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1.
Artigo em Inglês | MEDLINE | ID: mdl-32037788

RESUMO

Gallium-based room-temperature liquid metals have enormous potential for realizing various applications in electronic devices, heat flow management, and soft actuators. Filling narrow spaces with a liquid metal is of great importance in rapid prototyping and circuit printing. However, it is relatively difficult to stretch or spread liquid metals into desired patterns because of their large surface tension. Here, we propose a method to fabricate a particle-based porous material which can enable the rapid and spontaneous diffusion of liquid metals within the material under a capillary force. Remarkably, such a method can allow liquid metal to diffuse along complex structures and even overcome the effect of gravity despite their large densities. We further demonstrate that the developed method can be utilized for prototyping complex three-dimensional (3D) structures via direct casting and connecting individual parts or by 3D printing. As such, we believe that the presented technique holds great promise for the development of additive manufacturing, rapid prototyping, and soft electronics using liquid metals.

2.
Lab Chip ; 20(1): 35-53, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31720655

RESUMO

Sub-micrometer particles (0.10-1.0 µm) are of great significance to study, e.g., microvesicles and protein aggregates are targets for therapeutic intervention, and sub-micrometer fluorescent polystyrene (PS) particles are used as probes for diagnostic imaging. Focusing of sub-micrometer particles - precisely control over the position of sub-micrometer particles in a tightly focused stream - has a wide range of applications in the field of biology, chemistry and environment, by acting as a prerequisite step for downstream detection, manipulation and quantification. Microfluidic devices have been attracting great attention as desirable tools for sub-micrometer particle focusing, due to their small size, low reagent consumption, fast analysis and low cost. Recent advancements in fundamental knowledge and fabrication technologies have enabled microfluidic focusing of particles at sub-micrometer scale in a continuous, label-free and high-throughput manner. Microfluidic methods for the focusing of sub-micrometer particles can be classified into two main groups depending on whether an external field is applied: 1) passive methods, which utilize intrinsic fluidic properties without the need of external actuation, such as inertial, deterministic lateral displacement (DLD), viscoelastic and hydrophoretic focusing; and 2) active methods, where external fields are used, such as dielectrophoretic, thermophoretic, acoustophoretic and optical focusing. This article mainly reviews the studies on the focusing of sub-micrometer particles in microfluidic devices over the past 10 years. It aims to bridge the gap between the focusing of micrometer and nanometer scale (1.0-100 nm) particles and to improve the understanding of development progress, current advances and future prospects in microfluidic focusing techniques.

3.
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.

4.
Micromachines (Basel) ; 10(3)2019 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-30917484

RESUMO

Gallium-based liquid metal alloys have been attracting attention from both industry and academia as soft, deformable, reconfigurable and multifunctional materials in microfluidic, electronic and electromagnetic devices. Although various technologies have been explored to control the morphology of liquid metals, there is still a lack of methods that can achieve precise morphological control over a free-standing liquid metal droplet without the use of mechanical confinement. Electrochemical manipulation can be relatively easy to apply to liquid metals, but there is a need for techniques that can enable automatic and precise control. Here, we investigate the use of an electrochemical technique combined with a feedback control system to automatically and precisely control the morphology of a free-standing liquid metal droplet in a sodium hydroxide solution. We establish a proof-of-concept platform controlled by a microcontroller to demonstrate the reconfiguration of a liquid metal droplet to desired patterns. We expect that this method will be further developed to realize future reconfigurable liquid metal-enabled soft robots.

5.
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.

6.
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.

7.
IEEE J Biomed Health Inform ; 23(1): 66-71, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29994232

RESUMO

Nowadays, cardiovascular diseases have become one of the most risks threating human being's life in the world. The early screening and efficient management of cardiovascular diseases are critically important to extend the patients' life. Blood lipid level is a key biochemical factor used to estimate the cardiovascular disease in clinical situation. Triglyceride as one important blood lipid plays an indispensable role in the blood test. On the other hand, smartphone has unprecedentedly large scale users since the last decade, which paves the wide avenue for the dissemination of smartphone-associated medical devices. In this paper, we integrated the smartphone with the Triglyceride (TG) sensory module to monitor the finger pricked whole blood TG at the point of care scale. The miniaturized electrochemical analyzer was immobilized on the main board of the smartphone which enables the smartphone work as the blood TG analyzer incorporating with the disposable electrochemical TG test strip. The blood TG measured by the medical smartphone was compared to the results obtained from the conventional bulky biochemical analyzer with acceptable accuracy, which demonstrated that the proposed medical smartphone is capable of providing a point of care analytical device for blood TC monitoring at the medical level. Its potential in cardiovascular disease prevention and management was believed to be great, since the proposed system is ultracompact, smart, cost effective, reliable, and flexible with medical data acquisition.


Assuntos
Análise Química do Sangue/instrumentação , Doenças Cardiovasculares/prevenção & controle , Sistemas Automatizados de Assistência Junto ao Leito , Smartphone , Triglicerídeos/sangue , Análise Química do Sangue/métodos , Doenças Cardiovasculares/sangue , Desenho de Equipamento , Humanos
8.
Adv Mater ; 30(51): e1805039, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30318653

RESUMO

The controlled actuation of gallium liquid-metal (LM) alloys has presented new and exciting opportunities for constructing mobile robots with structural flexibility. However, the locomotion of current LM-based actuators often relies on inducing a gradient of interfacial tension on the LM surface within electrolytes, which limits their application outside a liquid environment. In this work, a wheeled robot using a LM droplet as the core of the driving system is developed that enables it to move outside liquid environment. The LM droplet inside the robot is actuated using a voltage to alter the robot's center of gravity, which in turn generates a rolling torque and induces continuous locomotion at a steady speed. A series of experiments is carried out to examine the robot's performance and then to develop a dynamic model using the Lagrange method to understand the locomotion. An untethered and self-powered wheeled robot that utilizes mini-lithium-batteries is also demonstrated. This study is envisaged to have the potential to expand current research on LM-based actuators to realize future complex robotic systems.

9.
Nanoscale ; 10(42): 19871-19878, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30335111

RESUMO

Gallium-based liquid metals are attractive due to their unique combination of metallic and fluidic properties. Liquid metal nanoparticles (LM NPs), produced readily using sonication, find use in soft electronics, drug delivery, and other applications. However, LM NPs in aqueous solutions tend to oxidize and precipitate over time, which hinders their utility in systems that require long-term stability. Here, we introduce a facile route to rapidly produce an aqueous suspension of stable LM NPs within five minutes. We accomplish this by dissolving poly(1-octadecene-alt-maleic anhydride) (POMA) in toluene and mixing with deionized water in the presence of a liquid metal (LM). Sonicating the mixture results in the formation of toluene-POMA emulsions that embed the LM NPs; as the toluene evaporates, POMA coats the particles. Due to the POMA hydrophobic coating, the LM NPs remain stable in biological buffers for at least 60 days without noticeable oxidation, as confirmed by dynamic light scattering and transmission electron microscopy. Further stabilization is achieved by tuning the LM composition. This paper elucidates the stabilization mechanisms. The stable LM NPs possess the potential to advance the use of LM in biomedical applications.

10.
Soft Matter ; 14(35): 7113-7118, 2018 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-30182111

RESUMO

The locomotion of liquid metal droplets enables enormous potential for realizing various applications in microelectromechanical systems (MEMSs), biomimetics, and microfluidics. However, current techniques for actuating liquid metal droplets are either associated with intense electrochemical reactions or require modification of their physical properties by coating/mixing them with other materials. These methods either generate gas bubbles or compromise the stability and liquidity of the liquid metal. Here, we introduce an innovative method for controlling the locomotion of liquid metal droplets using Lorentz force induced by magnetic fields. Remarkably, utilizing a magnetic field to induce actuation avoids the generation of gas bubbles in comparison to the method of forming a surface tension gradient on the liquid metal using electrochemistry. In addition, the use of Lorentz force avoids the need of mixing liquid metals with ferromagnetic materials, which may compromise the liquidity of liquid metals. Most importantly, we discover that the existence of a slip layer for liquid metal droplets distinguishes their actuation behaviors from solid metallic spheres. We investigate the parameters affecting the actuation behavior of liquid metal droplets and explore the science behind its operation. We further conducted a series of proof-of-concept experiments to verify the controllability of our method for actuating liquid metal droplets. As such, we believe that the presented technique represents a significant advance in comparison to reported actuation methods for liquid metals, and possesses the potential to be readily adapted by other systems to advance the fields of MEMS actuation and soft robotics.

11.
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.

12.
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
13.
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
14.
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.

15.
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
16.
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.

17.
Proc Natl Acad Sci U S A ; 114(33): 8728-8733, 2017 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-28760972

RESUMO

Although the elementary unit of biology is the cell, high-throughput methods for the microscale manipulation of cells and reagents are limited. The existing options either are slow, lack single-cell specificity, or use fluid volumes out of scale with those of cells. Here we present printed droplet microfluidics, a technology to dispense picoliter droplets and cells with deterministic control. The core technology is a fluorescence-activated droplet sorter coupled to a specialized substrate that together act as a picoliter droplet and single-cell printer, enabling high-throughput generation of intricate arrays of droplets, cells, and microparticles. Printed droplet microfluidics provides a programmable and robust technology to construct arrays of defined cell and reagent combinations and to integrate multiple measurement modalities together in a single assay.


Assuntos
Técnicas Analíticas Microfluídicas/métodos , Microfluídica/métodos , Bioensaio/métodos , Contagem de Células/métodos , Linhagem Celular Tumoral , Humanos , Impressão/métodos
18.
Lab Chip ; 17(6): 974-993, 2017 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-28225135

RESUMO

Several gallium-based liquid metal alloys are liquid at room temperature. As 'liquid', such alloys have a low viscosity and a high surface tension while as 'metal', they have high thermal and electrical conductivities, similar to mercury. However, unlike mercury, these liquid metal alloys have low toxicity and a negligible vapor pressure, rendering them much safer. In comparison to mercury, the distinguishing feature of these alloys is the rapid formation of a self-limiting atomically thin layer of gallium oxide over their surface when exposed to oxygen. This oxide layer changes many physical and chemical properties of gallium alloys, including their interfacial and rheological properties, which can be employed and modulated for various applications in microfluidics. Injecting liquid metal into microfluidic structures has been extensively used to pattern and encapsulate highly deformable and reconfigurable electronic devices including electrodes, sensors, antennas, and interconnects. Likewise, the unique features of liquid metals have been employed for fabricating miniaturized microfluidic components including pumps, valves, heaters, and electrodes. In this review, we discuss liquid metal enabled microfluidic components, and highlight their desirable attributes including simple fabrication, facile integration, stretchability, reconfigurability, and low power consumption, with promising applications for highly integrated microfluidic systems.

19.
Sci Rep ; 7: 40479, 2017 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-28091583

RESUMO

The emerging development of the hybrid plasmonic waveguide has recently received significant attention owing to its remarkable capability of enabling subwavelength field confinement and great transmission distance. Here we report a guiding approach that integrates hybrid plasmon polariton with dielectric-loaded plasmonic waveguiding. By introducing a deep-subwavelength dielectric ridge between a dielectric slab and a metallic substrate, a hybrid dielectric-loaded nanoridge plasmonic waveguide is formed. The waveguide features lower propagation loss than its conventional hybrid waveguiding counterpart, while maintaining strong optical confinement at telecommunication wavelengths. Through systematic structural parameter tuning, we realize an efficient balance between confinement and attenuation of the fundamental hybrid mode, and we demonstrate the tolerance of its properties despite fabrication imperfections. Furthermore, we show that the waveguide concept can be extended to other metal/dielectric composites as well, including metal-insulator-metal and insulator-metal-insulator configurations. Our hybrid dielectric-loaded nanoridge plasmonic platform may serve as a fundamental building block for various functional photonic components and be used in applications such as sensing, nanofocusing, and nanolasing.


Assuntos
Eletricidade , Luz , Nanopartículas/química , Silício/química
20.
Artigo em Inglês | MEDLINE | ID: mdl-29358901

RESUMO

The precise manipulation of acoustic fields in microfluidics is of critical importance for the realization of many biomedical applications. Despite the tremendous efforts devoted to the field of acoustofluidics during recent years, dexterous control, with an arbitrary and complex acoustic wavefront, in a prescribed, microscale region is still out of reach. Here, we introduce the concept of acoustofluidic waveguide, a three-dimensional compact configuration that is capable of locally guiding acoustic waves into a fluidic environment. Through comprehensive numerical simulations, we revealed the possibility of forming complex field patterns with defined pressure nodes within a highly localized, pre-determined region inside the microfluidic chamber. We also demonstrated the tunability of the acoustic field profile through controlling the size and shape of the waveguide geometry, as well as the operational frequency of the acoustic wave. The feasibility of the waveguide concept was experimentally verified via microparticle trapping and patterning. Our acoustofluidic waveguiding structures can be readily integrated with other microfluidic configurations and can be further designed into more complex types of passive acoustofluidic devices. The waveguide platform provides a promising alternative to current acoustic manipulation techniques and is useful in many applications such as single-cell analysis, point-of-care diagnostics, and studies of cell-cell interactions.

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