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1.
Lab Chip ; 19(17): 2811-2821, 2019 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-31312819

RESUMO

Microalgae cells have been recognized as a promising sustainable resource to meet worldwide growing demands for renewable energy, food, livestock feed, water, cosmetics, pharmaceuticals, and materials. In order to ensure high-efficiency and high-quality production of biomass, biofuel, or bio-based products, purification procedures prior to the storage and cultivation of the microalgae from contaminated bacteria are of great importance. The present work proposed and developed a simple, sheathless, and efficient method to separate microalgae Chlorella from bacteria Bacillus Subtilis in a straight channel using the viscoelasticity of the medium. Microalgae and bacteria migrate to different lateral positions closer to the channel centre and channel walls respectively. Fluorescent microparticles with 1 µm and 5 µm diameters were first used to mimic the behaviours of bacteria and microalgae to optimize the separating conditions. Subsequently, size-based separation in Newtonian fluid and in viscoelastic fluid in straight channels with different aspect ratios was compared and demonstrated. Under the optimal condition, the removal ratio for 1 µm microparticles and separation efficiency for 5 µm particles can reach up to 98.28% and 93.85% respectively. For bacteria and microalgae cells separation, the removal ratio for bacteria and separation efficiency for microalgae cells is 92.69% and 100% respectively. This work demonstrated the continuous and sheathless separation of microalgae from bacteria for the first time by viscoelastic microfluidics. This technique can also be applied as an efficient and user-friendly method to separate mammalian cells or other kinds of cells.

2.
Nat Commun ; 10(1): 1300, 2019 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-30899009

RESUMO

Conductive elastic composites have been used widely in soft electronics and soft robotics. These composites are typically a mixture of conductive fillers within elastomeric substrates. They can sense strain via changes in resistance resulting from separation of the fillers during elongation. Thus, most elastic composites exhibit a negative piezoconductive effect, i.e. the conductivity decreases under tensile strain. This property is undesirable for stretchable conductors since such composites may become less conductive during deformation. Here, we report a liquid metal-filled magnetorheological elastomer comprising a hybrid of fillers of liquid metal microdroplets and metallic magnetic microparticles. The composite's resistivity reaches a maximum value in the relaxed state and drops drastically under any deformation, indicating that the composite exhibits an unconventional positive piezoconductive effect. We further investigate the magnetic field-responsive thermal properties of the composite and demonstrate several proof-of-concept applications. This composite has prospective applications in sensors, stretchable conductors, and responsive thermal interfaces.

3.
Anal Chem ; 91(5): 3725-3732, 2019 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-30747514

RESUMO

Although droplet-based microfluidics has been broadly used as a versatile tool in biology, chemistry, and nanotechnology, its rather complicated microfabrication process and the requirement of specialized hardware and operating skills hinder researchers fully unleashing the potential of this powerful platform. Here, we develop an integrated microdroplet generator enabled by a spinning conical frustum for the versatile production of near-monodisperse microdroplets in a high-throughput and off-chip manner. The construction and operation of this generator are simple and straightforward without the need of microfabrication, and we demonstrate that the generator is able to passively and actively control the size of the produced microdroplets. In addition to water microdroplets, this generator can produce microdroplets of liquid metal that would be difficult to produce in conventional microfluidic platforms as liquid metal has high surface tension. Moreover, we demonstrate that this generator can produce solid hydrogel microparticles and fibers using integrated ultraviolet (UV) light. In the end, we further explore the ability of this generator for forming double emulsions by coflowing two immiscible liquids. Given the remarkable abilities demonstrated by this platform and the tremendous potential of microdroplets, this user-friendly method may revolutionize the future of droplet-based chemical synthesis and biological analysis.

4.
Anal Chem ; 91(6): 4077-4084, 2019 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-30669838

RESUMO

Focusing and separation of particles such as cells at high throughput is extremely attractive for biomedical applications. Particle manipulation based on inertial effects requires a high flow speed and thus is well-suited to high-throughput applications. Recently, inertial focusing and separation using curvilinear microchannels has been attracting a great amount of interest because of the linear structure for parallelization, small device footprint, superior particle-focusing performance, and easy implementation of particle separation. However, the curvature directions of these microchannels alternate, leading to variations in both the magnitude and direction of the induced secondary flow. Accumulation of this variation along the channel causes unpredictable behaviors of particles. This paper systematically investigates the inertial-focusing phenomenon in low-aspect-ratio symmetric sinusoidal channels. First, we comprehensively studied the effects of parameters such as viscosity, flow conditions, particle size, and geometric dimensions of the microchannel on differential particle focusing. We found that particle inertial focusing is generally independent of fluid kinematic viscosity but highly dependent on particle size, flow conditions, and channel dimensions. Next, we derived an explicit scaling factor and included all four dimensionless parameters (particle-blockage ratio, curvature ratio, Dean number, and channel aspect ratio) in a single operational map to illustrate the particle-focusing patterns. Finally, we proposed a rational guideline to intuitively instruct the design of channel dimensions for separation of a given particle mixture.

5.
Small ; 14(21): e1800118, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29682878

RESUMO

Functional nanoparticles comprised of liquid metals, such as eutectic gallium indium (EGaIn) and Galinstan, present exciting opportunities in the fields of flexible electronics, sensors, catalysts, and drug delivery systems. Methods used currently for producing liquid metal nanoparticles have significant disadvantages as they rely on both bulky and expensive high-power sonication probe systems, and also generally require the use of small molecules bearing thiol groups to stabilize the nanoparticles. Herein, an innovative microfluidics-enabled platform is described as an inexpensive, easily accessible method for the on-chip mass production of EGaIn nanoparticles with tunable size distributions in an aqueous medium. A novel nanoparticle-stabilization approach is reported using brushed polyethylene glycol chains with trithiocarbonate end-groups negating the requirements for thiol additives while imparting a "stealth" surface layer. Furthermore, a surface modification of the nanoparticles is demonstrated using galvanic replacement and conjugation with antibodies. It is envisioned that the demonstrated microfluidic technique can be used as an economic and versatile platform for the rapid production of liquid metal-based nanoparticles for a range of biomedical applications.

6.
Electrophoresis ; 39(12): 1460-1465, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29543983

RESUMO

This work presents a simple, low-cost method to fabricate semi-circular channels using solder paste, which can amalgamate the cooper surface to form a half-cylinder mold using the surface tension of Sn-Pd alloy (the main component in solder paste). This technique enables semi-circular channels to be manufactured with different dimensions. These semi-circular channels will then be integrated with a polymethylmethacrylate frame and machine screws to create miniaturized, portable microfluidic valves for sequential liquid delivery and particle synthesis. This approach avoids complicated fabrication processes and expensive facilities and thus has the potential to be a useful tool for lab-on-a-chip applications.


Assuntos
Microfluídica , Ligas/química , Desenho de Equipamento/instrumentação , Dispositivos Lab-On-A-Chip , Paládio/química , Tensão Superficial , Estanho/química
7.
Biomed Microdevices ; 20(2): 23, 2018 02 23.
Artigo em Inglês | MEDLINE | ID: mdl-29476424

RESUMO

In this work, a novel double-layer microfluidic device for enhancing particle focusing was presented. The double-layer device consists of a channel with expansion-contraction array and periodical slanted grooves. The secondary flows induced by the grooves modulate the flow patterns in the expansion-contraction-array (ECA) channel, further affecting the particle migration. Compared with the single ECA channel, the double-layer channel can focus the particles over a wider range of flow rate. Due to the differentiation of lateral migration, the double-layer channel is able to distinguish the particles with different sizes. Furthermore, the equilibrium positions could be modulated by the orientation of grooves. This work demonstrates the possibility to enhance and adjust the inertial focusing in an ECA channel with the assistance of grooves, which may provide a simple and portable platform for downstream filtration, separation, and detection.


Assuntos
Dispositivos Lab-On-A-Chip , Tamanho da Partícula
8.
Lab Chip ; 18(5): 785-792, 2018 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-29424381

RESUMO

Numerous lab-on-a-chip applications benefit from channels with complex structures and configurations in the areas of tissue engineering and clinical diagnostics. The current fabrication approaches require time-consuming, complicated processes and bulky, expensive facilities. In this work, we propose a novel method for the fabrication of complex channels with the assistance of amalgamation of liquid metal with copper tape. This new technique enables the rapid fabrication of liquid metal molds with various dimensions and diverse structures. Two proof-of-concept experiments were conducted to verify the utilization of this method. First, the channel replicated from the liquid metal mold is used to enhance the mixing performance of liquids flowing through the channel. Second, a channel with a semicircular cross-section is fabricated to achieve 3D focusing in a simple way. This proposed technique can be readily used for fabricating complex channels for a wide range of applications.

9.
Electrophoresis ; 39(7): 957-964, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29292831

RESUMO

Proteinuria is an established risk marker for progressive renal function loss and patients would significantly benefit from a point-of-care testing. Although extensive work has been done to develop the microfluidic devices for the detection of urinary protein, they need the complicated operation and bulky peripherals. Here, we present a rapid, maskless 3D prototyping for fabrication of capillary fluidic circuits using laser engraving. The capillary circuits can be fabricated in a short amount of time (<10 min) without the requirements of clean-room facilities and photomasks. The advanced capillary components (e.g., trigger valves, retention valves and retention bursting valves) were fabricated, enabling the sequential liquid delivery and sample-reagent mixing. With the integration of smartphone-based detection platform, the microfluidic device can quantify the urinary protein via a colorimetric analysis. By eliminating the bulky and expensive equipment, this smartphone-based detection platform is portable for on-site quantitative detection.


Assuntos
Técnicas Analíticas Microfluídicas/métodos , Proteinúria/urina , Smartphone/instrumentação , Estereolitografia , Colorimetria/métodos , Desenho de Equipamento/instrumentação , Humanos , Imagem Óptica/instrumentação , Processos Fotoquímicos , Polimetil Metacrilato/química , Soroalbumina Bovina/química , Propriedades de Superfície
10.
Lab Chip ; 18(4): 551-567, 2018 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-29340388

RESUMO

Recently, research on particle migration in non-Newtonian viscoelastic fluids has gained considerable attention. In a viscoelastic fluid, three dimensional (3D) particle focusing can be easily realized in simple channels without the need for any external force fields or complex microchannel structures compared with that in a Newtonian fluid. Due to its promising properties for particle precise focusing and manipulation, this field has been developed rapidly, and research on the field has been shifted from fundamentals to applications. This review will elaborate the recent progress of particle migration in viscoelastic fluids, especially on the aspect of applications. The hydrodynamic forces on the micro/nano particles in viscoelastic fluids are discussed. Next, we elaborate the basic particle migration in viscoelasticity-dominant fluids and elasto-inertial fluids in straight channels. After that, a comprehensive review on the applications of viscoelasticity-induced particle migration (particle separation, cell deformability measurement and alignment, particle solution exchange, rheometry-on-a-chip and others) is presented; finally, we thrash out some perspectives on the future directions of particle migration in viscoelastic fluids.

11.
IEEE Trans Biomed Circuits Syst ; 11(6): 1422-1430, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28866599

RESUMO

White blood cells (WBCs) constitute only about 0.1% of human blood cells, yet contain rich information about the immune status of the body; thus, separation of WBCs from the whole blood is an indispensable and critical sample preparation step in many scientific, clinical, and diagnostic applications. In this paper, we developed a continuous and high-throughput microfluidic WBC separation platform utilizing the differential inertial focusing of particles in serpentine microchannels. First, separation performance of the proposed method is characterized and evaluated using polystyrene beads in the serpentine channel. The purity of 10-µm polystyrene beads is increased from 0.1% to 80.3% after two cascaded processes, with an average enrichment ratio of 28 times. Next, we investigated focusing and separation properties of Jurkat cells spiked in the blood to mimic the presence of WBCs in whole blood. Finally, separation of WBCs from human whole blood was conducted and separation purity of WBCs was measured by the flow cytometry. The results show that the purity of WBCs can be increased to 48% after two consecutive processes, with an average enrichment ratio of ten times. Meanwhile, a parallelized inertial microfluidic device was designed to provide a high processing flow rate of 288 ml/h for the diluted (×1/20) whole blood. The proposed microfluidic device can potentially work as an upstream component for blood sample preparation and analysis in the integrated microfluidic systems.


Assuntos
Leucócitos/citologia , Microfluídica/métodos , Separação Celular , Desenho de Equipamento/métodos , Humanos , Técnicas Analíticas Microfluídicas/métodos
12.
Anal Chem ; 89(17): 9574-9582, 2017 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-28787117

RESUMO

This work investigates the on-chip washing process of microparticles and cells using coflow configuration of viscoelastic fluid and Newtonian fluid in a straight microchannel. By adding a small amount of biocompatible polymers into the particle medium or cell culture medium, the induced viscoelasticity can push particles and cells laterally from their original medium to the coflow Newtonian medium. This behavior can be used for particle or cell washing. First, we demonstrated on-chip particle washing by the size-dependent migration speed using coflow of viscoelastic fluid and Newtonian fluid. The critical particle size for efficient particle washing was determined. Second, we demonstrated continuous on-chip washing of Jurkat cells using coflow of viscoelastic fluid and Newtonian fluid. The lateral migration process of Jurkat cells along the channel length was investigated. In addition, the cell washing quality was verified by hemocytometry and flow cytometry with a recovery rate as high as 92.8%. Scanning spectrophotometric measurements of the media from the two inlets and the two outlets demonstrated that diffusion of the coflow was negligible, indicating efficient cell washing from culture medium to phosphate-buffered saline medium. This technique may be a safer, simpler, cheaper, and more efficient alternative to the tedious conventional centrifugation methods and may open up a wide range of biomedical applications.

13.
IEEE Trans Biomed Circuits Syst ; 11(6): 1406-1412, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28809710

RESUMO

In this paper, we proposed a microparticle manipulation approach, by which particles are able to be guided to different equilibrium positions through modulating the Reynolds number. In the microchannel with arc-shaped groove arrays, secondary flow vortex arisen due to the pressure gradient varies in the aspects of both magnitude and shape with the increase of Reynolds number. And the variation of secondary flow vortex brings about different focusing modes of microparticles in the microchannel. We investigated the focusing phenomenon experimentally and analyzed the mechanism through numerical simulations. At a high Reynolds number (Re = 127.27), the geometry-induced secondary flow rotates constantly along a direction, and most particles are guided to the equilibrium position near one side of the microchannel. However, at a low Reynolds number (Re = 2.39), the shapes of geometry-induced secondary flow vortices are obviously different, forming a variant Dean-like vortex that consists of two asymmetric counter-rotating streams in cross sections of the straight channel. Because of the periodical effects, suspended particles are concentrated at another equilibrium position on the opposite side of the microchannel. Meanwhile, the effects of particle size influence both the focusing position and quality in regimes.


Assuntos
Técnicas Analíticas Microfluídicas/métodos , Tamanho da Partícula
14.
Sci Rep ; 7: 41153, 2017 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-28112225

RESUMO

Sheathless particle focusing which utilises the secondary flow with a high throughput has great potential for use in microfluidic applications. In this work, an innovative particle focusing method was proposed. This method makes use of a mechanism that takes advantage of secondary flow and inertial migration. The device was a straight channel with arrays of arc-shaped grooves on the top surface. First, the mechanism and expected focusing phenomenon are explained using numerical simulation of the flow field and force balance. A simulation of particle trajectories was conducted as a reference, and then a series of experiments was designed and the effects of changes in particle size, flow rate and quantity of the groove structure were discussed. The microscopic images show that this particle focusing method performed well for different size particles, and the results agreed well with the theory and simulated results. Finally, the channel successfully concentrated Jurkat cells, which showed a good compatibility in the biological assay field. In this work, the arc-shaped groove channel was demonstrated to have the ability to achieve high-throughput, sheathless and three-dimensional particle focusing with simple operations.

15.
Micromachines (Basel) ; 8(11)2017 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-30400505

RESUMO

In the capillary venules, blood cells auto-separate with red blood cells aggregating near the centre of vessel and the nucleated cells marginating toward the wall of vessel. In this experiment, we used cell margination to help enrich the Jurkat cells via a groove-based channel which provides a vertical expansion-contraction structure, wherein the red blood cells invade the grooves and push the Jurkat cells to the bottom of the channel. The secondary flows induced by the anisotropic grooves bring the Jurkat cells to the right sidewall. Rigid, 13-µm diameter polystyrene particles were spiked into the whole blood to verify the operating principle under various working conditions, and then tests were carried out using Jurkat cells (~15 µm). The performance of this device was quantified by analysing the cell distribution in a transverse direction at the outlet, and then measuring the cell concentration from the corresponding outlets. The results indicate that Jurkat cells were enriched by 22.3-fold with a recovery rate of 83.4%, thus proving that this microfluidic platform provides a gentle and passive way to isolate intact and viable Jurkat cells.

16.
Lab Chip ; 16(20): 3947-3956, 2016 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-27722618

RESUMO

Separation of microparticles has found broad applications in biomedicine, industry and clinical diagnosis. In a conventional aqueous ferrofluid, separation of microparticles usually employs a sheath flow or two offset magnets to confine particle streams for downstream particle sorting. This complicates the fluid control, device fabrication, and dilutes the particle sample. In this work, we propose and develop a novel viscoelastic ferrofluid by replacing the Newtonian base medium of the conventional ferrofluid with non-Newtonian poly(ethylene oxide) (PEO) aqueous solution. The properties of both viscoelastic 3D focusing and negative magnetophoresis of the viscoelastic ferrofluid were verified and investigated. By employing the both properties in a serial manner, continuous and sheathless separation of nonmagnetic particles based on particle size has been demonstrated. This novel viscoelastic ferrofluid is expected to bring more flexibility and versatility to the design and functionality in microfluidic devices.


Assuntos
Dispositivos Lab-On-A-Chip , Campos Magnéticos , Microesferas , Desenho de Equipamento , Polietilenoglicóis/química
17.
Lab Chip ; 16(20): 3919-3928, 2016 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-27714019

RESUMO

In this paper, continuous plasma extraction under viscoelastic fluid in a straight channel with asymmetrical expansion-contraction cavity arrays (ECCA channel) is demonstrated by exploiting the Dean-flow-coupled elasto-inertial effects. First, the forces experienced by particles in the ECCA channel were discussed. Then, 4.8 µm diameter particles, which mimic the behaviour of red blood cells (RBCs), were used to study the effects of poly(ethylene oxide) (PEO) concentrations and flow rates on particle viscoelastic focusing. Also, 3 µm, 4.8 µm and 10 µm diameter particles, which are comparable in size to platelets, RBCs, and white blood cells (WBCs), respectively, were used to study the effect of particle size on particle viscoelastic focusing. Finally, plasma extraction from diluted blood samples under viscoelastic conditions was conducted, and the purity of the collected blood plasma was measured. After two series of filtration with the same ECCA channel, the purity of 3 µm, 4.8 µm and 10 µm diameter particles reached 100%, and the plasma purity reached 99.99%, as measured by a hemocytometer. In addition, flow cytometry data further validated the filtration performance of blood plasma. By exploiting the Dean-flow-coupled elasto-inertial effects, the ECCA channel offers a continuous, sheathless, and high purity plasma extraction.


Assuntos
Fracionamento Celular/instrumentação , Elasticidade , Dispositivos Lab-On-A-Chip , Plasma , Desenho de Equipamento , Humanos , Polietilenoglicóis/química , Viscosidade
18.
Electrophoresis ; 37(15-16): 2147-55, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27140330

RESUMO

In this work, particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid was experimentally investigated. The 4.8-µm micro-particles were dispersed in a polyethylene oxide (PEO) viscoelastic solution, and then the solution was injected into a straight rectangular channel with a deionised (DI) water Newtonian sheath flow. Micro-particles suspended in PEO solution migrated laterally to a DI water stream, but migration in the opposite direction from a DI water stream to a PEO solution stream or from one DI water stream to another DI water stream could not be achieved. The lateral migration of particles depends on the viscoelastic properties of the sample fluids. Furthermore, the effects of channel length, flow rate, and PEO concentration were studied. By using viscoelastic sample flow and Newtonian sheath flow, a selective particle lateral migration can be achieved in a simple straight channel, without any external force fields. This particle lateral migration technique could be potentially used in solution exchange fields such as automated cell staining and washing in microfluidic platforms, and holds numerous biomedical applications.


Assuntos
Técnicas Analíticas Microfluídicas/métodos , Microfluídica , Substâncias Viscoelásticas/química , Hidrodinâmica , Polietilenoglicóis
19.
Micromachines (Basel) ; 7(11)2016 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30404368

RESUMO

In this work, a novel microfluidic platform for tunable particle focusing in a straight channel with symmetric semicircle obstacle arrays using electrophoresis (EP)-modified inertial effects was presented. By exerting an EP force on the charged microparticles, a relative velocity gap between microspheres and fluid in a straight channel with symmetric semicircle obstacle arrays was implemented. The relative velocity and fluid shear will induce shear-slip lift force (Saffman lift force) perpendicular to the mainstream direction. Therefore, the focusing pattern can be altered using the electrophoresis-induced Saffman force. The effects of electric field direction, flow rate, electric field magnitude, and particle size were also studied. This demonstrates the possibility of adjusting the particle inertial focusing pattern in a straight channel with with symmetric semicircle obstacle arrays using electrophoresis. Manipulation of the lateral migration of focusing streaks increases controllability in applications such as blood cell filtration and the separation of cells by size.

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