimensional and size-dependent transformation of patterns formed by single particles trapped in microfluidic acoustic tweezers

et al. 2023

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Particle detection and size recognition based on defocused particle images: a comparison of a deterministic algorithm and a deep neural network

et al. 2023

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The systematic manipulation of components of multimodal particle solutions is a key for the design of modern industrial products and pharmaceuticals with highly customized properties. In order to optimize innovative particle separation devices on microfluidic scales, a particle size recognition with simultaneous volumetric position determination is essential. In the present study, the astigmatism particle tracking velocimetry is extended by a deterministic algorithm and a deep neural network (DNN) to include size classification of particles of multimodal size distribution. Without any adaptation of the existing measurement setup, a reliable classification of bimodal particle solutions in the size range of $$1.14~\upmu \hbox {m}$$ 1.14 μ m –$$5.03~\upmu \hbox {m}$$ 5.03 μ m is demonstrated with a precision of up to 99.9 %. Concurrently, the high detection rate of the particles, suspended in a laminar fluid flow, is quantified by a recall of 99.0 %. By extracting particle images from the experimentally acquired images and placing them on a synthetic background, semi-synthetic images with consistent ground truth are generated. These contain labeled overlapping particle images that are correctly detected and classified by the DNN. The study is complemented by employing the presented algorithms for simultaneous size recognition of up to four particle species with a particle diameter in between $$1.14~\upmu \hbox {m}$$ 1.14 μ m and $$5.03~\upmu \hbox {m}$$ 5.03 μ m . With the very high precision of up to 99.3 % at a recall of 94.8 %, the applicability to classify multimodal particle mixtures even in dense solutions is confirmed. The present contribution thus paves the way for quantitative evaluation of microfluidic separation and mixing processes.

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On the acoustically induced fluid flow in particle separation systems employing standing surface acoustic waves – Part II

Abstract: Experimental analysis of the acoustically induced fluid flow in the outer regions of a standing surface acoustic wave (sSAW) for varying sSAW wavelength, channel height and electrical power.

Cited by 8 publications

References 66 publications

Interplay of acoustophoresis and dielectrophoresis in a standing surface acoustic wave field: from spherical to non-spherical particles

Interplay of acoustophoresis and dielectrophoresis in a standing surface acoustic wave field: from spherical to non-spherical particles

From rectangular to diamond shape: on the three-dimensional and size-dependent transformation of patterns formed by single particles trapped in microfluidic acoustic tweezers

Particle detection and size recognition based on defocused particle images: a comparison of a deterministic algorithm and a deep neural network

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