| 1. |
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| 2. |
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| 3. |
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| 4. |
- Fornell, Anna, et al.
(författare)
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A microfluidic platform for SAXS measurements of liquid samples
- 2022
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Konferensbidrag (refereegranskat)abstract
- Small-angle X-ray scattering (SAXS) is a technique that can measure the size and shape of small particles such as proteins and nanoparticles using X-rays. At MAX IV, we are developing a microfluidic sample delivery platform to measure liquid samples containing proteins under flow using SAXS. One of the main advantages of using microfluidics is that the sample is continuously flowing, thus minimizing the risk of radiation damage as the sample is continuously refreshed. Other advantages include low sample volume and the possibility to study dynamic processes, e.g. mixing. To obtain good SAXS signals, the X-ray properties of the chip material are essential. The microfluidic chip must have low attenuation of X-rays, low background scattering, and high resistance to X-ray-induced damage, and preferably be low cost and easy to fabricate. In this work, we have evaluated the performance of two different polymer microfluidic chips for SAXS measurements.
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| 5. |
- Fornell, Anna, et al.
(författare)
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A Microfluidic Platform for Synchrotron X-ray Studies of Proteins
- 2021
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Konferensbidrag (refereegranskat)abstract
- New tools are needed to allow for complex protein dynamics studies, especially to study proteins in their native states. In the AdaptoCell project a microfluidic platform for academic and industrial users at MAX IV Laboratory is being developed. MAX IV is a Swedish national laboratory providing brilliant synchrotron X-rays for research. Due to the high photon flux, sensitive samples such as proteins are prone to rapid radiation damage; thus, it is advantageous to have the liquid sample underflow to refresh the sample continuously. This, in combination with small volumes, makes microfluidics a highly suitable sample environment for protein studies at MAX IV. The AdaptoCell platform is being integrated at three beamlines:Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and Micromax (serial synchrotron crystallography). Currently, the platform is fully available atBalder, under commissioning at CoSAXS and being developed for MicroMAX.
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| 6. |
- Fornell, Anna, et al.
(författare)
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Acoustic focusing of beads and cells in hydrogel droplets
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 7. |
- Fornell, Anna, et al.
(författare)
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Acoustic focusing of microparticles in two-phase systems - Towards cell enrichment or medium exchange in droplets
- 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. 1026-1028
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Konferensbidrag (refereegranskat)abstract
- We present a method to first laterally position microparticles inside droplets by acoustic forces and then split the droplet into three daughter droplets to achieve a 2+fold enrichment of microparticles inside the center droplet. We show that acoustic forces can be applied to both manipulate polystyrene beads (5 μm) and red blood cells inside droplets. The presented technology opens up for development of droplet operations used for medium exchange and particle concentration in droplet-based cell assays.
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| 8. |
- Fornell, Anna
(författare)
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Acoustic manipulation of cells and microbeads in droplet microfluidics
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Droplet microfluidics has emerged as a promising platform for miniaturisation of biological assays on-chip. In droplet microfluidics small water droplets (nL-pL) surrounded by an immiscible carrier oil are generated at high throughput. In these droplets particles such as cells or microbeads can be encapsulated, and the idea is that each of these droplets can be used as small reaction chambers for biological analyses. However, one key bottleneck for the full implementation of droplet microfluidics in biology has been the lack of a method to position and enrich particles inside droplets. In this thesis I present for the first time a microfluidic system where cells and microbeads encapsulated inside droplets can be manipulated using acoustic standing waves (i.e. acoustophoresis). The developed microfluidic systems were fabricated in silicon and sealed with glass lids. In the experiments, water droplets containing particles were generated, and an acoustic standing wave-field was created between the channel walls by actuating a piezoelectric transducer attached to the chip. In the first study it was shown that at application of the ultrasound at the first harmonic (1.8 MHz), the encapsulated particles were focused to the centre of the droplets i.e. the pressure node. It was shown that both red blood cells and polystyrene microbeads could be aligned in the centre of the droplets. The usefulness of the technology was proved by combining acoustophoresis with a trident-shaped droplet split to allow for particle enrichment. At application of the ultrasound at the first harmonic close to 90% of the particles were positioned in the centre daughter droplets when approximately 2/3 of the original droplet volume was removed. To better understand the physics of the system, in the second study a theoretical model was developed where the acoustic field inside droplets was investigated. In the third study, switching of encapsulated particles between different microfluidic pathways was shown. At application of the ultrasound at the first harmonic the encapsulated particles were directed into pathway 1 (the centre daughter droplets) while at application of the ultrasound at the second harmonic the encapsulated particles were directed into pathway 2 (the side daughter droplets). In the fourth study, two-dimensional acoustophoresis was used to increase the detectability of particles encapsulated inside droplets by pre-aligning the particles before the droplet generation site. In the fifth and last study, it was demonstrated that acoustophoresis can be used to separate two different particle species originally encapsulated in the same droplet into different daughter droplets based on the acoustic properties of the particles.This thesis proves that acoustophoresis is a versatile technology that can find various applications in droplet microfluidics. The combination of droplet microfluidics and acoustophoresis opens up for new possibilities for miniaturisation of biological assays on-chip.
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| 9. |
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| 10. |
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| 11. |
- Fornell, Anna, et al.
(författare)
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Acoustophoretic particle manipulation in droplet microfluidics at higher resonance modes
- 2016
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate focusing of microparticles in the presence of multiple pressure nodes inside aqueous droplets by using bulk acoustic waves. The microfluidic chip s for droplet generation and particle encapsulation (within the droplets) were fabricated using anisotropic wet - etching of a silicon wafer. Subsequently, piezoelectric transducers featuring different thicknesses were glued on the chips to build the final devices. The transducer thicknesses were chosen as to match the acoustic resonances of the embedded micro channel at the fundamental frequency, the first and the second harmonics. The actuation of the devices at the first three resonance modes enabled the positioning of the microparticles in one, two or three bands, in accordance with the presence of pressure nodes within the droplet contained in the microchannel. This acoustic particle manipulation technique opens up for new possibilities to perform biological assays using droplet microfluidic platforms.
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| 12. |
- Fornell, Anna, et al.
(författare)
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AdaptoCell : Microfluidics at MAX IV Laboratory
- 2022
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Ingår i: 25th Swedish Conference on Macromolecular Structure and Function.
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Konferensbidrag (refereegranskat)abstract
- The AdaptoCell project at MAX IV has developed a microfluidic sample delivery platform for academic and industrial users to enable studies of protein samples in solution and in microcrystals underflow. The platform is compatible with various X-ray techniques and has so far been integrated onto two beamlines at MAX IV: the CoSAXS beamline for small angle X-ray scattering studies and the Balder beamline for X-ray absorption spectroscopy studies. Initial implementation of the platform for serial crystallography sample delivery is ongoing and will be integrated onto the BioMAX and MicroMAX beamlines once commissioned. With this platform, we aim to meet the demand from our user community for studying proteins at physiologically relevant temperatures and give the ability to follow dynamical processes in situ as well as decreasing sample volumes and radiation damage.To determine the optimized flow rates and components for mixing etc. using different microfluidic chips, a dedicated off(beam)line test station with a microscope has been established at the Biolab. The Biolab also provides a number of characterization techniques, such as Dynamic Light Scattering, UV-Vis spectrophotometry, for quality control of the samples; as well as an anaerobic chamber for preparation and characterization of metalloproteins. The microfluidic flows are controlled via syringe pumps or a pressure-driven system. Channel design varies, depending on the needs of the experiment, from straight channel, cross-junction to herringbone micromixers etc. On-chip mixing of buffers with different viscosity, pH, ion strength and protein concentrations has been demonstrated successful and will be presented.
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| 13. |
- Fornell, Anna, et al.
(författare)
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AdaptoCell – Microfluidic Platforms at MAX IV Laboratory
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the AdaptoCell project, we are developing microfluidic platforms for X-ray studies of liquid samples. Microfluidics is a suitable technology for samples that are prone to radiation damage, such as proteins. By having the sample underflow, the sample is continuously refreshed, and the risk of radiation damage is reduced. The technology is also suitable for investigating dynamic events such as in situ mixing. The microfluidic platforms are being integrated at three beamlines at MAX IV Laboratory: Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and MicroMAX (serial synchrotron crystallography). Currently, the platforms are available for users at Balder and CoSAXS, which is under development at MicroMAX. In addition, we also provide a microfluidic offline test station where users can test their samples and optimise their devices before the beam time. The main components of the microfluidic setup are the pressure-driven flow controller and the microfluidic chip. We mainly use commercially available polymer microfluidic chips made of COC (cyclic olefin copolymer). COC is used as a chip material as it has high X-ray transmission and high resistance to radiation damage. There are several different chip designs available such as straight channel chips, droplet generator chips and mixing chips. We believe the AdaptoCell platforms will be useful and versatile sample environments for academic and industrial users at MAX IV Laboratory who want to perform experiments with liquid samples under flow.
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| 14. |
- Fornell, Anna, et al.
(författare)
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An acoustofluidic platform for non-contact trapping of cell-laden hydrogel droplets compatible with optical microscopy
- 2019
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Ingår i: Biomicrofluidics. - : AIP Publishing. - 1932-1058. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Production of cell-laden hydrogel droplets as miniaturized niches for 3D cell culture provides a new route for cell-based assays. Such production can be enabled by droplet microfluidics and here we present a droplet trapping system based on bulk acoustic waves for handling hydrogel droplets in a continuous flow format. The droplet trapping system consists of a glass capillary equipped with a small piezoelectric transducer. By applying ultrasound (4 MHz), a localized acoustic standing wave field is generated in the capillary, trapping the droplets in a well-defined cluster above the transducer area. The results show that the droplet cluster can be retained at flow rates of up to 76 mu l/min, corresponding to an average flow speed of 3.2 mm/s. The system allows for important operations such as continuous perfusion and/or addition of chemical reagents to the encapsulated cells with in situ optical access. This feature is demonstrated by performing on-chip staining of the cell nuclei. The key advantages of this trapping method are that it is label-free and gentle and thus well-suited for biological applications. Moreover, the droplets can easily be released on-demand, which facilitates downstream analysis. It is envisioned that the presented droplet trapping system will be a valuable tool for a wide range of multistep assays as well as long-term monitoring of cells encapsulated in gel-based droplets.
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| 15. |
- Fornell, Anna, et al.
(författare)
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An intra-droplet particle switch for droplet microfluidics using bulk acoustic waves
- 2017
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Ingår i: Biomicrofluidics. - : AIP Publishing. - 1932-1058. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- To transfer cell- and bead-assays into droplet-based platforms typically requires the use of complex microfluidic circuits, which calls for methods to switch the direction of the encapsulated particles. We present a microfluidic chip where the combination of acoustic manipulation at two different harmonics and a trident-shaped droplet-splitter enables direction-switching of microbeads and yeast cells in droplet microfluidic circuits. At the first harmonic, the encapsulated particles exit the splitter in the center daughter droplets, while at the second harmonic, the particles exit in the side daughter droplets. This method holds promises for droplet-based assays where particle-positioning needs to be selectively controlled.
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| 16. |
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| 17. |
- 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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| 18. |
- Fornell, Anna, et al.
(författare)
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Binary particle separation in droplet microfluidics using acoustophoresis
- 2018
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 112:6
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Tidskriftsartikel (refereegranskat)abstract
- We show a method for separation of two particle species with different acoustic contrasts originally encapsulated in the same droplet in a continuous two-phase system. This was realized by using bulk acoustic standing waves in a 380 mu m wide silicon-glass microfluidic channel. Polystyrene particles (positive acoustic contrast particles) and in-house synthesized polydimethylsiloxane (PDMS) particles (negative acoustic contrast particles) were encapsulated inside water-in-oil droplets either individually or in a mixture. At acoustic actuation of the system at the fundamental resonance frequency, the polystyrene particles were moved to the center of the droplet (pressure node), while the PDMS particles were moved to the sides of the droplet (pressure anti-nodes). The acoustic particle manipulation step was combined in series with a trifurcation droplet splitter, and as the original droplet passed through the splitter and was divided into three daughter droplets, the polystyrene particles were directed into the center daughter droplet, while the PDMS particles were directed into the two side daughter droplets. The presented method expands the droplet microfluidics tool-box and offers new possibilities to perform binary particle separation in droplet microfluidic systems.
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| 19. |
- Fornell, Anna, et al.
(författare)
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Controlled Lateral Positioning of Microparticles Inside Droplets Using Acoustophoresis
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 87:20, s. 10521-10526
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we utilize bulk acoustic waves to control the position of micropartides inside droplets in two-phase microfluidic systems and demonstrate a method to enrich the micropartides. In droplet microfluidics, different unit operations are combined and integrated on-chip to miniaturize complex biochemical assays. We present a droplet unit operation capable of controlling the position of micropartides during a trident shaped droplet split. An acoustic standing wave field is generated in the microchannel, and the acoustic forces direct the encapsulated micropartides to the center of the droplets. The method is generic, requires no labeling of the micropartides, and is operated in a noncontact fashion. It was possible to achieve 2+-fold enrichment of polystyrene beads (5 mu m in diameter) in the center daughter droplet with an average recovery of 89% of the beads. Red blood cells were also successfully manipulated inside droplets. These results show the possibility to use acoustophoresis in two-phase systems to enrich micropartides and open up the possibility for new droplet-based assays that are not performed today.
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| 20. |
- Fornell, Anna, et al.
(författare)
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Fabrication of Silicon Microfluidic Chips for Acoustic Particle Focusing Using Direct Laser Writing
- 2020
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 21. |
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| 22. |
- Fornell, Anna, et al.
(författare)
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Improved acoustic particle enrichment in droplets by optimising the droplet split design
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Droplet microfluidics has emerged as a valuable platform for miniaturisation of biological experiments on-chip. In droplet microfluidic chips monodisperse droplets containing cells or other bioparticles can be generated at high throughput, and each droplet can be used as an isolated reaction chamber for individual measurements. A general trend in droplet microfluidics is reducing the size of the droplets, but the challenge is maintaining the particles in the droplets after splitting. We have previously reported on an acoustofluidic chip where bulk acoustic waves were used to control particle positioning in a trident-shaped droplet split. However, the reported particle enrichment was modest (3-fold), and the aim of this study is to increase the particle enrichment by optimising the droplet split design. With our new optimised droplet split we show up to 16.7-fold particle enrichment with high particle recovery.
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| 23. |
- Fornell, Anna, et al.
(författare)
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Intra-droplet acoustic particle focusing : simulations and experimental observations
- 2018
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Ingår i: Microfluidics and Nanofluidics. - : Springer Berlin/Heidelberg. - 1613-4982 .- 1613-4990. ; 22:75
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to study resonance conditions for acoustic particle focusing inside droplets in two-phase microfluidic systems. A bulk acoustic wave microfluidic chip was designed and fabricated for focusing microparticles inside aqueous droplets (plugs) surrounded by a continuous oil phase in a 380-μm-wide channel. The quality of the acoustic particle focusing was investigated by considering the influence of the acoustic properties of the continuous phase in relation to the dispersed phase. To simulate the system and study the acoustic radiation force on the particles inside droplets, a simplified 3D model was used. The resonance conditions and focusing quality were studied for two different cases: (1) the dispersed and continuous phases were acoustically mismatched (water droplets in fluorinated oil) and (2) the dispersed and continuous phases were acoustically matched (water droplets in olive oil). Experimentally, we observed poor acoustic particle focusing inside droplets surrounded by fluorinated oil while good focusing was observed in droplets surrounded by olive oil. The experimental results are supported qualitatively by our simulations. These show that the acoustic properties (density and compressibility) of the dispersed and continuous phases must be matched to generate a strong and homogeneous acoustic field inside the droplet that is suitable for high-quality intra-droplet acoustic particle focusing.
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| 24. |
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| 25. |
- Fornell, Anna, et al.
(författare)
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Optimisation of the droplet split design for high acoustic particle enrichment in droplet microfluidics
- 2020
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 226
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Tidskriftsartikel (refereegranskat)abstract
- We have characterised three droplet split designs for acoustic particle enrichment in water-in-oil droplets. The microfluidic channel design included a droplet generation junction, acoustic focusing channel and a trident-shaped droplet split. The microfluidic channels were dry-etched in silicon and sealed with glass lids by anodic bonding. To each microfluidic chip a piezoelectric transducer was glued, and at actuation of the transducer at the fundamental resonance frequency of the acoustic focusing channel (1.91–1.93 MHz), a half wavelength standing wave field was created between the channel walls. The acoustic force focused the encapsulated particles (3.2 μm, 4.8 μm and 9.9 μm diameter polystyrene microbeads) to the centre-line of the droplets, and when the droplets reached the droplet split the particles were directed into the centre daughter droplets. The results show that the design of the droplet split and the flow ratio between the centre and side outlet channels are the main factors that affect the particle enrichment and particle recovery in the centre daughter droplets. The highest particle enrichment was achieved in the droplet split design having the smallest centre channel (38 μm wide). Using this microfluidic chip design, we demonstrate up to 16.7-fold enrichment of 9.9 μm diameter polystyrene microbeads in the centre daughter droplets. This is almost three times higher particle enrichment than what has previously been presented using other intra-droplet particle enrichment techniques. Moreover, the acoustic technique is label-free and biocompatible.
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| 26. |
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| 27. |
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| 28. |
- Fornell, Anna, et al.
(författare)
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Trapping of Cell-Laden Hyaluronic Acid-Acrylamide Hydrogel Droplets using Bulk Acoustic Waves
- 2019
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Ingår i: 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII). - : IEEE. - 9781538681046 - 9781728120072 ; , s. 2352-2355
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Konferensbidrag (refereegranskat)abstract
- In this paper an acoustofluidic system to trap hydrogel droplets is shown. The presented trapping method is label-free, biocompatible and operated in non-contact mode. The results show that the droplets can be trapped at flow rates up to 76 mu L/min which corresponds to an average flow speed of 3.2 mm/s. Moreover, it is shown that the droplets can be trapped for several hours, thus allowing for studies of the encapsulated cells over time. An application of the system is shown by performing on-chip cell nuclei staining.
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| 29. |
- Gilbert, Jennifer, et al.
(författare)
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Evolution of the structure of lipid nanoparticles for nucleic acid delivery : From in situ studies of formulation to colloidal stability
- 2024
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797. ; 660, s. 66-76
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Tidskriftsartikel (refereegranskat)abstract
- The development of lipid nanoparticle (LNP) based therapeutics for delivery of RNA has triggered the advance of new strategies for formulation, such as high throughput microfluidics for precise mixing of components into well-defined particles. In this study, we have characterised the structure of LNPs throughout the formulation process using in situ small angle x-ray scattering in the microfluidic chip, then by sampling in the subsequent dialysis process. The final formulation was investigated with small angle x-ray (SAXS) and neutron (SANS) scattering, dynamic light scattering (DLS) and cryo-TEM. The effect on structure was investigated for LNPs with a benchmark lipid composition and containing different cargos: calf thymus DNA (DNA) and two model mRNAs, polyadenylic acid (polyA) and polyuridylic acid (polyU). The LNP structure evolved during mixing in the microfluidic channel, however was only fully developed during the dialysis. The colloidal stability of the final formulation was affected by the type of incorporated nucleic acids (NAs) and decreased with the degree of base-pairing, as polyU induced extensive particle aggregation. The main NA LNP peak in the SAXS data for the final formulation were similar, with the repeat distance increasing from polyU
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| 30. |
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| 31. |
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| 32. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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A continuous on-chip droplet washing platform with high bead recovery by acoustofluidics
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Acoustofluidics is a promising technology for manipulation of fluids and particles in microchannels, and the technology has the ability to sort beads and cells in continuous flow with very high efficiency. Recently acoustofluidics has also been applied in segmental flow for positioning beads inside droplets. Compared with single-phase systems, droplet microfluidics has the advantages of faster reactions, lower cross-contamination and higher throughput. Moreover, the small size of the droplets makes them ideal as cultivation and reaction vials for single cell analysis. However, as the droplets are so small one challenge is to wash the droplets before image analysis. P. Mary et al. developed a microfluidic platform for droplet wash, whichis based on electrocoalescence and droplet break-ups with equal volume. The background noise was decreased significantly, however the recovery of the encapsulated cells was low. Alternative solutions have been presented by H. Lee et al. and S.R. Doonan et al. but as the bead recovery is controlled via magnetophoresis, the technology is only applicable to magnetic samples. Here we present a droplet microfluidic platform that enables background dilution with high bead recovery in a label-free manner using acoustophoresis.
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| 33. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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A droplet acoustofluidic platform for time-controlled microbead-based reactions
- 2021
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Ingår i: Biomicrofluidics. - : American Institute of Physics (AIP). - 1932-1058. ; 15:3
-
Tidskriftsartikel (refereegranskat)abstract
- Droplet microfluidics is a powerful method used to characterize chemical reactions at high throughput. Often detection is performed via in-line optical readout, which puts high demands on the detection system or makes detection of low concentration substrates challenging. Here, we have developed a droplet acoustofluidic chip for time-controlled reactions that can be combined with off-line optical readout. The principle of the platform is demonstrated by the enzymatic conversion of fluorescein diphosphate to fluorescein by alkaline phosphatase. The novelty of this work is that the time of the enzymatic reaction is controlled by physically removing the enzymes from the droplets instead of using chemical inhibitors. This is advantageous as inhibitors could potentially interact with the readout. Droplets containing substrate were generated on the chip, and enzyme-coupled microbeads were added into the droplets via pico-injection. The reaction starts as soon as the enzyme/bead complexes are added, and the reaction is stopped when the microbeads are removed from the droplets at a channel bifurcation. The encapsulated microbeads were focused in the droplets by acoustophoresis during the split, leaving the product in the side daughter droplet to be collected for the analysis (without beads). The time of the reaction was controlled by using different outlets, positioned at different lengths from the pico-injector. The enzymatic conversion could be measured with fluorescence readout in a separate PDMS based assay chip. We show the ability to perform time-controlled enzymatic assays in droplet microfluidics coupled to an off-line optical readout, without the need of enzyme inhibitors.
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| 34. |
- Liu, Zhenhua, 1992-
(författare)
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Droplet Acoustofluidics for Biochemical Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Droplet microfluidics is a promising platform for biochemical applications where compartmentalized droplets serve as individual vials. Droplets are formed by using two immiscible phases, the continuous phase and the dispersed phase, making up the droplets. Droplets are interesting because they can provide fast, parallel reactions with low reagent consumption. Microscale particles, such as cells, can be encapsulated in the droplets and chemical reagents can be added via a pico-injector. However, removal of droplet background signal is hard to achieved by conventional methods, especially if you do not want to risk losing the encapsulated cells. In this thesis, I present a droplet microfluidic system that can achieve this, via droplet-internal particle manipulation using acoustophoresis.This droplet microfluidic system contains pico-injection and droplet split with acoustophoresis. The pico-injection is used to add fresh solution into the droplets and the droplet split with acoustophoresis is used to remove the droplet supernatant. With the combination of the pico-injector and the droplet split, the background signal of the droplets can be reduced and the cell medium in the droplets can be exchanged. This droplet microfluidic system can also be used to control timing of enzyme reactions by initiating the reaction by adding enzyme-coupled beads via the pico-injector and taking a sample from the droplets at specific time points via side channels. In this work, I have also investigated how the design of the droplet split could be optimized to obtain high particle recovery and enrichment. Finally, acoustic properties of a selection of oils that can used as the continuous phase were mapped to optimize the droplet system for acoustophoresis.This thesis explores the biochemical applications performed by the droplet acoustofluidics, in-droplet time-controlled enzyme reaction and medium exchange for in-droplet cell culture. Furthermore, the droplet acoustofluidics has the potential to study the reaction kinetics by other enzymes and achieve long-term in-droplet cell culture.
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| 35. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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Droplet Dilution Unit Operation Including Bead Washing Using Integrated Acoustophoresis
- 2019
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Ingår i: 2019 20TH INTERNATIONAL CONFERENCE ON SOLID-STATE SENSORS, ACTUATORS AND MICROSYSTEMS & EUROSENSORS XXXIII (TRANSDUCERS & EUROSENSORS XXXIII). - : IEEE. ; , s. 2333-2336
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Konferensbidrag (refereegranskat)abstract
- This paper presents a microfluidic platform on-chip droplet dilution where the bead recovery also can be controlled. The droplets containing 10 mu m polystyrene beads can be diluted with high bead recovery. This platform involves 5 steps for on-chip dilution of the droplets: droplet generation, bead focusing, droplet splitting, pica-injection and serpentine mixing. Background signal in the droplets is significantly reduced with maintained bead recovery by this on-chip dilution method. The technology is applicable to many types of samples and does not require any labelling of the bioparticles.
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| 36. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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Enabling off-chip analysis for in-droplet enzyme reactions using acoustophoresis
- 2021
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Konferensbidrag (refereegranskat)abstract
- Acoustophoresis is a commonly used technique to manipulate microbeads suspended in single-phase fluids [1]. Fornell et al. demonstrated that acoustophoresis can also be used to manipulate microbeads in droplets when the acoustic properties of the continuous phase match with the acoustic properties of the dispersed phase [2]. Water-in-oil droplets can be considered to be ideal vials for liquid mixing and reactions, as they allow for high throughput, low cross-contamination and low reagent consumption. Droplet microfluidics has previously been applied to study enzyme reactions [3,4]. However, these approaches are limited by on-chip detection and analysis since the enzyme is mixed with the product of the reaction inside the droplets. Here, we present an acoustofluidic chip where we can start the enzymatic reaction by injecting enzyme-coupled microbeads into the droplets containing the substrate by pico-injection and then stop the enzymatic reaction by removing the enzyme-coupled microbeads using acoustophoresis [5]. The analysis can then be performed off-chip, which allows for longer exposure times compared to performing the analysis in-line.
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| 37. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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Long-term droplet cell culture enabled by droplet acoustofluidics
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Droplet microfluidics can be used to encapsulate cells for biochemical applications, such as single-cell analysis and drug screening. However, the concentration of nutrients and growth factors decreases over time, while the concentration of catabolic byproducts increases, that make droplet hard for long-term cell culture. Here, the cells encapsulated in droplets continued to divide in the first 8 hours and then stopped to grow. We developed a droplet acoustofluidic chip that can exchange cell medium in droplets by the combination of the pico-injection and the droplet split with acoustophoresis. After running droplets through this chip, cell medium in droplets got exchanged and the cells in droplets started to grow again. By this way, long-term droplet cell culture can be achieved.
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| 38. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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On-chip background dilution in droplets with high particle recovery using acoustophoresis
- 2019
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Ingår i: Biomicrofluidics. - : AIP Publishing. - 1932-1058. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery. The system comprises droplet generation, acoustic focusing, droplet splitting, picoinjection, and serpentine mixing on the same chip. The capacities of the picoinjection and the droplet split to dilute the background fluorescent signal in the droplets have been characterized. The sample recovery at different droplet split ratios has also been characterized. The results show a maximum of 4.3-fold background dilution with 87.7% particle recovery. We also demonstrated that the system can be used to dilute background fluorescent signal in droplets containing either polystyrene particles or endothelial cells.
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| 39. |
- Liu, Zhenhua, 1992-, et al.
(författare)
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Time-controlled Microbead-based Reactions in Droplets using Acoustophoresis
- 2021
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Ingår i: MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419031 ; , s. 893-894
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Konferensbidrag (refereegranskat)abstract
- Droplet microfluidics is a powerful method to characterize chemical reactions at high throughput. Often detection is performed via in-line optical readout, which puts high demands on the detection system and makes detection of low concentration substrates challenging. Here, we have developed a droplet acoustofluidic chip for time-controlled microbead-based reactions that is combined with off-line optical readout.
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| 40. |
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| 41. |
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| 42. |
- 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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| 43. |
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| 44. |
- Pohlit, Hannah, et al.
(författare)
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ACOUSTOFLUIDIC METHOD TO ALIGN POLYSTYRENE BEADS AND CELLS IN HYDROGEL DROPLETS
- 2021
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Ingår i: MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419031 ; , s. 887-888
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Konferensbidrag (refereegranskat)abstract
- We present a microfluidic system to control the position of particles (polystyrene beads or astrocyte cells) in hydrogel droplets using bulk acoustic standing waves. Droplets comprising hydrogel precursor solution, photoinitiator and (bio-)particles were generated and acoustic forces focused the beads to the droplet center line. Droplets were cross-linked by exposure to UV-light. With the acoustics applied, 89 ± 19% of the particles were positioned in the center of the hydrogel droplet. As proof-of-principle for biological applications, astrocytes were focused in hydrogel droplets. The viability of the cells after 7 days was unaffected by the acoustic focusing (72 ± 22%).
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| 45. |
- Pohlit, Hannah, et al.
(författare)
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Evaluation of biocompatibility of acousticfocusing of cells in hydrogel droplets
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionDroplet microfluidics has become a powerful tool to generate miniaturized compartments suitable for biologicalexperiments.[1] For example, hydrogel droplets are a suitable platform to study 3D cell culture.[2] For thisapplication, it can be advantageous to prepare hydrogel constructs with an ordered cell architecture. Here, wepresent an acoustic method to align cells in hydrogel droplets and demonstrate its biocompatibility.Experimental procedure and ResultsTo position the cells in a line at the center of the droplets, we use acoustophoresis. The microfluidic chip wasfabricated using deep reactive ion etching of a Si wafer to form the channels and anodic bonding of a glass waferto seal the chip. A piezoelectric transducer was glued to the chip and actuated to generate bulk acoustic waves inthe channel. The channel dimensions were 380 μm x 100 μm (width x height), which corresponds to halfwavelength lateral resonance at 2 MHz. Droplets consisting of hydrogel precursor solution (3 wt% 4-arm-PEG(10000)-acrylate, 1 wt% gelatin methacrylate and 0.1 wt% photoinitiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP)) were formed. The cells, 5 × 106 astrocytes/mL encapsulated in the hydrogeldroplets, were focused at the center of the droplets (pressure nodal line) by the primary acoustic radiation force,Fig 1a). By exposing the cell-laden droplets to a short UV dose, the hydrogel precursor solution was cross-linkedand the cells were “frozen” in their position. Viability of acoustically focused cells and non-focused cells (noacoustics applied) encapsulated in the cross-linked droplets were evaluated by live/dead staining, demonstratingthat acoustic focusing and on-chip cross-linking with UV is a gentle process, see Fig. 1b).[3]Figure 1: a) The experimental procedure. b) Focused polystyrene beads in a cross-linked hydrogel droplet. c) Focusedastrocytes in a cross-linked hydrogel droplet. d) The viability of astrocytes in hydrogel droplets after 1, 3 and 7 days of culture.In blue, acoustically focused cells are shown, whereas in grey, the control group (astrocytes encapsulated in hydrogel dropletswithout acoustic focusing) is shown after 7 days of culture.ConclusionA microfluidic chip with an integrated piezoelectric transducer can be used to generate hydrogel dropletswhere the encapsulated cells are focused to the center line of the droplets· Acoustic focusing of cells do not decrease cell viability· The generated hydrogel droplets could be suitable cell culture scaffolds for advanced biological studies.
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| 46. |
- Shi, Qian, et al.
(författare)
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Mapping the acoustic properties of two-phase systems for use in droplet acoustofluidics
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The emergence of droplet microfluidics as a powerful tool for on-chip biological assays has prompted the development of a variety of intra-droplet particle manipulation techniques, such as droplet acoustofluidics. Previous study has shown that the acoustic properties between the continuous and dispersed phase must match for high-quality intra-droplet particle focusing. As a follow up, this study investigates the acoustic properties, i.e., speed of sound and density, of a selection of non-polar fluids that can be used as the continuous phase in droplet microfluidic systems. Our experimental results show that within our collection, linseed oil is the non-polar phase that most closely matches the acoustic properties of water and the fluorinated oil HFE-7500 is the one that least matches the acoustic properties compared to water. We believe this collection of data will serve the community by providing results that aid in the selection of continuous phase in future droplet acoustofluidic studies and data for performing acoustofluidic simulations.
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| 47. |
- Tenje, Maria, et al.
(författare)
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Particle Manipulation Methods in Droplet Microfluidics
- 2018
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:3, s. 1434-1443
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Tidskriftsartikel (refereegranskat)abstract
- This Feature article describes the different particle manipulation techniques available in the droplet microfluidics tool-box to handle particles encapsulated inside droplets and to manipulate whole droplets. We address the advantages and disadvantages of the different techniques to guide new users.
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