Improved positioning and detectability of microparticles in droplet microfluidics using two-dimensional acoustophoresis

Ohlin, Mathias; Fornell, Anna; Bruus, Henrik

doi:10.1088/1361-6439/aa7967

Cited by 10 publications

(6 citation statements)

References 38 publications

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“…In this work acoustic resonance was only set in the y-direction, thus the particles were only focused in that direction. However, it would be possible to focus the particles also in the z-direction 38 by using either a square microfluidic channel or by using a second transducer matched to the channel height.…”

Section: Resultsmentioning

confidence: 99%

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Acoustic focusing of beads and cells in hydrogel droplets

Fornell

Pohlit

Shi

2021

Sci Rep

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The generation of hydrogel droplets using droplet microfluidics has emerged as a powerful tool with many applications in biology and medicine. Here, a microfluidic system to control the position of particles (beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves is presented. The chip consisted of a droplet generator and a 380 µm wide acoustic focusing channel. Droplets comprising hydrogel precursor solution (polyethylene glycol tetraacrylate or a combination of polyethylene glycol tetraacrylate and gelatine methacrylate), photoinitiator and particles were generated. The droplets passed along the acoustic focusing channel where a half wavelength acoustic standing wave field was generated, and the particles were focused to the centre line of the droplets (i.e. the pressure nodal line) by the acoustic force. The droplets were cross-linked by exposure to UV-light, freezing the particles in their positions. With the acoustics applied, 89 ± 19% of the particles (polystyrene beads, 10 µm diameter) were positioned in an area ± 10% from the centre line. As proof-of-principle for biological particles, astrocytes were focused in hydrogel droplets using the same principle. The viability of the astrocytes after 7 days in culture was 72 ± 22% when exposed to the acoustic focusing compared with 70 ± 19% for samples not exposed to the acoustic focusing. This technology provides a platform to control the spatial position of bioparticles in hydrogel droplets, and opens up for the generation of more complex biological hydrogel structures.

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Section: Resultsmentioning

confidence: 99%

“…The microfluidic channels were etched on a 500 µm thin silicon wafer using deep reactive ion etching according to a standard protocol 38 . Both the droplet generator channels and the acoustic focusing channel were 380 µm by 100 µm (width × height).…”

Section: Methodsmentioning

confidence: 99%

Acoustic focusing of beads and cells in hydrogel droplets

Fornell

Pohlit

Shi

2021

Sci Rep

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“…Therefore, a microfluidic platform that can efficiently sort and enrich cell‐laden droplets is particularly important during drug screening. [ 22,23 ]…”

Section: Introductionmentioning

confidence: 99%

Acoustofluidic Droplet Sorter Based on Single Phase Focused Transducers

Zhong

Yang

Ugolini

et al. 2021

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Droplet microfluidics has revolutionized the biomedical and drug development fields by allowing for independent microenvironments to conduct drug screening at the single cell level. However, current microfluidic sorting devices suffer from drawbacks such as high voltage requirements (e.g., >200 Vpp), low biocompatibility, and/or low throughput. In this article, a single‐phase focused transducer (SPFT)‐based acoustofluidic chip is introduced, which outperforms many microfluidic droplet sorting devices through high energy transmission efficiency, high accuracy, and high biocompatibility. The SPFT‐based sorter can be driven with an input power lower than 20 Vpp and maintain a postsorting cell viability of 93.5%. The SPFT sorter can achieve a throughput over 1000 events per second and a sorting purity up to 99.2%. The SPFT sorter is utilized here for the screening of doxorubicin cytotoxicity on cancer and noncancer cells, proving its drug screening capability. Overall, the SPFT droplet sorting device shows great potential for fast, precise, and biocompatible drug screening.

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“…Therefore, the channel should be fabricated in a material with high acoustic impedance to allow for the build-up of a strong acoustic standing wave field in the channel. Generally, bulk acoustic wave devices are fabricated in silicon [6,7] or glass [8], both having much higher acoustic impedance (19.8 MRayl and 12.6 MRayl, respectively) than water (1.5 MRayl) [5]. Microfabrication of silicon and glass is commonly done by wet-or dry-etching.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Silicon Microfluidic Chips for Acoustic Particle Focusing Using Direct Laser Writing

et al. 2020

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We have developed a fast and simple method for fabricating microfluidic channels in silicon using direct laser writing. The laser microfabrication process was optimised to generate microfluidic channels with vertical walls suitable for acoustic particle focusing by bulk acoustic waves. The width of the acoustic resonance channel was designed to be 380 µm, branching into a trifurcation with 127 µm wide side outlet channels. The optimised settings used to make the microfluidic channels were 50% laser radiation power, 10 kHz pulse frequency and 35 passes. With these settings, six chips could be ablated in 5 h. The microfluidic channels were sealed with a glass wafer using adhesive bonding, diced into individual chips, and a piezoelectric transducer was glued to each chip. With acoustic actuation at 2.03 MHz a half wavelength resonance mode was generated in the microfluidic channel, and polystyrene microparticles (10 µm diameter) were focused along the centre-line of the channel. The presented fabrication process is especially interesting for research purposes as it opens up for rapid prototyping of silicon-glass microfluidic chips for acoustofluidic applications.

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Improved positioning and detectability of microparticles in droplet microfluidics using two-dimensional acoustophoresis

Cited by 10 publications

References 38 publications

Acoustic focusing of beads and cells in hydrogel droplets

Acoustic focusing of beads and cells in hydrogel droplets

Acoustofluidic Droplet Sorter Based on Single Phase Focused Transducers

Fabrication of Silicon Microfluidic Chips for Acoustic Particle Focusing Using Direct Laser Writing

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