| 21. |
- Ohlin, Mathias, et al.
(författare)
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Improved positioning and detectability of microparticles in droplet microfluidics using two-dimensional acoustophoresis
- 2017
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 27:8
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated a silicon-glass two-phase droplet microfluidic system capable of generating sub 100 μm-sized, ø = (74 ± 2) μm, spherical droplets at rates of up to hundreds of hertz. By implementing a two-dimensional (2D) acoustophoresis particle-positioning method, we show a fourfold improvement in both vertical and lateral particle positioning inside the droplets compared to unactuated operation. The efficiency of the system has been optimized by incorporating aluminum matching layers in the transducer design permitting biocompatible operational temperatures (<37 °C). Furthermore, by using acoustic actuation, (99.8 ± 0.4)% of all encapsulated microparticles can be detected compared to only (79.0 ± 5.1)% for unactuated operation. In our experiments we observed a strong ordering of the microparticles in distinct patterns within the droplet when using 2D acoustophoresis; to explain the origin of these patterns we simulated numerically the fluid flow inside the droplets and compared with the experimental findings.
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| 22. |
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| 23. |
- Ohlin, Mathias, et al.
(författare)
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Influence of acoustic streaming on ultrasonic particle manipulation in a 100-well ring-transducer microplate
- 2013
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 23:3, s. 035008-
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Tidskriftsartikel (refereegranskat)abstract
- We characterize and quantify the performance of ultrasonic particle aggregation and positioning in a 100-well microplate. We analyze the result when operating a planar ultrasonic ring transducer at different single actuation frequencies in the range 2.20-2.40 MHz, and compare with the result obtained from different schemes of frequency-modulated actuation. Compared to our previously used wedge transducer design, the ring transducer has a larger contact area facing the microplate, resulting in lower temperature increase for a given actuation voltage. Furthermore, we analyze the dynamics of acoustic streaming occurring simultaneously with the particle trapping in the wells of the microplate, and we define an adaptive ultrasonic actuation scheme for optimizing both efficiency and robustness of the method. The device is designed as a tool for ultrasound-mediated cell aggregation and positioning. This is a method for high-resolution optical characterization of time-dependent cellular processes at the level of single cells. In this paper, we demonstrate how to operate our device in order to optimize the scanning time of 3D confocal microscopy with the aim to perform high-resolution time-lapse imaging of cells or cell-cell interactions in a highly parallel manner.
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| 24. |
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| 25. |
- Ohlin, Mathias, et al.
(författare)
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Long-term acoustophoresis at 1 MPA do not compromise cell viability
- 2015
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Ingår i: MicroTAS 2015 - 19th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - : Chemical and Biological Microsystems Society. - 9780979806483 ; , s. 996-998
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Konferensbidrag (refereegranskat)abstract
- In this paper we report on the viability of cells exposed to high acoustic pressure amplitudes (>1 MPa) and long durations (one hour) in a temperature-controlled acoustofluidic microdevice. We demonstrate that A5490 lung cancer cells are not affected by the ultrasound even at pressure levels exceeding what is normally used in acoustophoresis applications, as long as the temperature and fluid streaming around the trapped cells are carefully controlled.
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| 26. |
- Ohlin, Mathias, et al.
(författare)
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Temperature-controlled MPa-pressure ultrasonic cell manipulation in a microfluidic chip
- 2015
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 15:16, s. 3341-3349
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Tidskriftsartikel (refereegranskat)abstract
- We study the temperature-independent impact on cell viability of relevant physical parameters during long-term, high-acoustic-pressure ultrasonic exposure in a microfluidic chip designed for ultrasonic-standing-wave trapping and aggregation of cells. We use a light-intensity method and 5 mum polymer beads for accurate acoustic pressure calibration before injecting cells into the device, and we monitor the viability of A549 lung cancer cells trapped during one hour in an ultrasonic standing wave with 1 MPa pressure amplitude. The microfluidic chip is actuated by a novel temperature-controlled ultrasonic transducer capable of keeping the temperature stable around 37 °C with an accuracy better than ±0.2 °C, independently on the ultrasonic power and heat produced by the system, thereby decoupling any temperature effect from other relevant effects on cells caused by the high-pressure acoustic field. We demonstrate that frequency-modulated ultrasonic actuation can produce acoustic pressures of equally high magnitudes as with single-frequency actuation, and we show that A549 lung cancer cells can be exposed to 1 MPa standing-wave acoustic pressure amplitudes for one hour without compromising cell viability. At this pressure level, we also measure the acoustic streaming induced around the trapped cell aggregate, and conclude that cell viability is not affected by streaming velocities of the order of 100 mum s(-1). Our results are important when implementing acoustophoresis methods in various clinical and biomedical applications.
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| 27. |
- Ohlin, Mathias, 1984-, et al.
(författare)
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Two-dimensional acoustic focusing of microparticles in two-phase droplet-based microfluidic systems for improved particle positioning within spherical droplets
- 2016
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Konferensbidrag (refereegranskat)abstract
- We have fabricated a silicon-glass microfluidic two-phase droplet generator capable of generating sub 100-micrometer-sized (⌀ ൌ74 μm ± 2 μm) spherical droplets at rates up to hundreds of hertz (298 Hz ± 85 Hz). Furthermore, we have implemented a two-dimensional acoustic focusing technique into the device. Here, we show that applying the focusing to 10 μm sized polystyrene particles during the droplet generation step, results in a fourfold improvement of the particle positioning (centricity) within the generated droplets compared to the unactuated control. Finally, the efficiency of the system has been optimized by incorporating aluminum matching layers in the transducer design permitting biocompatible operational temperatures (<37°C).
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| 28. |
- Ohlin, Mathias, 1984-, et al.
(författare)
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Two-dimensional acoustic focusing of microparticles in two-phase droplet-based microfluidic systems increases particle detectability
- 2016
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Ingår i: 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016. - 9780979806490 ; , s. 713-714
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Konferensbidrag (refereegranskat)abstract
- We have fabricated a silicon-glass two-phase droplet-based microfluidic system and implemented two-dimensional acoustic focusing prior to droplet generation as well as continuously throughout the whole system to increase particle detectability. Using acoustic focusing we have effectively minimized sedimentation of the encapsulated particles and thereby increased particle detectability by as much as 44% compared to unactuated operation of the system.
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| 29. |
- Ohlin, Mathias, 1984-
(författare)
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Ultrasonic Fluid and Cell Manipulation
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last decade, ultrasonic manipulation has matured into an important tool with a wide range of applications, from fundamental cell biological research to clinical and industrial implementations. The contactless nature of ultrasound makes it possible to manipulate living cells in a gentle way, e.g., for positioning, sorting, and aggregation. However, when manipulating cells using ultrasound, especially using high acoustic amplitudes, a great deal of heat can be generated. This constitutes a challenge, since the viability of cells is dependent on a stable physiological temperature around 37°C. In this Thesis we present applications of ultrasonic manipulation of fluids, particles, and cells in temperature-controlled micrometer-sized devices fabricated using well established etching techniques, directly compatible with high-resolution fluorescence microscopy. Furthermore, we present ultrasonic manipulation in larger up to centimeter-sized devices optimized for fluid mixing and cell lysis. In the present work, two new ultrasonic manipulation platforms have been developed implementing temperature control. These platforms are much improved with increased performance and usability compared to previous platforms. Also, two new ultrasonic platforms utilizing low-frequency ultrasound for solubilization and cell lysis of microliter-volumed and milliliter-volumed samples have been designed and implemented. We have applied ultrasound to synchronize the interaction between large numbers of immune, natural killer cells, and cancer cells to study the cytotoxic response, on a single cell level. A heterogeneity was found among the natural killer cell population, i.e., some cells displayed high cytotoxic response while others were dormant. Furthermore, we have used temperature-controlled ultrasound to form up to 100, in parallel, solid cancer HepG2 tumors in a glass-silicon multi-well microplate. Next, we investigated the immune cells cytotoxic response against the solid tumors. We found a correlation between the number of immune cells compared to the size of the tumor and the cytotoxic outcome, i.e., if the tumor could be defeated. Finally, the effect of high acoustic pressure amplitudes in the MPa-range on cell viability has been studied in a newly developed platform optimized for long-term stable temperature control, independent on the applied ultrasound power. Lastly, we present two applications of ultrasonic fluid mixing and lysis of cells. One platform is optimized for small microliter-sized volumes in plastic disposable chips and another is optimized for large milliliter-sized volumes in plastic test tubes. The latter platform has been implemented for clinical sputum sample solubilization and cell lysis for genomic DNA extraction for subsequent pathogen detection
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| 30. |
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