| 1. |
- Akbari, Elham, et al.
(författare)
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SEPARATION OF CLUSTERS OF GROUP A STREPTOCOCCI USING DETERMINISTIC LATERAL DISPLACEMENT
- 2021
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Ingår i: MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419031 ; , s. 1201-1202
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Konferensbidrag (refereegranskat)abstract
- Differences in morphologies of bacteria and bacteria clusters are known to influence their pathogenicity. However, it is difficult to separate cells and cell clusters based on morphology using standard cell biological methods, making studies of the underlying mechanisms difficult. Here we report a simple label-free method for the continuous separation of clusters of group A streptococci, based on cluster size and morphology, using Deterministic Lateral Displacement (DLD). In general, this opens up for the generation of cell populations with heterogenicity in cluster size and physical properties.
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| 2. |
- Akbari, Elham, et al.
(författare)
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SEPARATION OF SINGLETS AND CLUSTERS OF GROUP A STREPTOCOCCI USING DETERMINISTIC LATERAL DISPLACEMENT AND FILTER SONICATION
- 2022
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Ingår i: MicroTAS 2022 - 26th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419048 ; , s. 306-307
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Konferensbidrag (refereegranskat)abstract
- Differences in morphologies of bacteria and bacteria clusters are thought to contribute to their virulence and colonization. However, the conventional standard cell biological methods cannot separate bacteria and bacteria clusters based on their morphologies and sizes, making studies of the underlying mechanisms difficult. Here we report a simple label-free method for the continuous separation of singlets and clusters, of group A streptococci, based on their size and morphology, using Deterministic Lateral Displacement and filter-sonication. In general, this opens up for the generation of cell populations with heterogenicity in cluster size and physical properties.
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| 3. |
- Al-Fandi, M, et al.
(författare)
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Nano-engineered living bacterial motors for active microfluidic mixing.
- 2010
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Ingår i: IET Nanobiotechnology. - : Institution of Engineering and Technology (IET). - 1751-875X .- 1751-8741. ; 4:3, s. 61-71
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Tidskriftsartikel (refereegranskat)abstract
- Active micromixers with rotating elements are attractive microfluidic actuators in many applications because of their mixing ability at a short distance. However, miniaturising the impeller design poses technical challenges including the fabrication and driving means. As a possible solution inspired by macro magnetic bar-stirrers, this study proposes the use of tethered, rotating bacteria as mixing elements. A tethered cell is a genetically engineered, harmless Escherichia coli (E. coli) attached to a surface by a single, shortened flagellum. The tethered flagellum acts as a pivot around which the entire cell body smoothly rotates. Videomicroscopy, image analysis and computational fluid dynamics (CFD) are utilised to demonstrate a proof-of-concept for the micro mixing process. Flow visualisation experiments show that a approximately 3 [micro sign]m long tethered E. coli rotating at approximately 240 rpm can circulate a 1 [micro sign]m polystyrene bead in the adjacent area at an average speed of nearly 4 [micro sign]m/s. The Peclet (Pe(b)) number for the stirred bead is evaluated to approximately 4. CFD simulations show that the rotary motion of a tethered E. coli rotating at 240 rpm can generate fluid velocities, up to 37 [micro sign]m/s bordering the cell envelop. Based on these simulations, the Strouhal number (St) is calculated to about 2. This hybrid bio-inorganic micromxer could be used as a local, disposable mixer.
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| 4. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Habitat complexity affects microbial growth in fractal maze
- 2023
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Ingår i: Current biology : CB. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 33:8, s. 4-1458
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Tidskriftsartikel (refereegranskat)abstract
- The great variety of earth's microorganisms and their functions are attributed to the heterogeneity of their habitats, but our understanding of the impact of this heterogeneity on microbes is limited at the microscale. In this study, we tested how a gradient of spatial habitat complexity in the form of fractal mazes influenced the growth, substrate degradation, and interactions of the bacterial strain Pseudomonas putida and the fungal strain Coprinopsis cinerea. These strains responded in opposite ways: complex habitats strongly reduced fungal growth but, in contrast, increased the abundance of bacteria. Fungal hyphae did not reach far into the mazes and forced bacteria to grow in deeper regions. Bacterial substrate degradation strongly increased with habitat complexity, even more than bacterial biomass, up to an optimal depth, while the most remote parts of the mazes showed both decreased biomass and substrate degradation. These results suggest an increase in enzymatic activity in confined spaces, where areas may experience enhanced microbial activity and resource use efficiency. Very remote spaces showing a slower turnover of substrates illustrate a mechanism which may contribute to the long-term storage of organic matter in soils. We demonstrate here that the sole effect of spatial microstructures affects microbial growth and substrate degradation, leading to differences in local microscale spatial availability. These differences might add up to considerable changes in nutrient cycling at the macroscale, such as contributing to soil organic carbon storage.
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| 5. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Habitat geometry in artificial microstructure affects bacterial and fungal growth, interactions, and substrate degradation
- 2021
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Microhabitat conditions determine the magnitude and speed of microbial processes but have been challenging to investigate. In this study we used microfluidic devices to determine the effect of the spatial distortion of a pore space on fungal and bacterial growth, interactions, and substrate degradation. The devices contained channels differing in bending angles and order. Sharper angles reduced fungal and bacterial biomass, especially when angles were repeated in the same direction. Substrate degradation was only decreased by sharper angles when fungi and bacteria were grown together. Investigation at the cellular scale suggests that this was caused by fungal habitat modification, since hyphae branched in sharp and repeated turns, blocking the dispersal of bacteria and the substrate. Our results demonstrate how the geometry of microstructures can influence microbial activity. This can be transferable to soil pore spaces, where spatial occlusion and microbial feedback on microstructures is thought to explain organic matter stabilization.
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| 6. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Quantification of growth and nutrient consumption of bacterial and fungal cultures in microfluidic microhabitat models
- 2024
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Ingår i: STAR Protocols. - 2666-1667. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding microbes in nature requires consideration of their microenvironment. Here, we present a protocol for quantifying biomass and nutrient degradation of bacterial and fungal cultures (Pseudomonas putida and Coprinopsis cinerea, respectively) in microfluidics. We describe steps for mask design and fabrication, master printing, polydimethylsiloxane chip fabrication, and chip inoculation and imaging using fluorescence microscopy. We include procedures for image analysis, plotting, and statistics. For complete details on the use and execution of this protocol, please refer to Arellano-Caicedo et al. (2023).1
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| 7. |
- Barrett, Michael P., et al.
(författare)
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Microfluidics-based approaches to the isolation of African trypanosomes
- 2017
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Ingår i: Pathogens. - : MDPI AG. - 2076-0817. ; 6:4
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Forskningsöversikt (refereegranskat)abstract
- African trypanosomes are responsible for significant levels of disease in both humans and animals. The protozoan parasites are free-living flagellates, usually transmitted by arthropod vectors, including the tsetse fly. In the mammalian host they live in the bloodstream and, in the case of human-infectious species, later invade the central nervous system. Diagnosis of the disease requires the positive identification of parasites in the bloodstream. This can be particularly challenging where parasite numbers are low, as is often the case in peripheral blood. Enriching parasites from body fluids is an important part of the diagnostic pathway. As more is learned about the physicochemical properties of trypanosomes, this information can be exploited through use of different microfluidic-based approaches to isolate the parasites from blood or other fluids. Here, we discuss recent advances in the use of microfluidics to separate trypanosomes from blood and to isolate single trypanosomes for analyses including drug screening.
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| 8. |
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| 9. |
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| 10. |
- Beech, Jason
(författare)
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Microfluidics Separation and Analysis of Biological Particles
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last decade, powerful communication and information technology in the form of the mobile phone has been put into the hands of more than 50% of the global population. In stark contrast, a lack of access to medical diagnostic technology with which to diagnose both communicable and non-communicable diseases will mean that many of these people will die of easily treatable conditions. Small, portable, effective and affordable devices able to give relevant information about the health of an individual, even in resource poor environments, could potentially help to change this. And the developing world is not the only resource poor environment; areas struck by natural disaster or by outbreaks of infectious disease or on the battlefield or even at the frontiers of exploration we find environments in which a mobile phone-sized laboratory would have a profound impact, not only on medical, but environmental diagnostics. There are also less dramatic examples. Compared to a well-equipped hospital most environments are resource poor, including the home. Blood sugar measuring devices for example put important information immediately into the hands of the diabetes sufferer in their own home, allowing them to make informed, life-saving decisions about food intake and medication without recourse to medical doctors. These diagnostic devices will be based on technologies that go under the collective names of micro-total-analysis systems, µTAS, or Lab-on-a-Chip. One of the uniting, integral features of all these technologies is the need to manipulate small volumes of fluids, often containing cells or other particles, from which the diagnostic information is to be wrung. The manipulation of such small volumes of fluids is known as microfluidics. This doctoral thesis is concerned with particle separation science. More specifically it is concerned with the development of tools for the separation of biologically relevant particles, an important step in almost any analysis, using techniques that have been made possible through the advent of microfluidics. A technique based on the flow of fluid through arrays of micrometre-sized obstacles, Deterministic Lateral Displacement (DLD), is promising because of its exceptional resolution, its suitability for biological separations, the wide range of sizes across which it works and not least because of the promise it holds as a candidate for integration within a lab-on-a-chip. The first devices utilizing the principle were limited to use in the separation of particles by size only. However, there are many physical properties other than size holding a wealth of information about particles, for example cancer and infection with malaria or HIV have been shown to change the deformability of cells and so measuring deformability could provide a means of diagnosing these conditions. The central tenet of this work is that DLD can be used to separate particles by highly relevant physical properties other than size, for example shape, deformability or electrical properties and that devices that can do this in a cheap and simple way will constitute powerful particle separation tools, useful for diagnostic applications and well suited for integration in a Lab-on-a-Chip. The aim of this thesis is to present four research papers, documenting the development of new methods that improve the existing DLD technique. Paper I describes how the elastomeric properties of polydimethylsiloxane can be utilized to achieve tuneable separation in DLD devices, making it easier to take advantage of the high resolution inherent in the method. Paper II presents the use of dielectrophoresis to achieve tuneability, improve dynamic range and open up for the separation of particles with regard to factors other than size. Paper III describes how control of particle orientation can be used to separate particles based on their shape and how this can be used to separate blood-borne parasites from blood. Finally Paper IV deals with the size, shape and deformability of cells and how DLD devices can be used, both to measure these properties, and to perform separations based on them. The hope is that these methods might ultimately play a small part in helping diagnostics technology to become as ubiquitous as information technology has become in the last ten years and that this will have a profound impact on global health.
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| 11. |
- Beech, Jason P., et al.
(författare)
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Active Posts in Deterministic Lateral Displacement Devices
- 2019
-
Ingår i: Advanced Materials Technologies. - : Wiley. - 2365-709X. ; 4:9
-
Tidskriftsartikel (refereegranskat)abstract
- Using electrically connected metal-coated posts in a deterministic lateral displacement (DLD) device and applying electric fields, electrokinetics is used to tune separations, significantly decrease the critical size for separation, and increase the dynamic range with switching times on the order of seconds. The strength of DLD stems from its binary behavior. To first approximation, particles move in one out of two trajectories based on their effective size. For particles that are close to the threshold size, a small external force is sufficient to nudge the particles from one trajectory to another. The devices consist of arrays of cylindrical metal-coated SU-8 posts connected by an underlying metal layer. This allows the application of voltages at the post surfaces and the generation of electric field gradients between neighboring posts, causing polarizable particles to experience a dielectrophoretic (DEP) force. This force, which depends on the volume and polarizability of the particle, can be made sufficient to push particles from one trajectory into another. In this way, the critical size in a device, normally fixed by the geometry, can be tuned. What's more, adding DEP in this way allows for the simultaneous creation of multiple size fractions.
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| 12. |
- Beech, Jason P., et al.
(författare)
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Capillary driven separation on patterned surfaces
- 2009
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Ingår i: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 785-787
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Konferensbidrag (refereegranskat)abstract
- Deterministic lateral displacement (DLD) is a powerful bimodal separation scheme [1] based on fluid flow through regular obstacle arrays that in its basic embodiment sends suspended particles in two different directions as a function of size. We show that without the need to seal devices and without the need for fluidic connections or pumps, particle separation can be achieved by the passive flow of a sample over a patterned surface. Risk of clogging is minimized by the movement of large particles above the obstacle array. Suitable application areas include blood fractionation and analysis of drinking water. 0
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| 13. |
- Beech, Jason P., et al.
(författare)
-
Cell morphology and deformability in deterministic lateral displacement devices
- 2011
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Ingår i: 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2011, MicroTAS 2011. - 9781618395955 ; 2, s. 1355-1357
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Konferensbidrag (refereegranskat)abstract
- Deterministic Lateral Displacement (DLD) devices have been used to separate particles based on size [1] and shape [2]. Here we show how DLD devices can also be used to separate particles based on their ability to deform under shear forces. Varying experimental conditions allows us to vary the relative contributions of size, morphology and deformability. The ability to distinguish between cells based on deformability with high resolution and throughput, in cheap and simple devices, could find highly interesting and relevant applications, for example in the detection of circulating tumor cells or malaria-infected blood cells.
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| 14. |
- Beech, Jason P., et al.
(författare)
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Electrokinetic wall effect mechanisms and applications
- 2020
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Ingår i: MicroTAS 2020 - 24th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419017 ; , s. 42-43
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Konferensbidrag (refereegranskat)abstract
- Under the application of longitudinal electric fields in microchannels, microparticles experience lift forces that push them away from the channel walls and affect their trajectories. At high frequencies (>100KHz) the dielectrophoretic forces dominate and are well understood but at lower frequencies there is little agreement as to the exact nature of the forces, how they are generated and how they vary due to the many different experimental conditions that are used in microfluidics devices. Here we present an experimental study of these mechanisms.
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| 15. |
- Beech, Jason P., et al.
(författare)
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Gravitationally driven deterministic lateral displacement devices
- 2009
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Ingår i: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 779-781
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Konferensbidrag (refereegranskat)abstract
- Deterministic lateral displacement (DLD) is a powerful bimodal separation scheme [1] based on regular obstacle arrays that in its basic embodiment sends particles in two different directions as a function of size. We add functionality to the technique by including gravitational forces, as a perturbation to particles transported by fluid flow, and as a way of transporting the particles through a stationary fluid.
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| 16. |
- Beech, Jason P., et al.
(författare)
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Morphology-based sorting-blood cells and parasites
- 2010
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Ingår i: 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2010, MicroTAS 2010. - 9781618390622 ; 2, s. 1343-1345
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Konferensbidrag (refereegranskat)abstract
- Morphology represents a hitherto unexploited source of specificity in microfluidic particle separation and may serve as the basis for label-free particle fractionation. There is a wealth of morphological changes in blood cells due to a wide range of clinical conditions, diseases, medication and other factors. Also, blood-borne parasites differ in morphology from blood cells. We present the use of Deterministic Lateral Displacement to create a chip-based, label-free diagnostic tool, capable of harvesting some of the wealth of information locked away in red blood cell morphology. We also use the device to separate the parasites that cause sleeping sickness from blood.
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| 17. |
- Beech, Jason P., et al.
(författare)
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Sample preparation for single-cell whole chromosome analysis
- 2012
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Ingår i: Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012. - 9780979806452 ; , s. 998-999
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Konferensbidrag (refereegranskat)abstract
- In this work we present an integrated system for whole chromosome analysis of single bacterium. Using whole genome barcoding techniques, which offer direct and rapid microscopic visualization of the entire genome in one field-of-view, we aim to rapidly identify individual bacterium. We are developing our device to achieve the crucial, and difficult process of isolating a bacterium, removing the DNA in one piece and transferring it to a nano-channel for visualisation. In order to achieve control over the bacteria we encapsulate them in agarose, using flow focusing. The encapsulated bacteria can then be transported in microchannels to proximity with the nanochannels and then chemically lysis can be performed. Following lysis the intact genome can be extracted and transferred to the meandering nanochannel for analysis. We believe this device holds the potential to significantly decrease analysis times for single cell, whole genome analysis with the potential of opening up for automated, high-throughput genome analysis in microfluidic systems.
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| 18. |
- Beech, Jason P., et al.
(författare)
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Separation of pathogenic bacteria by chain length
- 2018
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 1000, s. 223-231
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Tidskriftsartikel (refereegranskat)abstract
- Using Deterministic Lateral Displacement devices optimized for sensitivity to particle length, we separate subpopulations of bacteria depending on known properties that affect their capability to cause disease (virulence). For the human bacterial pathogen Streptococcus pneumoniae, bacterial chain length and the presence of a capsule are known virulence factors contributing to its ability to cause severe disease. Separation of cultured pneumococci into subpopulations based on morphological type (single cocci, diplococci and chains) will enable more detailed studies of the role they play in virulence. Moreover, we present separation of mixed populations of almost genetically identical encapsulated and non-encapsulated pneumococcal strains in our device.
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| 19. |
- Beech, Jason P., et al.
(författare)
-
Shape-based particle sorting - A new paradigm in microfluidics
- 2009
-
Ingår i: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9780979806421 ; , s. 800-802
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Konferensbidrag (refereegranskat)abstract
- Conventional fractionation techniques fail to fully benefit from the variety in morphology and shape that is found among biological particles. Although light scattering in conventional FACS gives some information on the size and morphology of a particle, it is generally not capable of giving a definite number on specified dimensions of a small object. We demonstrate an approach where we select which dimension of a particular object is used to determine its trajectory through an obstacle course and thereby sort not merely with respect to hydrodynamic radius but rather with respect to e.g. thickness, length or width.
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| 20. |
- Beech, Jason P., et al.
(författare)
-
Sorting bacteria by chain length - A factor of virulence?
- 2016
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Ingår i: 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016. - 9780979806490 ; , s. 250-251
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Konferensbidrag (refereegranskat)abstract
- Using Deterministic Lateral Displacement (DLD), we are able to separate bacteria by their size and their chain length. This separation enables the study of these properties as factors of virulence.
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| 21. |
- Beech, Jason P., et al.
(författare)
-
The separation and identification of parasite eggs from horse feces
- 2019
-
Ingår i: 23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2019. - 9781733419000 ; , s. 602-603
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Konferensbidrag (refereegranskat)abstract
- Freely grazing horses are at risk of infection by parasites such as Parascaris equorum (roundworm), Strongylus spp. (large bloodworms), Cyathostomes (small bloodworms), and Anoplochephala perfoliata (tapeworms). Mixed infections are common and diagnosis is based on demonstrations of eggs in feces followed by identification of larvae after fecal culture. Drug resistance is a growing problem, not least because treatments tend to be cheaper than diagnosis and “just in case” treatments common. There is a need for improved methods that are easy to use, rapid and cheap. Furthermore, a successful approach may find use with other livestock such as ruminants and pigs.
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| 22. |
- Beech, Jason P., et al.
(författare)
-
The separation of nano-sized particles in micro-scaled post arrays
- 2019
-
Ingår i: 23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2019. - 9781733419000 ; , s. 10-11
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Konferensbidrag (refereegranskat)abstract
- The precise separation of nanoscale particles has proven challenging due to diffusion and the need to use nanoscale devices. We show the separation of particles in the 100 nm size range in Deterministic Lateral Displacement (DLD) devices with feature sizes in the 10 µm size range. We achieve this using Dielectrophoretic (DEP) forces, generated between the metal coated posts that act as active electrodes. This opens up for the separation of submicron particles based not only on size but also on electric and dielectric properties.
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| 23. |
- Beech, Jason P., et al.
(författare)
-
Throughput through thin-film fluidics
- 2008
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Ingår i: ; , s. 1492-1494
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Konferensbidrag (refereegranskat)abstract
- We demonstrate fluidics realized in thin film plastic foils patterned using roll-toroll nanoimprinting lithography (rrNIL). Realizing fluidics devices in thin plastic foils opens up for parallel operation in stacked devices. It also provides a convenient format for storage and distribution of the devices.
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| 24. |
- Beech, Jason P., et al.
(författare)
-
Tipping the balance with dielectrophoretic forces - An electric deterministic lateral displacement device
- 2008
-
Ingår i: ; , s. 95-97
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Konferensbidrag (refereegranskat)abstract
- We present experimental results and simulations on a simple method for tunable particle separation based on a combination of Deterministic Lateral Displacement (DLD) and Insulator Based Dielectrophoresis (I-DEP). Rather than deriving its tunability from its elastic properties[1], our present device uses an applied AC field to perturb the particle trajectories in the pressure-driven flow and is thereby capable of scanning the critical size over a range of factor two. Potential benefits include: extended dynamic range, facilitated fabrication and less clogging for given particle sizes, and combination of the precision afforded by DLD with the versatility of DEP.
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| 25. |
- Beech, Jason P., et al.
(författare)
-
Tunable separation and DNA manipulation in metal coated pillar arrays
- 2018
-
Ingår i: 22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2018. - 9781510897571 ; 4, s. 2090-2093
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Konferensbidrag (refereegranskat)abstract
- Implementing electrically connected metal-coated posts in a Deterministic Lateral Displacement (DLD) device and applying electric fields, we use electrokinetics to achieve tunable particle separations and to trap and manipulate DNA. The strength of DLD stems from its typically binary behavior. Particles move in one out of two trajectories based on their effective size. For particles that are close to the threshold size, a minute external force is sufficient to nudge the particles from one trajectory to another. Dielectrophoresis (DEP) provides such a force and also gives specificity based on the dielectric properties of the particles.
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| 26. |
- Beech, Jason P, et al.
(författare)
-
Using symmetry to control viscoelastic waves in pillar arrays
- 2023
-
Ingår i: RSC Advances. - 2046-2069. ; 13:45, s. 31497-31506
-
Tidskriftsartikel (refereegranskat)abstract
- Solutions of macromolecules exhibit viscoelastic properties and unlike Newtonian fluids, they may break time-reversal symmetry at low Reynolds numbers resulting in elastic turbulence. Furthermore, under some conditions, instead of the chaotic turbulence, the result is large-scale waves in the form of cyclic spatial and temporal concentration variations, as has been shown for macromolecular DNA flowing in microfluidic pillar arrays. We here demonstrate how altering the symmetry of the individual pillars can be used to influence the symmetry of these waves. We control the extent of instabilities in viscoelastic flow by leveraging the effects of the symmetry of the pillars on the waves, demonstrating suppressed viscoelastic fluctuations with relevance for transport and sorting applications, or conversely opening up for enhanced viscoelasticity-mediated mixing. The onset of waves, which changes flow resistance, occurs at different Deborah numbers for flow in different directions through the array of triangular pillars, thus breaking the symmetry of the flow resistance along the device, opening up for using the occurrence of the waves to construct a fluidic diode.
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| 27. |
- Beech, Jason, et al.
(författare)
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Sorting cells by size, shape and deformability
- 2012
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 12, s. 1048-1051
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Tidskriftsartikel (refereegranskat)abstract
- While size has been widely used as a parameter in cellular separations, in this communication we show how shape and deformability, a mainly untapped source of specificity in preparative and analytical microfluidic devices can be measured and used to separate cells. © 2012 The Royal Society of Chemistry.
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| 28. |
- Beech, Jason, et al.
(författare)
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Stretching the limits of separation
- 2006
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Ingår i: Book of abstracts: Intl Conf on Nanosci and Technol, Basel, Switzerland (2006).
-
Konferensbidrag (refereegranskat)
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| 29. |
- Beech, Jason, et al.
(författare)
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Tipping the balance of deterministic lateral displacement devices using dielectrophoresis.
- 2009
-
Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 9:18, s. 2698-2706
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Tidskriftsartikel (refereegranskat)abstract
- We report the use of dielectrophoresis (DEP) to achieve tunability, improve dynamic range and open up for the separation of particles with regard to parameters other than hydrodynamic size in deterministic lateral displacement (DLD) devices. DLD devices have been shown capable of rapidly and continuously separating micrometer sized plastic spheres by size with a resolution of 20 nm in diameter and of being able to handle the separation of biological samples as wide ranging as bacterial artificial chromosomes and blood cells. DEP, while not exhibiting the same resolution in size separation as DLD, has the benefit of being easy to tune and can, by choosing the frequency, be used to probe a variety of particle properties. By combining DLD and DEP we open up for the advantages, while avoiding the drawbacks, of the two techniques. We present a proof of principle in which the critical size for separation of polystyrene beads is tuned in the range 2-6 microm in a single device by the application of moderate (100 V cm(-1)), low frequency (100 Hz) AC electric fields. The behaviour of the device was further investigated by performing simulations of particle trajectories, the results of which were in good qualitative agreement with experiments, indicating the potential of the method for tunable, high-resolution separations with respect to both size and polarisability.
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| 30. |
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| 31. |
- Beech, Jason, et al.
(författare)
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Tuneable separation in elastomeric microfluidics devices.
- 2008
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 8:5, s. 657-659
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Tidskriftsartikel (refereegranskat)abstract
- We describe how the elastomeric properties of PDMS (polydimethylsiloxane) can be utilised to achieve tuneable particle separation in Deterministic Lateral Displacement devices via strain controlled alteration of inter-obstacle distances, a development that opens up new avenues toward more effective separation of particles in microfluidics devices.
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| 32. |
- Berg, Alexander, et al.
(författare)
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Growth parameter design for homogeneous material composition in ternary GaxIn1-xP nanowires.
- 2015
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 26:43
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Tidskriftsartikel (refereegranskat)abstract
- Ternary nanowires (NWs) often exhibit varying material composition along the NW growth axis because of different diffusion properties of the precursor molecules. This constitutes a problem for optoelectronic devices for which a homogeneous material composition is most often of importance. Especially, ternary GaInP NWs grown under a constant Ga-In precursor ratio typically show inhomogeneous material composition along the length of the NW due to the complexity of low temperature precursor pyrolysis and relative rates of growth species from gas phase diffusion and surface diffusion that contribute to synthesis of particle-assisted growth. Here, we present the results of a method to overcome this challenge by in situ tuning of the trimethylindium molar fraction during growth of ternary Zn-doped GaInP NWs. The NW material compositions were determined by use of x-ray diffraction, scanning transmission electron microscopy and energy dispersive x-ray spectroscopy and the optical properties by photoluminescence spectroscopy.
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| 33. |
- Bogas, Diana, et al.
(författare)
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Applications of optical DNA mapping in microbiology
- 2017
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Ingår i: BioTechniques. - : Future Science Ltd. - 0736-6205 .- 1940-9818. ; 62:6, s. 255-267
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Forskningsöversikt (refereegranskat)abstract
- Optical mapping (OM) has been used in microbiology for the past 20 years, initially as a technique to facilitate DNA sequence-based studies; however, with decreases in DNA sequencing costs and increases in sequence output from automated sequencing platforms, OM has grown into an important auxiliary tool for genome assembly and comparison. Currently, there are a number of new and exciting applications for OM in the field of microbiology, including investigation of disease outbreaks, identification of specific genes of clinical and/or epidemiological relevance, and the possibility of single-cell analysis when combined with cell-sorting approaches. In addition, designing lab-on-a-chip systems based on OM is now feasible and will allow the integrated and automated microbiological analysis of biological fluids. Here, we review the basic technology of OM, detail the current state of the art of the field, and look ahead to possible future developments in OM technology for microbiological applications.
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| 34. |
- Chen, Yang, et al.
(författare)
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Semiconductor nanowire array for transparent photovoltaic applications
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:19
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Tidskriftsartikel (refereegranskat)abstract
- The surface area of a building that could potentially be used for Building Integrated Photovoltaics would increase dramatically with the availability of transparent solar cells that could replace windows. The challenge is to capture energy from outside the visible region (UV or IR) while simultaneously allowing a high-quality observation of the outside world and transmitting sufficient light in the visible region to satisfactorily illuminate the interior of the building. In this paper, we show both computationally and experimentally that InP nanowire arrays can have good transparency in the visible region and high absorption in the near-infrared region. We show experimentally that we can achieve mean transparencies in the visible region of 65% and the radiative limit of more than 10% based on measured absorption and calculated emission. Our results demonstrate that nanowire arrays hold promise as a method to achieve transparent solar cells, which would fulfill the requirements to function as windows. In addition, we show that by optical design and by designing the geometry of nanowire arrays, solar cells can be achieved that absorb/transmit at wavelengths that are not decided by the bandgap of the material and that can be tailored to specific requirements such as colorful windows.
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| 35. |
- Ghasemi, Masoomeh, et al.
(författare)
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Separation of deformable hydrogel microparticles in deterministic lateral displacement devices
- 2012
-
Ingår i: Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012. - 9780979806452 ; , s. 1672-1674
-
Konferensbidrag (refereegranskat)abstract
- To better understand how deformable and non-spherical particles behave in sorting devices based on deterministic lateral displacement we generate models of biological particles with tunable size, shape and mechanical properties using stop-flow lithography and we explore how these parameters play a role in our separation devices. Hollow and solid cylinders are compared with respect to their deformability and their overall behavior in the device. Future work will expand the approach to a range of particle shapes and to particles with varied hydrogel composition to independently control the mechanical properties of the material.
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| 36. |
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| 37. |
- Henry, Ewan, et al.
(författare)
-
Sorting cells by their dynamical properties
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Recent advances in cell sorting aim at the development of novel methods that are sensitive to various mechanical properties of cells. Microfluidic technologies have a great potential for cell sorting; however, the design of many micro-devices is based on theories developed for rigid spherical particles with size as a separation parameter. Clearly, most bioparticles are non-spherical and deformable and therefore exhibit a much more intricate behavior in fluid flow than rigid spheres. Here, we demonstrate the use of cells' mechanical and dynamical properties as biomarkers for separation by employing a combination of mesoscale hydrodynamic simulations and microfluidic experiments. The dynamic behavior of red blood cells (RBCs) within deterministic lateral displacement (DLD) devices is investigated for different device geometries and viscosity contrasts between the intra-cellular fluid and suspending medium. We find that the viscosity contrast and associated cell dynamics clearly determine the RBC trajectory through a DLD device. Simulation results compare well to experiments and provide new insights into the physical mechanisms which govern the sorting of non-spherical and deformable cells in DLD devices. Finally, we discuss the implications of cell dynamics for sorting schemes based on properties other than cell size, such as mechanics and morphology.
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| 38. |
- Ho, Bao D., et al.
(författare)
-
Cell sorting using electrokinetic deterministic lateral displacement
- 2020
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- We show that by combining deterministic lateral displacement (DLD) with electrokinetics, it is possible to sort cells based on differences in their membrane and/or internal structures. Using heat to deactivate cells, which change their viability and structure, we then demonstrate sorting of a mixture of viable and non-viable cells for two different cell types. For Escherichia coli, the size change due to deactivation is insufficient to allow size-based DLD separation. Our method instead leverages the considerable change in zeta potential to achieve separation at low frequency. Conversely, for Saccharomyces cerevisiae (Baker’s yeast) the heat treatment does not result in any significant change of zeta potential. Instead, we perform the sorting at higher frequency and utilize what we believe is a change in dielectrophoretic mobility for the separation. We expect our work to form a basis for the development of simple, low-cost, continuous label-free methods that can separate cells and bioparticles based on their intrinsic properties.
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| 39. |
- Ho, Bao D., et al.
(författare)
-
Charge-based separation of micro-and nanoparticles
- 2020
-
Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- Deterministic Lateral Displacement (DLD) is a label-free particle sorting method that separates by size continuously and with high resolution. By combining DLD with electric fields (eDLD), we show separation of a variety of nano and micro-sized particles primarily by their zeta potential. Zeta potential is an indicator of electrokinetic charge—the charge corresponding to the electric field at the shear plane—an important property of micro-and nanoparticles in colloidal or separation science. We also demonstrate proof of principle of separation of nanoscale liposomes of different lipid compositions, with strong relevance for biomedicine. We perform careful characterization of relevant experimental conditions necessary to obtain adequate sorting of different particle types. By choosing a combination of frequency and amplitude, sorting can be made sensitive to the particle subgroup of interest. The enhanced displacement effect due to electrokinetics is found to be significant at low frequency and for particles with high zeta potential. The effect appears to scale with the square of the voltage, suggesting that it is associated with either non-linear electrokinetics or dielectrophoresis (DEP). However, since we observe large changes in separation behavior over the frequency range at which DEP forces are expected to remain constant, DEP can be ruled out.
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| 40. |
- Ho, Bao D., et al.
(författare)
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Combining electrokinetics with deterministic lateral displacement
- 2016
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Ingår i: 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016. - 9780979806490 ; , s. 1559-1560
-
Konferensbidrag (refereegranskat)abstract
- We make Deterministic Lateral Displacement (DLD) flexible by combining it with AC electrokinetics.
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| 41. |
- Ho, Bao D., et al.
(författare)
-
High throughput extracellular vesicle sorting using electrokinetic deterministic lateral displacement
- 2020
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Ingår i: MicroTAS 2020 - 24th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419017 ; , s. 637-638
-
Konferensbidrag (refereegranskat)abstract
- We present a microfluidic device that can sort nanosized extracellular vesicles (EVs) based on electrokinetics and Deterministic Lateral Displacement (DLD). The device is made from PDMS using standard soft-lithography, can separate particles down to 200 nm, and what is more, can achieve almost two orders of magnitude higher throughput than an otherwise single electrokinetic DLD device.
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| 42. |
- Ho, Bao D., et al.
(författare)
-
Viable/non-viable cell assay using electrokinetic deterministic lateral displacement
- 2019
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Ingår i: 23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2019. - 9781733419000 ; , s. 596-597
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Konferensbidrag (refereegranskat)abstract
- To evaluate the effect of antibiotic drugs, it is important that the cells that are killed can be sorted from the cells that are resistant to the antibiotics. Here we report a simple label-free method for the continuous separation of viable/non-viable cells using Electrokinetic Deterministic Lateral Displacement. In general, this opens up for continuous sorting of a population of cells that is homogeneous in size but heterogeneous in surface charge or dielectric properties, properties that change as a function of viability.
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| 43. |
- Hochstetter, Axel, et al.
(författare)
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Deterministic Lateral Displacement : Challenges and Perspectives
- 2020
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 14:9, s. 10784-10795
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Forskningsöversikt (refereegranskat)abstract
- The advent of microfluidics in the 1990s promised a revolution in multiple industries from healthcare to chemical processing. Deterministic lateral displacement (DLD) is a continuous-flow microfluidic particle separation method discovered in 2004 that has been applied successfully and widely to the separation of blood cells, yeast, spores, bacteria, viruses, DNA, droplets, and more. Deterministic lateral displacement is conceptually simple and can deliver consistent performance over a wide range of flow rates and particle concentrations. Despite wide use and in-depth study, DLD has not yet been fully elucidated or optimized, with different approaches to the same problem yielding varying results. We endeavor here to provide up-to-date expert opinion on the state-of-art and current fundamental, practical, and commercial challenges with DLD as well as describe experimental and modeling opportunities. Because these challenges and opportunities arise from constraints on hydrodynamics, fabrication, and operation at the micro- and nanoscale, we expect this Perspective to serve as a guide for the broader micro- and nanofluidic community to identify and to address open questions in the field.
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| 44. |
- Holm, Stefan H., et al.
(författare)
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A high-throughput deterministic lateral displacement device for rapid and sensitive field-diagnosis of sleeping sickness
- 2012
-
Ingår i: Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012. - 9780979806452 ; , s. 530-532
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Konferensbidrag (refereegranskat)abstract
- We present a simple and rapid microfluidic device capable of extracting and concentrating the parasite causing the fatal disease sleeping sickness (SS) from blood. The device is based on deterministic lateral displacement (DLD) and constructed with a single inlet with flow induced by an ordinary syringe. The simplicity is crucial as the device is intended for use in the resource depraved areas where the disease is endemic. With only one inlet an intricate design with multiple depths has been utilized to create a cell free stream from the blood plasma into which the parasites are forced and subsequently collected in a detection region. In order to maximize the sample volume up to 10 device layers were stacked on top of each other which resulted in a throughput of ∼10 μL/min. This allowed for an approximate time per test of below 15 min.
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| 45. |
- Holm, Stefan H., et al.
(författare)
-
Combined density and size-based sorting in deterministic lateral displacement devices
- 2013
-
Ingår i: 17th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2013. - 9781632666246 ; 2, s. 1224-1226
-
Konferensbidrag (refereegranskat)abstract
- We present a deterministic-lateral-displacement (DLD) device that extends the capabilities of this traditionally sizebased particle separation technique to also be sensitive to density. By the use of T-shaped posts instead of the normally cylindrical posts the particle trajectory through the device will be a function of its vertical position which in turn is determined by the buoyancy of the particles. The potential lies in fast sorting of complex biological samples together with diagnosis and treatment-monitoring of diseases affecting cell-density, eg. cancer, sickle-cell anemia and malaria. We demonstrate proof-of-principle of combined size-and-density-based sorting, specifically particles of identical size but different density.
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| 46. |
- Holm, Stefan H., et al.
(författare)
-
Density-based particle fractionation
- 2014
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Ingår i: 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014. - 9780979806476 ; , s. 288-290
-
Konferensbidrag (refereegranskat)abstract
- We present a label-free method capable of rapidly sorting particles based on their densities. Our device relies on deterministic lateral displacement (DLD) and achieves density fractionation by the use of T-shaped posts. By combining it with a lateral density gradient we achieve a density separation that is independent of size within a range given by the device geometry. Herein we present a proof-of-principle method which, in comparison to traditional density-separation techniques, is suitable for lab-on-a-chip environment.
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| 47. |
- Holm, Stefan H., et al.
(författare)
-
Microfluidic Particle Sorting in Concentrated Erythrocyte Suspensions
- 2019
-
Ingår i: Physical Review Applied. - 2331-7019. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- An important step in diagnostics is the isolation of specific cells and microorganisms of interest from blood. Since such bioparticles are often present at very low concentrations, throughput needs to be as high as possible. In addition, to ensure simplicity, a minimum of sample preparation is important. Therefore, sorting schemes that function for whole blood are highly desirable. Deterministic lateral displacement (DLD) devices have proven to be very precise and versatile in terms of a wide range of sorting parameters. To better understand how DLD devices perform for blood as the hematocrit increases, we carry out measurements and simulations for spherical particles in the micrometer range which move through DLD arrays for different flow velocities and hematocrits ranging from pure buffer to concentrated erythrocyte suspensions mimicking whole blood. We find that the separation function of the DLD array is sustained even though the blood cells introduce a shift in the trajectories and a significant dispersion for particles whose diameters are close to the critical size in the device. Simulations qualitatively replicate our experimental observations and help us identify fundamental mechanisms for the effect of hematocrit on the performance of the DLD device.
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| 48. |
- Holm, Stefan H., et al.
(författare)
-
Multiple depths in a deterministic lateral displacement device for field-diagnosis of sleeping-sickness
- 2011
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Ingår i: 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2011, MicroTAS 2011. - 9781618395955 ; 1, s. 527-529
-
Konferensbidrag (refereegranskat)abstract
- We present a simple and inexpensive device capable of extracting and concentrating the parasite causing sleeping sickness from blood. The device is aimed at being used in rural resource depraved areas where the disease is endemic; therefore simplicity is of paramount importance. The device is based on deterministic lateral displacement with a single inlet and flow induced by a syringe. Through an intricate design with multiple depths, a cell free stream is created from the blood plasma into which the parasites are guided and subsequently collected in a dedicated reservoir for observation.
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| 49. |
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| 50. |
- Holm, Stefan, et al.
(författare)
-
Separation of parasites from human blood using deterministic lateral displacement.
- 2011
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 11:Online February 2011, s. 1326-1332
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Tidskriftsartikel (refereegranskat)abstract
- We present the use of a simple microfluidic technique to separate living parasites from human blood. Parasitic trypanosomatids cause a range of human and animal diseases. African trypanosomes, responsible for human African trypanosomiasis (sleeping sickness), live free in the blood and other tissue fluids. Diagnosis relies on detection and due to their often low numbers against an overwhelming background of predominantly red blood cells it is crucial to separate the parasites from the blood. By modifying the method of deterministic lateral displacement, confining parasites and red blood cells in channels of optimized depth which accentuates morphological differences, we were able to achieve separation thus offering a potential route to diagnostics.
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