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Showing papers on "Microfluidics published in 2019"


Journal ArticleDOI
TL;DR: A conductive liquid membrane is used as a permeable electrode to demonstrate triboelectrification via liquid–liquid contact by passing liquid droplets through a liquid membrane to generate power.
Abstract: Triboelectric nanogenerators are an energy harvesting technology that relies on the coupling effects of contact electrification and electrostatic induction between two solids or a liquid and a solid. Here, we present a triboelectric nanogenerator that can work based on the interaction between two pure liquids. A liquid–liquid triboelectric nanogenerator is achieved by passing a liquid droplet through a freely suspended liquid membrane. We investigate two kinds of liquid membranes: a grounded membrane and a pre-charged membrane. The falling of a droplet (about 40 μL) can generate a peak power of 137.4 nW by passing through a pre-charged membrane. Moreover, this membrane electrode can also remove and collect electrostatic charges from solid objects, indicating a permeable sensor or charge filter for electronic applications. The liquid–liquid triboelectric nanogenerator can harvest mechanical energy without changing the object motion and it can work for many targets, including raindrops, irrigation currents, microfluidics, and tiny particles. Triboelectric nanogenerators harvest energy by contacting two solids or a liquid and a solid. Here the authors use a conductive liquid membrane as a permeable electrode to demonstrate triboelectrification via liquid–liquid contact by passing liquid droplets through a liquid membrane to generate power.

218 citations


Journal ArticleDOI
21 Aug 2019-Nature
TL;DR: A method of droplet manipulation is described that uses electrical signals to induce the liquid to dewet, rather than wet, a hydrophilic conductive surface without the need for added layers, promising a simple and reliable microfluidic platform for a broad range of applications.
Abstract: The ability to manipulate droplets on a substrate using electric signals1—known as digital microfluidics—is used in optical2,3, biomedical4,5, thermal6 and electronic7 applications and has led to commercially available liquid lenses8 and diagnostics kits9,10. Such electrical actuation is mainly achieved by electrowetting, with droplets attracted towards and spreading on a conductive substrate in response to an applied voltage. To ensure strong and practical actuation, the substrate is covered with a dielectric layer and a hydrophobic topcoat for electrowetting-on-dielectric (EWOD)11-13; this increases the actuation voltage (to about 100 volts) and can compromise reliability owing to dielectric breakdown14, electric charging15 and biofouling16. Here we demonstrate droplet manipulation that uses electrical signals to induce the liquid to dewet, rather than wet, a hydrophilic conductive substrate without the need for added layers. In this electrodewetting mechanism, which is phenomenologically opposite to electrowetting, the liquid–substrate interaction is not controlled directly by electric field but instead by field-induced attachment and detachment of ionic surfactants to the substrate. We show that this actuation mechanism can perform all the basic fluidic operations of digital microfluidics using water on doped silicon wafers in air, with only ±2.5 volts of driving voltage, a few microamperes of current and about 0.015 times the critical micelle concentration of an ionic surfactant. The system can also handle common buffers and organic solvents, promising a simple and reliable microfluidic platform for a broad range of applications. A method of droplet manipulation is described that uses electrical signals to induce the liquid to dewet, rather than wet, a hydrophilic conductive surface.

141 citations



Journal ArticleDOI
TL;DR: The review provides researchers and engineers with an extensive and updated understanding of the principles and applications of flexible microfluidics.
Abstract: Miniaturization has been the driving force of scientific and technological advances over recent decades. Recently, flexibility has gained significant interest, particularly in miniaturization approaches for biomedical devices, wearable sensing technologies, and drug delivery. Flexible microfluidics is an emerging area that impacts upon a range of research areas including chemistry, electronics, biology, and medicine. Various materials with flexibility and stretchability have been used in flexible microfluidics. Flexible microchannels allow for strong fluid-structure interactions. Thus, they behave in a different way from rigid microchannels with fluid passing through them. This unique behaviour introduces new characteristics that can be deployed in microfluidic applications and functions such as valving, pumping, mixing, and separation. To date, a specialised review of flexible microfluidics that considers both the fundamentals and applications is missing in the literature. This review aims to provide a comprehensive summary including: (i) Materials used for fabrication of flexible microfluidics, (ii) basics and roles of flexibility on microfluidic functions, (iii) applications of flexible microfluidics in wearable electronics and biology, and (iv) future perspectives of flexible microfluidics. The review provides researchers and engineers with an extensive and updated understanding of the principles and applications of flexible microfluidics.

118 citations


Journal ArticleDOI
TL;DR: This review will summarize the advances of microfluidics for single-cell manipulation and analysis from the aspects of methods and applications, and outlook the trend ofmicrofluidic single- cell analysis.
Abstract: In a forest of a hundred thousand trees, no two leaves are alike. Similarly, no two cells in a genetically identical group are the same. This heterogeneity at the single-cell level has been recognized to be vital for the correct interpretation of diagnostic and therapeutic results of diseases, but has been masked for a long time by studying average responses from a population. To comprehensively understand cell heterogeneity, diverse manipulation and comprehensive analysis of cells at the single-cell level are demanded. However, using traditional biological tools, such as petri-dishes and well-plates, is technically challengeable for manipulating and analyzing single-cells with small size and low concentration of target biomolecules. With the development of microfluidics, which is a technology of manipulating and controlling fluids in the range of micro- to pico-liters in networks of channels with dimensions from tens to hundreds of microns, single-cell study has been blooming for almost two decades. Comparing to conventional petri-dish or well-plate experiments, microfluidic single-cell analysis offers advantages of higher throughput, smaller sample volume, automatic sample processing, and lower contamination risk, etc., which made microfluidics an ideal technology for conducting statically meaningful single-cell research. In this review, we will summarize the advances of microfluidics for single-cell manipulation and analysis from the aspects of methods and applications. First, various methods, such as hydrodynamic and electrical approaches, for microfluidic single-cell manipulation will be summarized. Second, single-cell analysis ranging from cellular to genetic level by using microfluidic technology is summarized. Last, we will also discuss the advantages and disadvantages of various microfluidic methods for single-cell manipulation, and then outlook the trend of microfluidic single-cell analysis.

116 citations



Journal ArticleDOI
TL;DR: The survey shows that these subdisciplines of DNA nanotechnology are growing ever closer together and suggests that this integration is essential in order to initiate the next phase of development.
Abstract: In the past 35 years, DNA nanotechnology has grown to a highly innovative and vibrant field of research at the interface of chemistry, materials science, biotechnology, and nanotechnology. Herein, a short summary of the state of research in various subdisciplines of DNA nanotechnology, ranging from pure "structural DNA nanotechnology" over protein-DNA assemblies, nanoparticle-based DNA materials, and DNA polymers to DNA surface technology is given. The survey shows that these subdisciplines are growing ever closer together and suggests that this integration is essential in order to initiate the next phase of development. With the increasing implementation of machine-based approaches in microfluidics, robotics, and data-driven science, DNA-material systems will emerge that could be suitable for applications in sensor technology, photonics, as interfaces between technical systems and living organisms, or for biomimetic fabrication processes.

110 citations


Journal ArticleDOI
Dan Gao1, Dan Gao2, Feng Jin2, Min Zhou1, Yuyang Jiang1 
28 Jan 2019-Analyst
TL;DR: This review highlights the advances in this field during the past three years in the following three aspects: microfluidic single cell manipulation based on microwells, micropatterns, droplets, traps and flow cytometric methods; detection methods based on fluorescence, mass spectrometry, electrochemical, and polymerase chain reaction-based analysis; and applications in the fields of small molecule detection, protein analysis, multidrug resistance analysis, and single cell sequencing with droplet microflu
Abstract: Single cell analysis has become of great interest with unprecedented capabilities for the systematic investigation of cell-to-cell variation in large populations. Rapid and multi-parametric analysis of intercellular biomolecules at the single-cell level is imperative for the improvement of early disease diagnosis and personalized medicine. However, the small size of cells and the low concentration levels of target biomolecules are critical challenges for single cell analysis. In recent years, microfluidic platforms capable of handling small-volume fluid have been demonstrated to be powerful tools for single cell analysis. In addition, microfluidic techniques allow for precise control of the localized microenvironment, which yield more accurate outcomes. Many different microfluidic techniques have been greatly improved for highly efficient single-cell manipulation and highly sensitive detection over the past few decades. To date, microfluidics-based single cell analysis has become the hot research topic in this field. In this review, we particularly highlight the advances in this field during the past three years in the following three aspects: (1) microfluidic single cell manipulation based on microwells, micropatterns, droplets, traps and flow cytometric methods; (2) detection methods based on fluorescence, mass spectrometry, electrochemical, and polymerase chain reaction-based analysis; (3) applications in the fields of small molecule detection, protein analysis, multidrug resistance analysis, and single cell sequencing with droplet microfluidics. We also discuss future research opportunities by focusing on key performances of throughput, multiparametric target detection and data processing.

103 citations


Journal ArticleDOI
TL;DR: An all-aqueous-phase microfluidics is presented to achieve oil-free emulsification of cell-laden microcapsules and 3D cell culture, and core-shell micro Capsules with controllable structures can be stably and continuously generated.
Abstract: Cell-laden hydrogel microcarriers are widely used in diverse biomedical applications like three-dimensional (3D) cell culture, cellular therapy, and tissue engineering, where microcarriers were generally produced by oil, which is the common but not optimal choice, as oil may cause cytotoxicity or protein denaturation. Here, an all-aqueous-phase microfluidics is presented to achieve oil-free emulsification of cell-laden microcapsules and 3D cell culture. Aqueous solutions with different concentration gradients are used as an immiscible continuous phase and a dispersed phase, and oscillation from a solenoid valve facilitates the formation of microcapsules at the water-water interface. By adjusting aqueous-phase flow rates and oscillating frequencies, core-shell microcapsules with controllable structures can be stably and continuously generated. In further 3D cell culture, encapsulated cells maintained good viabilities and aggregated together. These features show that the oil-free microfluidic method may have broad prospects in many biomedical applications.

92 citations


Journal ArticleDOI
TL;DR: The latest advances in microfluidics-based biomaterials and biodevices are reviewed, highlighting some burgeoning areas such as functional biomaterialS, cell manipulations, and flexible biodesvices that unify at the ultimate goals in human healthcare.
Abstract: The rapid development of microfluidics technology has promoted new innovations in materials science, particularly by interacting with biological systems, based on precise manipulation of fluids and cells within microscale confinements. This article reviews the latest advances in microfluidics-based biomaterials and biodevices, highlighting some burgeoning areas such as functional biomaterials, cell manipulations, and flexible biodevices. These areas are interconnected not only in their basic principles, in that they all employ microfluidics to control the makeup and morphology of materials, but also unify at the ultimate goals in human healthcare. The challenges and future development trends in biological application are also presented.

90 citations


Journal ArticleDOI
TL;DR: This review introduces the basic theory of DEP, its advantages compared with other separation methods, and its applications in recent years, in particular, focusing on the different electrode types integrated into microfluidic chips, fabrication techniques, and operation principles.
Abstract: Dielectric particles in a non-uniform electric field are subject to a force caused by a phenomenon called dielectrophoresis (DEP). DEP is a commonly used technique in microfluidics for particle or cell separation. In comparison with other separation methods, DEP has the unique advantage of being label-free, fast, and accurate. It has been widely applied in microfluidics for bio-molecular diagnostics and medical and polymer research. This review introduces the basic theory of DEP, its advantages compared with other separation methods, and its applications in recent years, in particular, focusing on the different electrode types integrated into microfluidic chips, fabrication techniques, and operation principles.

Journal ArticleDOI
TL;DR: An overview of the microfabrication techniques is given, especially for biomedical applications, as well as a synopsis of some design considerations regarding microfluidic devices.
Abstract: Since the first microfluidic device was developed more than three decades ago, microfluidics is seen as a technology that exhibits unique features to provide a significant change in the way that modern biology is performed. Blood and blood cells are recognized as important biomarkers of many diseases. Taken advantage of microfluidics assets, changes on blood cell physicochemical properties can be used for fast and accurate clinical diagnosis. In this review, an overview of the microfabrication techniques is given, especially for biomedical applications, as well as a synopsis of some design considerations regarding microfluidic devices. The blood cells separation and sorting techniques were also reviewed, highlighting the main achievements and breakthroughs in the last decades.

Journal ArticleDOI
TL;DR: The current contribution considers the intervening eight years, and assess the contributions that droplet-based microfluidics has made to experimental science in its broadest sense.

Journal ArticleDOI
TL;DR: A board definition of the biosensor or biosensing system that incorporates any method coupling these two key elements, and ultimately achieving "sample-in-answer-out" is provided.
Abstract: Biosensors are analytical devices or systems used to detect a specific target by converting and amplifying a biomolecular recognition event to a dateable semi-quantitative or quantitative signal. Biosensors are powerful analytical tools for the detection of biological or chemical molecules.1 In general, a biosensor consists of biological recognition and signal output elements. There are some definitions insist that the recognition element be physically adjacent to the signal output element. We appreciate this definition, but here we provide a board definition of the biosensor or biosensing system that incorporates any method coupling these two key elements, and ultimately achieving "sample-in-answer-out".

Journal ArticleDOI
TL;DR: Work that has the ability to de-risk the translation of liposomes from bench to the clinic is presented, demonstrating that FRR is a key factor influencing liposome size, protein loading and release profiles.

Journal ArticleDOI
TL;DR: The focus of this review is upon the cross‐stream nonlinear electrokinetic motions of particles in the linear electroosmotic flow of fluids, which enable the diverse control of particle transport in microchannels via the wall‐induced electrical lift and/or the insulating structure‐induced dielectrophoretic force.
Abstract: Microfluidic devices have been extensively used to achieve precise transport and placement of a variety of particles for numerous applications. A range of force fields have thus far been demonstrated to control the motion of particles in microchannels. Among them, electric field-driven particle manipulation may be the most popular and versatile technique because of its general applicability and adaptability as well as the ease of operation and integration into lab-on-a-chip systems. This article is aimed to review the recent advances in direct current (DC) (and as well DC-biased alternating current) electrokinetic manipulation of particles for microfluidic applications. The electric voltages are applied through electrodes that are positioned into the distant channel-end reservoirs for a concurrent transport of the suspending fluid and manipulation of the suspended particles. The focus of this review is upon the cross-stream nonlinear electrokinetic motions of particles in the linear electroosmotic flow of fluids, which enable the diverse control of particle transport in microchannels via the wall-induced electrical lift and/or the insulating structure-induced dielectrophoretic force.

Journal ArticleDOI
TL;DR: A new superhydrophobic shape memory adhesive surface that can solve the problem of no-loss and selective capture/release of different microdroplets and would be a powerful platform for microfluidics systems, complex droplet transportation, biological analysis, and so on.
Abstract: Controllable manipulation of microdroplets is significant for the microfluidics, biomedical areas, microreactors, and so on; however, until now, reports about no-loss and selective capture/release of different microdroplets are still rare. Herein, we report a new superhydrophobic shape memory adhesive surface that can solve this problem. The surface is prepared by sticking a pillar-structured superhydrophobic polyurethane layer onto a shape memory polyurethane-cellulose nanofiber (PU-CNF) layer. Because of the good shape memory performance of the PU-CNF layer, the obtained surface can memorize and display various microstructure arrangements during the stretching/releasing process. Meanwhile, multiple superhydrophobic adhesive states from low-adhesive rolling performance to high-adhesive pinning performance can be observed on the surface, and all these adhesive states can be reversibly controlled between each other. Based on the smart shape memory ability in surface adhesion, not only traditional in situ capture/release of one microdroplet but also selective capture and release of different microdroplets can be realized. This work reports a new superhydrophobic shape memory adhesive surface; it is envisioned that this smart surface would be a powerful platform for microfluidics systems, complex droplet transportation, biological analysis, and so on.

Journal ArticleDOI
TL;DR: This Perspective highlights fundamentals of open microfluidic capillary systems including unique advantages, design considerations, fabrication methods, and analytical considerations for flow; device features that can be combined to create a "toolbox" for fluid manipulation; and applications in biology, diagnostics, chemistry, sensing, and biphasic applications.
Abstract: Open microfluidic capillary systems are a rapidly evolving branch of microfluidics where fluids are manipulated by capillary forces in channels lacking physical walls on all sides. Typical channel ...

Journal ArticleDOI
TL;DR: In this paper, the authors used a direct ink writing (DIW) 3D printer to dispense a fast-curing flexible silicone resin on various substrates to form microchannels with tunable dimensions.
Abstract: This paper describes a simple method to apply 3D printing to fabricate microfluidic devices integrated with fluid handling and functional components. We used a direct ink writing (DIW) 3D printer to dispense a fast-curing flexible silicone resin on various substrates to form microchannels. The dispensed silicone was interfaced with another flat substrate to form microchannels with tunable dimensions. Using this method, we fabricated channels with dimensions as small as 32 μm in width and 30 μm height. We fabricated basic microfluidic modalities (e.g. straight and branched channels, mixers, chambers and droplet generators) as well as functional modalities (e.g. valves, variable flow resistors and gradient generators) on an optically transparent substrate. The method can be readily extended to fabricate microchannels on a diverse range of functional substrates. We showcased this capability by fabricating microchannels on an unmodified printed-circuit board (PCB) to form the interface between the fluid and the electric circuits, and microporous membranes to perform air-liquid human keratinocyte cell culture. Our approach has enabled rapid prototyping of microfluidic devices integrated with functional components required for lab-on-a-chip applications, complementing current approaches in 3D printed microfluidics that are restricted in attainable dimensions and available materials.

Journal ArticleDOI
TL;DR: A facile and straightforward flow synthesis strategy to control zinc oxide (ZnO) of different shapes on a few seconds time scale, based on the 1.5-run spiral-shaped microfluidic reactor, and the structure-dependent efficacy is observed, where higher surface area ZnO structures generally behave better performance.

Journal ArticleDOI
11 Dec 2019
TL;DR: An updated overview of the state of the art for passive label-free microparticle separation, with emphasis on performance and operational conditions is provided and the newly emerging approach based on shear-induced diffusion is highlighted.
Abstract: Massive growth of the microfluidics field has triggered numerous advances in focusing, separating, ordering, concentrating, and mixing of microparticles. Microfluidic systems capable of performing these functions are rapidly finding applications in industrial, environmental, and biomedical fields. Passive and label-free methods are one of the major categories of such systems that have received enormous attention owing to device operational simplicity and low costs. With new platforms continuously being proposed, our aim here is to provide an updated overview of the state of the art for passive label-free microparticle separation, with emphasis on performance and operational conditions. In addition to the now common separation approaches using Newtonian flows, such as deterministic lateral displacement, pinched flow fractionation, cross-flow filtration, hydrodynamic filtration, and inertial microfluidics, we also discuss separation approaches using non-Newtonian, viscoelastic flow. We then highlight the newly emerging approach based on shear-induced diffusion, which enables direct processing of complex samples such as untreated whole blood. Finally, we hope that an improved understanding of label-free passive sorting approaches can lead to sophisticated and useful platforms toward automation in industrial, environmental, and biomedical fields.

Journal ArticleDOI
TL;DR: In this paper, a general overview of the advantages, drawbacks, and gaps as well as remaining challenges and future trends of coupling microfluidics and electrochemical cells is presented, where special attention is given to the manufacturing and scale-up of the integrated devices and all those aspects that can push on the development of true lab-on-a-chip platforms for reaching the industrial domain and actual commercialization.

Journal ArticleDOI
TL;DR: A platform for the stable analysis of microfluidic droplet samples by nESI-MS, an attractive approach for droplet analysis, that allows rapid, label-free, information-rich analysis with high mass sensitivity and resistance to matrix effects is described.
Abstract: Droplet microfluidics enables high-throughput manipulation of fL−μL volume samples. Methods implemented for the chemical analysis of microfluidic droplets have been limited in scope, leaving some a...

Journal ArticleDOI
TL;DR: In this review, the bibliography is explored by looking for these new systems that, combining microfluidics and hydrogels, substantially contribute to the state of the art.
Abstract: Microfluidics is a very useful and promising technology that allowed engineering a huge variety of developments in several fields, such as biology, biomedical engineering, biotechnology, biochemistry, medicine and tissue engineering, among others. Moreover, when microfluidic is combined with hydrogel, the possibilities seem to be limitless. However, it is not found in the bibliography any report that shows the wide range of developments and application fields of this combination. In this review, the bibliography is explored by looking for these new systems that, combining microfluidics and hydrogels, substantially contribute to the state of the art. Seven large application fields are identified -from 649 papers reviewed-: 1) cell culture (out of the scope of this review), 2) biosensors, 3) gradient generator microdevices (GGMD), 4) active elements of hydrogel embedded into microfluidic devices, 5) separation devices, 6) models and 7) other uses. Most of these fields are presented and discussed in detail, the great benefits of the combination are highlighted and perspectives on future directions are exposed.

Journal ArticleDOI
TL;DR: This method enables the manufacturing of a fully-functional microfluidic device in a few hours, without using any projection masks, dangerous chemicals, and additional expensive tools, e.g., a mask writer or bonding machine.
Abstract: Conventional manufacturing of glass microfluidic devices is a complex, multi-step process that involves a combination of different fabrication techniques, typically photolithography, chemical/dry etching and thermal/anodic bonding. As a result, the process is time-consuming and expensive, in particular when developing microfluidic prototypes or even manufacturing them in low quantity. This report describes a fabrication technique in which a picosecond pulsed laser system is the only tool required to manufacture a microfluidic device from transparent glass substrates. The laser system is used for the generation of microfluidic patterns directly on glass, the drilling of inlet/outlet ports in glass covers, and the bonding of two glass plates together in order to enclose the laser-generated patterns from the top. This method enables the manufacturing of a fully-functional microfluidic device in a few hours, without using any projection masks, dangerous chemicals, and additional expensive tools, e.g., a mask writer or bonding machine. The method allows the fabrication of various types of microfluidic devices, e.g., Hele-Shaw cells and microfluidics comprising complex patterns resembling up-scaled cross-sections of realistic rock samples, suitable for the investigation of CO2 storage, water remediation and hydrocarbon recovery processes. The method also provides a route for embedding small 3D objects inside these devices.

Journal ArticleDOI
Yunru Yu1, Jiahui Guo1, Lingyu Sun1, Xiaoxuan Zhang1, Yuanjin Zhao1 
19 Jun 2019
TL;DR: By embedding them into stretchable films, the simple paradigm of a flexible device shows great conductive performance in tensile tests and even motion cycles, which could be explored as a promising candidate in stretchable sensors, flexible electronics, and electronic skins.
Abstract: Inspired by helical or spiral veins, which endow plants with excellent flexibility and elasticity to withstand storms, we present novel hollow microsprings with ionic liquid encapsulation for flexible and stretchable electronics. The microsprings were generated by using a coaxial capillary microfluidic device to consecutively spin poly(vinylidene fluoride) (PVDF) presolution and an ionic liquid, which formed laminar flows in the coaxial injection microfluidic channels. The fast phase inversion of PVDF helps to form the core-shell structure of a microfiber and guarantees the in situ encapsulation of ionic liquid. The hybrid microfiber can then spiral and be further solidified to maintain the helical structure with increasing flow rates of the injection fluids. Because of the feasible and precise control of the injection fluids during the microfluidic spinning, the resultant microsprings have controlled core-shell structures, helical pitches, and corresponding electromechanical properties. By further embedding them into stretchable films, the simple paradigm of a flexible device shows great conductive performance in tensile tests and even motion cycles, which could be explored as a promising candidate in stretchable sensors, flexible electronics, and electronic skins.

Journal ArticleDOI
TL;DR: A SERS-based gradient droplet system will be of significant utility in simultaneously monitoring chemical and biological reactions for various concentrations of a reagent in this two-phase liquid/liquid segmented flow regime.
Abstract: In the last two decades, microfluidic technology has emerged as a highly efficient tool for the study of various chemical and biological reactions. Recently, we reported that high-throughput detection of various concentrations of a reagent is possible using a continuous gradient microfluidic channel combined with a surface-enhanced Raman scattering (SERS) detection platform. In this continuous flow regime, however, the deposition of nanoparticle aggregates on channel surfaces induces the “memory effect,” affecting both sensitivity and reproducibility. To resolve this problem, a SERS-based gradient droplet system was developed. Herein, the serial dilution of a reagent was achieved in a stepwise manner using microfluidic concentration gradient generators. Then various concentrations of a reagent generated in different channels were simultaneously trapped into the tiny volume of droplets by injecting an oil mixture into the channel. Compared to the single-phase regime, this two-phase liquid/liquid segmented flow regime allows minimization of resident time distributions of reagents through localization of reagents in encapsulated droplets. Consequently, the sample stacking problem could be solved using this system because it greatly reduces the memory effect. We believe that this SERS-based gradient droplet system will be of significant utility in simultaneously monitoring chemical and biological reactions for various concentrations of a reagent.

Journal ArticleDOI
TL;DR: A facile Eutectic Galium-Indium (EGaln) liquid-based microfluidic high-sensitivity, skin-mountable, and ultra-soft stretchable sensor is developed that achieves an outstanding effect on elastomer-encapsulated strain gauge, which displays an approximately linear behavior with a gauge factor (GF).
Abstract: Room-temperature liquid metal has been widely used in flexible and stretchable sensors, focusing on embedding liquid metal in microchannels, liquid metal microdroplets formation, captive sensors, and liquid metal nanoparticles, etc. In this paper, a facile Eutectic Galium-Indium (EGaln) liquid-based microfluidic high-sensitivity, skin-mountable, and ultra-soft stretchable sensor is developed. It comprises Ecoflex microfluidic assembly filled with EGaln, which serves as the working fluid of the stretchable sensor. The lithography method is applied to achieve microfluidic channel. The microfluidic channel is optimized by using topology method and finite element analysis, making this device with high conformability and high stretchability. This method achieved an outstanding effect on elastomer-encapsulated strain gauge, which displays an approximately linear behavior with a gauge factor (GF). The GF could reach as high as 4.95 when the strain ultimately reached 550%. Applications of detection of the joints, fingers, and wrists has been conducted and showed excellent results. This work can further facilitate the exploration and potential realization of a functional liquid-state device technology with superior mechanical flexibility and conformability.

Journal ArticleDOI
TL;DR: The ID2M platform has been validated as a robust on-demand screening system by sorting fluorescein droplets of different concentration with an efficiency of ∼96% and has the potential to be used for screening different conditions on-chip and for applications like directed evolution.
Abstract: Droplet microfluidics is a technique that has the ability to compartmentalize reactions in sub nano- (or pico-) liter volumes that can potentially enable millions of distinct biological assays to be performed on individual cells. In a typical droplet microfluidic system, droplets are manipulated by pressure-based flows. This has limited the fluidic operations that can be performed in these devices. Digital microfluidics is an alternative microfluidic paradigm with precise control and manipulation over individual droplets. Here, we implement an integrated droplet-digital microfluidic (which we call 'ID2M') system in which common fluidic operations (i.e. droplet generation, cell encapsulation, droplet merging and mixing, droplet trapping and incubation, and droplet sorting) can be performed. With the addition of electrodes, we have been able to create droplets on-demand, tune their volumes on-demand, and merge and mix several droplets to produce a dilution series. Moreover, this device can trap and incubate droplets for 24 h that can consequently be sorted and analyzed in multiple n-ary channels (as opposed to typical binary channels). The ID2M platform has been validated as a robust on-demand screening system by sorting fluorescein droplets of different concentration with an efficiency of ∼96%. The utility of the new system is further demonstrated by culturing and sorting tolerant yeast mutants and wild-type yeast cells in ionic liquid based on their growth profiles. This new platform for both droplet and digital microfluidics has the potential to be used for screening different conditions on-chip and for applications like directed evolution.

Journal ArticleDOI
Bo Xu1, Chongyu Zhu1, Lang Qin1, Jia Wei1, Yanlei Yu1 
01 Jun 2019-Small
TL;DR: An alternative strategy is presented for light-directed liquid manipulation in flexible bilayer microtubes, which are composed of a commercially available supporting layer and the photodeformable layer of a newly designed azobenzene-containing linear liquid crystal copolymer.
Abstract: Flexible microfluidic systems have potential in wearable and implantable medical applications. Directional liquid transportation in these systems typically requires mechanical pumps, gas tanks, and magnetic actuators. Herein, an alternative strategy is presented for light-directed liquid manipulation in flexible bilayer microtubes, which are composed of a commercially available supporting layer and the photodeformable layer of a newly designed azobenzene-containing linear liquid crystal copolymer. Upon moderate visible light irradiation, various liquid slugs confined in the flexible microtubes are driven in the preset direction over a long distance due to photodeformation-induced asymmetric capillary forces. Several light-driven prototypes of parallel array, closed-loop channel, and multiple micropump are established by the flexible bilayer microtubes to achieve liquid manipulation. Furthermore, an example of a wearable device attached to a finger for light-directed liquid motion is demonstrated in different gestures. These unique photocontrollable flexible microtubes offer a novel concept of wearable microfluidics.