A high-throughput microfluidic nanoimmunoassay for detecting anti-SARS-CoV-2 antibodies in serum or ultralow-volume blood samples

Novel technologies are needed to facilitate large-scale detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibodies in human blood samples. Such technologies are essential to support seroprevalence studies and vaccine clinical trials, and to monitor quality and duration of immunity. We developed a microfluidic nanoimmunoassay (NIA) for the detection of anti-SARS-CoV-2 IgG antibodies in 1,024 samples per device. The method achieved a specificity of 100% and a sensitivity of 98% based on the analysis of 289 human serum samples. To eliminate the need for venipuncture, we developed low-cost, ultralow-volume whole blood sampling methods based on two commercial devices and repurposed a blood glucose test strip. The glucose test strip permits the collection, shipment, and analysis of 0.6 μL of whole blood easily obtainable from a simple finger prick. The NIA platform achieves high throughput, high sensitivity, and specificity based on the analysis of 289 human serum samples, and negligible reagent consumption. We furthermore demonstrate the possibility to combine NIA with decentralized and simple approaches to blood sample collection. We expect this technology to be applicable to current and future SARS-CoV-2 related serological studies and to protein biomarker analysis in general.

Triple Emulsion-Based Rapid Microfluidic Production of Core-Shell Hydrogel Microspheres for Programmable Biomolecular Conjugation

We report a simple and rapid microfluidic approach to produce core-shell hydrogel microspheres in a single step. We exploit triple emulsion drops with sacrificial oil layers that separate two prepolymer phases, forming poly(ethylene glycol)-based core-shell microspheres via photopolymerization followed by spontaneous removal of the oil layer. Our technique enables the production of monodisperse core-shell microspheres with varying dimensions of each compartment by independently and precisely controlled flow rates. This leads to stable and uniform incorporation of functional moieties in the core compartment with negligible cross-contamination into the shell layer. Selective conjugation of biomolecules is enabled through a rapid bioorthogonal reaction with functional groups in the core compartment with minimal non-specific adsorption. Finally, in-depth protein conjugation kinetics studies using microspheres with varying shell porosities highlight the capability to provide tunable size-selective diffusion barriers by simple tuning of prepolymer compositions for the shell layer. Combined, these results illustrate a significant step forward for programmable high-throughput fabrication of multifunctional hydrogel microspheres, which possess substantial potential in a large array of biomedical and biochemical applications.

Tumor spheroid-on-a-chip: a standardized microfluidic culture platform for investigating tumor angiogenesis

The field of microfluidics-based three-dimensional (3D) cell culture system is rapidly progressing from academic proof-of-concept studies to valid solutions to real-world problems. Polydimethylsiloxane (PDMS)-based platform has been widely adopted as in vitro platforms for mimicking tumor microenvironment. However, PDMS has not been welcomed as a standardized commercial application for preclinical screening due to inherent material limitations that make it difficult to scale-up production. Here, we present an injection-molded plastic array 3D spheroid culture platform (Sphero-IMPACT). The platform is made of polystyrene (PS) in a standardized 96-well plate format with a user-friendly interface. This interface describes a simpler design that incorporates a tapered hole in the center of the rail to pattern a large spheroid with 3D extracellular matrix and various cell types. This hole is designed to accommodate standard pipette tip for automated system. The platform that mediate open microfluidics allows implement spontaneous fluid patterning with high repeatability from the end user. To demonstrate versatile use of the platform, we developed 3D perfusable blood vessel network and tumor spheroid assays. In addition, we established a tumor spheroid induced angiogenesis model that can be applicable for drug screening. Sphero-IMPACT has the potential to provide a robust and reproducible in vitro assay related to vascularized cancer research. This easy-to-use, ready-to-use platform can be translated into an enhanced preclinical model that faithfully reflects the complex tumor microenvironment.

A rapid and low-cost fabrication and integration scheme to render 3D microfluidic architectures for wearable biofluid sampling, manipulation, and sensing

The large-scale deployment of wearable bioanalytical devices for general population longitudinal monitoring necessitates rapid and high throughput manufacturing-amenable fabrication schemes that render disposable, low-cost, and mechanically flexible microfluidic modules capable of performing a variety of bioanalytical operations within a compact footprint. The spatial constraints of previously reported wearable bioanalytical devices (with microfluidic operations confined to 2D), their lack of biofluid manipulation capability, and the complex and low-throughput nature of their fabrication process inherently limit the diversity and frequency of end-point assessments and prevent their deployment at large scale. Here, we devise a simple, scalable, and low-cost "CAD-to-3D Device" fabrication and integration scheme, which renders 3D and complex microfluidic architectures capable of performing biofluid sampling, manipulation, and sensing. The devised scheme is based on laser-cutting of tape-based substrates, which can be programmed at the software-level to rapidly define microfluidic features such as a biofluid collection interface, microchannels, and VIAs (vertical interconnect access), followed by the vertical assembly of pre-patterned layers to realize the final device. To inform the utility of our fabrication scheme, we demonstrated three representative devices to perform sweat collection (with visualizable secretion profile), sample filtration, and simultaneous biofluid actuation and sensing (using a sandwiched-interface). Our devised scheme can be adapted for the fabrication and manufacturing of current and future wearable bioanalytical devices, which in turn will catalyze the large-scale production and deployment of such devices for general population health monitoring.

Reliable and reusable whole polypropylene plastic microfluidic devices for a rapid, low-cost antimicrobial susceptibility test

Using an antimicrobial susceptibility test (AST) as an example, this work demonstrates a practical method to fabricate microfluidic chips entirely from polypropylene (PP) and the benefits for potential commercial use. Primarily caused by the misuse and abuse of antibiotics, antimicrobial resistance (AMR) is a major threat to modern medicine. The AST is a promising technique to help with the optimal use of antibiotics for reducing AMR. However, current phenotypic ASTs suffer from long turnaround time, while genotypic ASTs suffer from low reliability, and both are unaffordable for routine use. New microfluidics based AST methods are rapid but still unreliable as well as costly due to the PDMS chip material. Herein, we demonstrate a convenient method to fabricate whole PP microfluidic chips with high resolution and fidelity. Unlike PDMS chips, the whole PP chips showed better reliability due to their inertness; they are solvent-compatible and can be conveniently reused and recycled, which largely decreases the cost, and are environmentally friendly. We specially designed 3D chambers that allow for quick cell loading without valving/liquid exchange; this new hydrodynamic design satisfies the shear stress requirement for on-chip bacterial culture, which, compared to reported designs for similar purposes, allows for a simpler, more rapid, and high-throughput operation. Our system allows for reliable tracking of individual cells and acquisition of AST results within 1-3 hours, which is among the group of fastest phenotypic methods. The PP chips are more reliable and affordable than PDMS chips, providing a practical solution to improve current culture-based AST and benefiting the fight against AMR through helping doctors prescribe effective, narrow-spectrum antibiotics; they will also be broadly useful for other applications wherein a reliable, solvent-resistant, anti-fouling, and affordable microfluidic chip is needed.

Emerging Analytical Techniques for Rapid Pathogen Identification and Susceptibility Testing

In the face of looming threats from multi-drug resistant microorganisms, there is a growing need for technologies that will enable rapid identification and drug susceptibility profiling of these pathogens in health care settings. In particular, recent progress in microfluidics and nucleic acid amplification is pushing the boundaries of timescale for diagnosing bacterial infections. With a diverse range of techniques and parallel developments in the field of analytical chemistry, an integrative perspective is needed to understand the significance of these developments. This review examines the scope of new developments in assay technologies grouped by key enabling domains of research. First, we examine recent development in nucleic acid amplification assays for rapid identification and drug susceptibility testing in bacterial infections. Next, we examine advances in microfluidics that facilitate acceleration of diagnostic assays via integration and scale. Lastly, recentdevelopments in biosensor technologies are reviewed. We conclude this review with perspectives on the use of emerging concepts to develop paradigm-changing assays.

A low-cost, non-invasive phase velocity and length meter and controller for multiphase lab-in-a-tube devices

Opportunities for accessible microfluidic device integration have sharply grown with the rise of readily available lab-in-a-tube strategies. Herein, we present a facile, non-invasive, plug-and-play phase velocity and length measuring strategy for rapid deployment onto tube-based microfluidic systems, enabling quick and accurate residence (reaction) time measurement and tuning. Our approach utilizes inexpensive off-the-shelf optical phase sensors and requires no prior knowledge of the fluid composition or physical properties. Compared to camera-based measurements in fluoropolymer tubing, the optical phase sensor-based technique shows mean absolute percentage errors of 1.3% for velocity and 3.3% for length. Utilizing the developed multiphase flow monitoring technique, we screen the accessible parameter space of gas-liquid segmented flows. To further demonstrate the functionality of this process monitoring strategy, we implement two feedback controllers to establish simultaneous setpoint control for phase velocity and length. Next, to showcase the effectiveness and versatility of the developed multiphase flow process controller, we apply it to systematic studies of the effect of liquid slug velocity (controlling precursor mixing timescale) on the colloidal synthesis of cesium lead tribromide nanocrystals. By varying the liquid slug velocity and maintaining constant precursor composition, liquid slug length, and residence time, we observe a bandgap tunability from 2.43 eV (510 nm) to 2.52 eV (494 nm).

A microfluidic based biosensor for rapid detection of Salmonella in food products

An impedance based microfluidic biosensor for simultaneous and rapid detection of Salmonella serotypes B and D in ready-to-eat (RTE) Turkey matrix has been presented. Detection of Salmonella at a concentration as low as 300 cells/ml with a total detection time of 1 hour has been achieved. The sensor has two sensing regions, with each formed from one interdigitated electrode array (IDE array) consisting of 50 finger pairs. First, Salmonella antibody type B and D were prepared and delivered to the sensor to functionalize each sensing region without causing any cross contamination. Then the RTE Turkey samples spiked with Salmonella types B and D were introduced into the biosensor via the antigen inlet. The response signal resulted from the binding between Salmonella and its specific antibody demonstrated the sensor’s ability to detect a single type of pathogen, and multiple pathogens simultaneously. In addition, the biosensor’s selectivity was tested using non-specific binding of E. coli O157 and E. coli DH5 Alpha while the IDE array was coated with the Salmonella antibody. The results also showed the sensor is capable to differentiate low concentration of live Salmonella cells from high concentration of dead Salmonella cells, and high concentration of E. coli cells. A detailed study on antibody immobilization that includes antibody concentration, antibody coating time (0.5–3 hours) and use of cross-linker has been performed. The study showed that Salmonella antibody to Salmonella antigen is not a factor of antibody concentration after electrodes were saturated with antibody, while the optimal coating time was found to be 1.5 hours, and the use of cross-linker has improved the signal response by 45–60%.

Recent advances in thread-based microfluidics for diagnostic applications

Over the past decades, researchers have been seeking attractive substrate materials to keep microfluidics improving to outbalance the drawbacks and issues. Cellulose substrates, including thread, paper and hydrogels are alternatives due to their distinct structural and mechanical properties for a number of applications. Thread have gained considerable attention and become promising powerful tool due to its advantages over paper-based systems thus finds numerous applications in the development of diagnostic systems, smart bandages and tissue engineering. To the best of our knowledge, no comprehensive review articles on the topic of thread-based microfluidics have been published and it is of significance for many scientific communities working on Microfluidics, Biosensors and Lab-on-Chip. This review gives an overview of the advances of thread-based microfluidic diagnostic devices in a variety of applications. It begins with an overall introduction of the fabrication followed by an in-depth review on the detection techniques in such devices and various applications with respect to effort and performance to date. A few perspective directions of thread-based microfluidics in its development are also discussed. Thread-based microfluidics are still at an early development stage and further improvements in terms of fabrication, analytical strategies, and function to become low-cost, low-volume and easy-to-use point-of-care (POC) diagnostic devices that can be adapted or commercialized for real world applications.

Accelerating bacterial growth detection and antimicrobial susceptibility assessment in integrated picoliter droplet platform

There remains an urgent need for rapid diagnostic methods that can evaluate antibiotic resistance for pathogenic bacteria in order to deliver targeted antibiotic treatments. Toward this end, we present a rapid and integrated single-cell biosensing platform, termed dropFAST, for bacterial growth detection and antimicrobial susceptibility assessment. DropFAST utilizes a rapid resazurin-based fluorescent growth assay coupled with stochastic confinement of bacteria in 20 pL droplets to detect signal from growing bacteria after 1h incubation, equivalent to 2-3 bacterial replications. Full integration of droplet generation, incubation, and detection into a single, uninterrupted stream also renders this platform uniquely suitable for in-line bacterial phenotypic growth assessment. To illustrate the concept of rapid digital antimicrobial susceptibility assessment, we employ the dropFAST platform to evaluate the antibacterial effect of gentamicin on E. coli growth.

Simple Approaches to Minimally-Instrumented, Microfluidic-Based Point-of-Care Nucleic Acid Amplification Tests

Designs and applications of microfluidics-based devices for molecular diagnostics (Nucleic Acid Amplification Tests, NAATs) in infectious disease testing are reviewed, with emphasis on minimally instrumented, point-of-care (POC) tests for resource-limited settings. Microfluidic cartridges ('chips') that combine solid-phase nucleic acid extraction; isothermal enzymatic nucleic acid amplification; pre-stored, paraffin-encapsulated lyophilized reagents; and real-time or endpoint optical detection are described. These chips can be used with a companion module for separating plasma from blood through a combined sedimentation-filtration effect. Three reporter types: Fluorescence, colorimetric dyes, and bioluminescence; and a new paradigm for end-point detection based on a diffusion-reaction column are compared. Multiplexing (parallel amplification and detection of multiple targets) is demonstrated. Low-cost detection and added functionality (data analysis, control, communication) can be realized using a cellphone platform with the chip. Some related and similar-purposed approaches by others are surveyed.

Self-powered integrated microfluidic point-of-care low-cost enabling (SIMPLE) chip

Portable, low-cost, and quantitative nucleic acid detection is desirable for point-of-care diagnostics; however, current polymerase chain reaction testing often requires time-consuming multiple steps and costly equipment. We report an integrated microfluidic diagnostic device capable of on-site quantitative nucleic acid detection directly from the blood without separate sample preparation steps. First, we prepatterned the amplification initiator [magnesium acetate (MgOAc)] on the chip to enable digital nucleic acid amplification. Second, a simplified sample preparation step is demonstrated, where the plasma is separated autonomously into 224 microwells (100 nl per well) without any hemolysis. Furthermore, self-powered microfluidic pumping without any external pumps, controllers, or power sources is accomplished by an integrated vacuum battery on the chip. This simple chip allows rapid quantitative digital nucleic acid detection directly from human blood samples (10 to 10⁵ copies of methicillin-resistant Staphylococcus aureus DNA per microliter, ~30 min, via isothermal recombinase polymerase amplification). These autonomous, portable, lab-on-chip technologies provide promising foundations for future low-cost molecular diagnostic assays.

Challenges and opportunities for translating medical microdevices: insights from the programmable bio-nano-chip

This perspective highlights the major challenges for the bioanalytical community, in particular the area of lab-on-a-chip sensors, as they relate to point-of-care diagnostics. There is a strong need for general-purpose and universal biosensing platforms that can perform multiplexed and multiclass assays on real-world clinical samples. However, the adoption of novel lab-on-a-chip/microfluidic devices has been slow as several key challenges remain for the translation of these new devices to clinical practice. A pipeline of promising medical microdevice technologies will be made possible by addressing the challenges of integration, failure to compete with cost and performance of existing technologies, requisite for new content, and regulatory approval and clinical adoption.

Integrated microfluidic system for rapid detection of influenza H1N1 virus using a sandwich-based aptamer assay

The rapid spread of influenza-associated H1N1 viruses has caused serious concern in recent years. Therefore, there is an urgent need for the development of automatic, point-of-care devices for rapid diagnosis of the influenza virus. Conventional approaches suffer from several critical issues; notably, they are time-consuming, labor-intensive, and are characterized by relatively low sensitivity. In this work, we present a new approach for fluorescence-based detection of the influenza A H1N1 virus using a sandwich-based aptamer assay that is automatically performed on an integrated microfluidic system. The entire detection process was shortened to 30min using this chip-based system which is much faster than the conventional viral culture method. The limit of detection was significantly improved to 0.032 hemagglutination unit due to the high affinity and high specificity of the H1N1-specific aptamers. The results showed that the two-aptamer microfluidic system had about 10(3) times higher sensitivity than the conventional serological diagnosis. It was demonstrated that the developed microfluidic system may play as a powerful tool in the detection of the H1N1 virus.

Low cost microfluidic device based on cotton threads for electroanalytical application

Microfluidic devices are an interesting alternative for performing analytical assays, due to the speed of analyses, reduced sample, reagent and solvent consumption and less waste generation. However, the high manufacturing costs still prevent the massive use of these devices worldwide. Here, we present the construction of a low cost microfluidic thread-based electroanalytical device (μTED), employing extremely cheap materials and a manufacturing process free of equipment. The microfluidic channels were built with cotton threads and the estimated cost per device was only $0.39. The flow of solutions (1.12 μL s(-1)) is generated spontaneously due to the capillary forces, eliminating the use of any pumping system. To demonstrate the analytical performance of the μTED, a simultaneous determination of acetaminophen (ACT) and diclofenac (DCF) was performed by multiple pulse amperometry (MPA). A linear dynamic range (LDR) of 10 to 320 μmol L(-1) for both species, a limit of detection (LOD) and a limit of quantitation (LOQ) of 1.4 and 4.7 μmol L(-1) and 2.5 and 8.3 μmol L(-1) for ACT and DCF, respectively, as well as an analytical frequency of 45 injections per hour were reached. Thus, the proposed device has shown potential to extend the use of microfluidic analytical devices, due to its simplicity, low cost and good analytical performance.

Multilevel fluidic flow control in a rotationally-driven polyester film microdevice created using laser print, cut and laminate

This paper presents a simple and cost-effective polyester toner microchip fabricated with laser print and cut lithography (PCL) to use with a battery-powered centrifugal platform for fluid handling. The combination of the PCL microfluidic disc and centrifugal platform: (1) allows parallel aliquoting of two different reagents of four different volumes ranging from nL to μL with an accuracy comparable to a piston-driven air pipette; (2) incorporates a reciprocating mixing unit driven by a surface-tension pump for further dilution of reagents, and (3) is amenable to larger scale integration of assay multiplexing (including all valves and mixers) without substantially increasing fabrication cost and time. For a proof of principle, a 10 min colorimetric assay for the quantitation of the protein level in the human blood plasma samples is demonstrated on chip with a limit of detection of ∼5 mg mL(-1) and coefficient of variance of ∼7%.

Mobile phone based electrochemiluminescence detection in paper-based microfluidic sensors

The development of simple, inexpensive paper-based sensors for medical diagnostics and other applications is now an important emerging area in the field of biosensors; however, the electronic instrument or reader used to interrogate such sensors adds significantly to the cost of the analysis. In this chapter we describe the design and construction of novel, low-cost disposable electrochemiluminescent (ECL) sensors based on screen printed carbon electrodes and paper-based microfluidics. Moreover, a method to interrogate these sensors using only a mobile phone is articulated. This is realized by exploiting the audio output of the device to achieve electrochemical control, while using the camera to detect the resulting light emitted during the ECL reaction. The combination of cell phone technology with low-cost paper microfluidic sensors dramatically reduces the cost of sensing and has the potential to enhance health-care outcomes by exploiting the functionality, connectivity, and close to worldwide penetration of mobile phone technology.

A siphonage flow and thread-based low-cost platform enables quantitative and sensitive assays

For pump-free, material abundant, portable, and easy-to-operate low-cost microfluidics, a siphonage flow microfluidic thread-based analytical device (S-μTAD) platform enabling quantitative and sensitive assays was designed. Renewable and continuous siphonage flow allowed replicate sampling and detection on one channel/device, obviating some possible inconsistencies among channels or devices. Y-shaped channels were fabricated with polyester cotton blend thread, due to its greater chemiluminescent sensitivity in comparison with that of cotton and polyester threads. S-μTAD sensors for glucose and uric acid were fabricated by using oxidase-immobilized cotton thread as the sample arm of the channels. The acceptable reproducibility and high sensitivity, demonstrated by the relative standard deviations of less than 5% in all cases and the detection limits of 4 × 10(-8) mol L(-1) for hydrogen peroxide, 1 × 10(-7) mol L(-1) for glucose, and 3 × 10(-6) mol L(-1) for uric acid, demonstrated the feasibility of the S-μTAD for quantitative assays. Good agreements between S-μTAD/sensor results and hospital results for blood glucose and uric acid assays indicated the capability of S-μTAD/sensors for the analysis of real samples. These findings proved the utility of siphonage for low-cost microfluidics and the suitability of our S-μTAD design for quantitative assays.

Opto-fluidics based microscopy and flow cytometry on a cell phone for blood analysis

Blood analysis is one of the most important clinical tests for medical diagnosis. Flow cytometry and optical microscopy are widely used techniques to perform blood analysis and therefore cost-effective translation of these technologies to resource limited settings is critical for various global health as well as telemedicine applications. In this chapter, we review our recent progress on the integration of imaging flow cytometry and fluorescent microscopy on a cell phone using compact, light-weight and cost-effective opto-fluidic attachments integrated onto the camera module of a smartphone. In our cell-phone based opto-fluidic imaging cytometry design, fluorescently labeled cells are delivered into the imaging area using a disposable micro-fluidic chip that is positioned above the existing camera unit of the cell phone. Battery powered light-emitting diodes (LEDs) are butt-coupled to the sides of this micro-fluidic chip without any lenses, which effectively acts as a multimode slab waveguide, where the excitation light is guided to excite the fluorescent targets within the micro-fluidic chip. Since the excitation light propagates perpendicular to the detection path, an inexpensive plastic absorption filter is able to reject most of the scattered light and create a decent dark-field background for fluorescent imaging. With this excitation geometry, the cell-phone camera can record fluorescent movies of the particles/cells as they are flowing through the microchannel. The digital frames of these fluorescent movies are then rapidly processed to quantify the count and the density of the labeled particles/cells within the solution under test. With a similar opto-fluidic design, we have recently demonstrated imaging and automated counting of stationary blood cells (e.g., labeled white blood cells or unlabeled red blood cells) loaded within a disposable cell counting chamber. We tested the performance of this cell-phone based imaging cytometry and blood analysis platform by measuring the density of red and white blood cells as well as hemoglobin concentration in human blood samples, which showed a good match to our measurement results obtained using a commercially available hematology analyzer. Such a cell-phone enabled opto-fluidics microscopy, flow cytometry, and blood analysis platform could be especially useful for various telemedicine applications in remote and resource-limited settings.

Mobile device for disease diagnosis and data tracking in resource-limited settings

Here we describe a low-cost mobile device that combines cell-phone and satellite communication technologies with fluid miniaturization techniques for performing all essential functions of enzyme-linked immunosorbent assay (ELISA). Disease-specific antigens are immobilized on the microfluidic surface, and disease specific antibodies are captured on the surface and visualized with silver-gold amplification. The diagnostic result is automatically determined by the device by measuring the absorbance through the silver-gold amplification in the microchannel. The results are displayed for the user and are synchronized to a remote patient record. The overall system aims to be portable, robust, low-power, and fully utilize the ability of mobile devices for bringing better health care to resource poor areas.

ElectroTaxis-on-a-Chip (ETC): an integrated quantitative high-throughput screening platform for electrical field-directed cell migration

Both endogenous and externally applied electrical stimulation can affect a wide range of cellular functions, including growth, migration, differentiation and division. Among those effects, the electrical field (EF)-directed cell migration, also known as electrotaxis, has received broad attention because it holds great potential in facilitating clinical wound healing. Electrotaxis experiment is conventionally conducted in centimetre-sized flow chambers built in Petri dishes. Despite the recent efforts to adapt microfluidics for electrotaxis studies, the current electrotaxis experimental setup is still cumbersome due to the needs of an external power supply and EF controlling/monitoring systems. There is also a lack of parallel experimental systems for high-throughput electrotaxis studies. In this paper, we present a first independently operable microfluidic platform for high-throughput electrotaxis studies, integrating all functional components for cell migration under EF stimulation (except microscopy) on a compact footprint (the same as a credit card), referred to as ElectroTaxis-on-a-Chip (ETC). Inspired by the R-2R resistor ladder topology in digital signal processing, we develop a systematic approach to design an infinitely expandable microfluidic generator of EF gradients for high-throughput and quantitative studies of EF-directed cell migration. Furthermore, a vacuum-assisted assembly method is utilized to allow direct and reversible attachment of our device to existing cell culture media on biological surfaces, which separates the cell culture and device preparation/fabrication steps. We have demonstrated that our ETC platform is capable of screening human cornea epithelial cell migration under the stimulation of an EF gradient spanning over three orders of magnitude. The screening results lead to the identification of the EF-sensitive range of that cell type, which can provide valuable guidance to the clinical application of EF-facilitated wound healing.

Rapid determination of cell mass and density using digitally controlled electric field in a microfluidic chip

The density of a single cell is a fundamental property of cells. Cells in the same cycle phase have similar volume, but the differences in their mass and density could elucidate each cell's physiological state. Here we report a novel technique to rapidly measure the density and mass of a single cell using an optically induced electrokinetics (OEK) microfluidic platform. Presently, single cellular mass and density measurement devices require a complicated fabrication process and their output is not scalable, i.e., it is extremely difficult to measure the mass and density of a large quantity of cells rapidly. The technique reported here operates on a principle combining sedimentation theory, computer vision, and microparticle manipulation techniques in an OEK microfluidic platform. We will show in this paper that this technique enables the measurement of single-cell volume, density, and mass rapidly and accurately in a repeatable manner. The technique is also scalable - it allows simultaneous measurement of volume, density, and mass of multiple cells. Essentially, a simple time-controlled projected light pattern is used to illuminate the selected area on the OEK microfluidic chip that contains cells to lift the cells to a particular height above the chip's surface. Then, the cells are allowed to "free fall" to the chip's surface, with competing buoyancy, gravitational, and fluidic drag forces acting on the cells. By using a computer vision algorithm to accurately track the motion of the cells and then relate the cells' motion trajectory to sedimentation theory, the volume, mass, and density of each cell can be rapidly determined. A theoretical model of micro-sized spheres settling towards an infinite plane in a microfluidic environment is first derived and validated experimentally using standard micropolystyrene beads to demonstrate the viability and accuracy of this new technique. Next, we show that the yeast cell volume, mass, and density could be rapidly determined using this technology, with results comparable to those using the existing method suspended microchannel resonator.

Self-powered Imbibing Microfluidic Pump by Liquid Encapsulation: SIMPLE

Reliable, autonomous, internally self-powered microfluidic pumps are in critical demand for rapid point-of-care (POC) devices, integrated molecular-diagnostic platforms, and drug delivery systems. Here we report on a Self-powered Imbibing Microfluidic Pump by Liquid Encapsulation (SIMPLE), which is disposable, autonomous, easy to use and fabricate, robust, and cost efficient, as a solution for self-powered microfluidic POC devices. The imbibition pump introduces the working liquid which is sucked into a porous material (paper) upon activation. The suction of the working liquid creates a reduced pressure in the analytical channel and induces the sequential sample flow into the microfluidic circuits. It requires no external power or control and can be simply activated by a fingertip press. The flow rate can be programmed by defining the shape of utilized porous material: by using three different paper shapes with circular section angles 20°, 40° and 60°, three different volume flow rates of 0.07 μL s(-1), 0.12 μL s(-1) and 0.17 μL s(-1) are demonstrated at 200 μm × 600 μm channel cross-section. We established the SIMPLE pumping of 17 μL of sample; however, the sample volume can be increased to several hundreds of μL. To demonstrate the design, fabrication, and characterization of SIMPLE, we used a simple, robust and cheap foil-laminating fabrication technique. The SIMPLE can be integrated into hydrophilic or hydrophobic materials-based microfluidic POC devices. Since it is also applicable to large-scale manufacturing processes, we anticipate that a new chapter of a cost effective, disposable, autonomous POC diagnostic chip is addressed with this technical innovation.

Low-cost experimentation for the study of droplet microfluidics

The continued growth of microfluidics into industry settings in areas such as point-of-care diagnostics and targeted therapeutics necessitates a workforce trained in microfluidic technologies and experimental methods. Laboratory courses for students at the university and high school levels will require cost-effective in-class demonstrations that instruct in chip design, fabrication, and experimentation at the microscale. We present a hand-operated pressure pumping system to form monodisperse picoliter to nanoliter droplet streams at low cost, and a series of exercises aimed at instructing in the specific art of droplet formation. Using this setup, the student is able to generate and observe the modes of droplet formation in flow-focusing devices, and the effect of device dimensions on the characteristics of formed droplets. Lastly, at ultra-low cost we demonstrate large plug formation in a T-junction using coffee stirrers as a master mold substitute. Our method reduces the cost of experimentation to enable intuitive instruction in droplet formation, with additional implications for creating droplets in the field or at point-of-care.

Preparation and validation of low cost microfluidic chips using a shrinking approach

The present paper describes the production of microfluidic chips using an approach based on shrinkable biocompatible polymers (i.e. agarose) for the production of size controlled microfluidic channels. In addition, all steps of chip production were carried out using an inexpensive approach that uses low cost chemicals and equipment. The produced chips were then validated by producing monodisperse polymeric microparticles for drug delivery and hydrogel microfibers for cell embedding.

Liquid refractive index sensing independent of opacity using an optofluidic diffraction sensor

We have implemented a multifunctional optofluidic sensor that can monitor changes in the refractive index and pressure of biofluid simultaneously and can detect free-solution molecular interaction in situ. In this Letter, we demonstrate two major improvements of this sensor proven by both simulation and experiments. One improvement is the broader measurement range of refractive index by making the diffraction grating with high-index polymer. The other improvement is the separation of refractive index sensing from opacity sensing by using the relative power ratio of diffraction orders. This simple, compact and low-cost multifunctional optofluidic sensor has the potential to be used for in situ biofluid monitoring.

Low cost lab-on-a-chip prototyping with a consumer grade 3D printer

Versatile prototyping of 3D printed lab-on-a-chip devices, supporting different forms of sample delivery, transport, functionalization and readout, is demonstrated with a consumer grade printer, which centralizes all critical fabrication tasks. Devices cost 0.57US$ and are demonstrated in chemical sensing and micromixing examples, which exploit established principles from reference technologies.

A 1024-sample serum analyzer chip for cancer diagnostics

We present a platform that combines microarrays and microfluidic techniques to measure four protein biomarkers in 1024 serum samples for a total of 4096 assays per device. Detection is based on a surface fluorescence sandwich immunoassay with a limit of detection of ~1 pM for most of the proteins measured: PSA, TNF-α, IL-1β, and IL-6. To validate the utility of our platform, we measured these four biomarkers in 20 clinical human serum samples, 10 from prostate cancer patients and 10 female and male controls. We compared the results of our platform to a conventional ELISA and found a good correlation between them. However, compared to a classical ELISA, our device reduces the total cost of reagents by 4 orders of magnitude while increasing throughput by 2 orders of magnitude. Overall, we demonstrate an integrated approach to perform low-cost and rapid quantification of protein biomarkers from over one thousand serum samples. This new high-throughput technology will have a significant impact on disease diagnosis and management.

Rapid, low-cost and instrument-free CD4+ cell counting for HIV diagnostics in resource-poor settings

We present a novel, user-friendly and widely autonomous point-of-care diagnostic to enable HIV monitoring in resource-poor regions where the current pandemic is most prevalent. To specifically isolate magnetically tagged CD4+ cells directly from patient blood, the low-cost and disposable microfluidic chip operates by dual-force CD4+ cell magnetophoresis; whereby the interplay of flow and magnetic fields governs the trajectory of target cells depending on whether the cell binds to a magnetic microbead. Instrument-free pumping is implemented by a finger-actuated elastic membrane; tagged beads are laterally deflected by a small and re-useable permanent magnet. The single-depth and monolithic microfluidic structure can easily be fabricated in a single casting step. After their magnetophoretic isolation from whole blood, estimation of CD4+ cell concentrations is then measured by bright-field inspection of the capture chamber. In addition, an optional fluorescence measurement can be used for confirmation of the bright-field result if required. On-chip CD4+ estimation produces a linear response over the full range of medically relevant CD4+ cell concentrations. Our technology combines high-efficiency capture (93.0 ± 3.3%) and cell enumeration.

Configurable low-cost plotter device for fabrication of multi-color sub-cellular scale microarrays

The construction and operation of a low-cost plotter for fabrication of microarrays for multiplexed single-cell analyses is reported. The printing head consists of polymeric pyramidal pens mounted on a rotation stage installed on an aluminium frame. This construction enables printing of microarrays onto glass substrates mounted on a tilt stage, controlled by a Lab-View operated user interface. The plotter can be assembled by typical academic workshops from components of less than 15,000 Euro. The functionality of the instrument is demonstrated by printing DNA microarrays on the area of 0.5 cm2 using up to three different oligonucleotides. Typical feature sizes are 5 μm diameter with a pitch of 15 μm, leading to densities of up to 10(4)-10(5) spots/mm2. The fabricated DNA microarrays are used to produce sub-cellular scale arrays of bioactive epidermal growth factor peptides by means of DNA-directed immobilization. The suitability of these biochips for cell biological studies is demonstrated by specific recruitment, concentration, and activation of EGF receptors within the plasma membrane of adherent living cells. This work illustrates that the presented plotter gives access to bio-functionalized arrays usable for fundamental research in cell biology, such as the manipulation of signal pathways in living cells at subcellular resolution.

A rapid and sensitive method for hydroxyl radical detection on a microfluidic chip using an N-doped porous carbon nanofiber modified pencil graphite electrode

Hydroxyl radicals (˙OH) play an important role in human diseases. Traditional detection methods are time consuming and require expensive instruments. Here, we present a simple and sensitive method for the detection of hydroxyl radicals on a microfluidic chip using an electrochemical technique. Aniline monomer is electrochemically polymerized on the surface of a pencil graphite electrode and carbonized at 800 °C. The resulting N-doped porous carbon nanofiber-modified pencil graphite electrode is embedded into a microfluidic chip directly as a working electrode. 4-Hydroxybenzoic acid (4-HBA) is selected as the trapping agent owing to its unique 3,4-DHBA product and high trapping efficiency. A low detection limit of 1.0 × 10(-6) M is achieved on the microfluidic chip. As a demonstration, the microfluidic chip is successfully utilized for the detection of ˙OH in cigarette smoke. The strong π-π stacking and hydrophobic interactions between the nitrogen-doped carbon materials and the pencil graphite make the modified electrode well-suited for the microfluidic chip.

The LabTube - a novel microfluidic platform for assay automation in laboratory centrifuges

Assay automation is the key for successful transformation of modern biotechnology into routine workflows. Yet, it requires considerable investment in processing devices and auxiliary infrastructure, which is not cost-efficient for laboratories with low or medium sample throughput or point-of-care testing. To close this gap, we present the LabTube platform, which is based on assay specific disposable cartridges for processing in laboratory centrifuges. LabTube cartridges comprise interfaces for sample loading and downstream applications and fluidic unit operations for release of prestored reagents, mixing, and solid phase extraction. Process control is achieved by a centrifugally-actuated ballpen mechanism. To demonstrate the workflow and functionality of the LabTube platform, we show two LabTube automated sample preparation assays from laboratory routines: DNA extractions from whole blood and purification of His-tagged proteins. Equal DNA and protein yields were observed compared to manual reference runs, while LabTube automation could significantly reduce the hands-on-time to one minute per extraction.

Fast magnetic isolation of simple sequence repeat markers in microfluidic channels

Simple sequence repeat (SSR) markers are widely used for genome mapping, genetic diversity characterization and medical diagnosis. The fast isolation by AFLP of sequence containing repeats (FIASCO) is a powerful method for SSR marker isolation, but it is laborious, costly, and time consuming and requires multiple rounds of washing. Here, we report a superparamagnetic bead (SPMB)-based FIASCO method in a magnetic field controllable microfluidic chip (MFCM-Chip). This method dramatically reduces the assay time by 4.25-fold and reduces the quantity of magnetic beads and probes by 10-fold through the magnetic capture of (AG)n-containing fragments from Herba Leonuri, followed by washing and eluting on a microchip. The feasibility of this method was further evaluated by PCR and sequencing, and the results showed that the proportion of fragments containing SSRs was 89%, confirming that this platform is a fast and efficient method for SSR marker isolation. This cost-effective platform will make the powerful FIASCO technique more accessible for routine use with a wide variety of materials.

Scalable alignment of three-dimensional cellular constructs in a microfluidic chip

There have been considerable efforts to engineer three-dimensional (3D) microfluidic environments to enhance cellular function over conventional two-dimensional (2D) cultures in microfluidic chips, but few involve topographical features, such as micro/nano-grooves, which are beneficial for cell types of cardiac, skeletal and neuronal lineages. Here we have developed a cost-effective and scalable method to incorporate micro-topographical cues into microfluidic chips to induce cell alignment. Using commercially available optical media as molds for replica molding, we produced large surface areas of polydimethylsiloxane (PDMS) micro-grooved substrates and plasma-bonded them to multiple microfluidic chips. Besides aligning a 2D monolayer of cells, the micro-grooved substrate can align 3D cellular constructs on chip. C2C12 mouse myoblasts were cultured three-dimensionally in a microfluidic chip with incorporated PDMS micro-grooved substrate remodeled into an aligned 3D cellular construct, where the actin cytoskeleton and nuclei were preferentially oriented along the micro-grooves. Cells within the 3D cellular constructs can align without being in direct contact with the micro-grooves due to synergism between topography and fluid shear stress. Aligned C2C12 3D cellular constructs showed enhanced differentiation into skeletal muscles as compared to randomly aligned ones. This novel method enables the routine inclusion of micro-topographical cues into 2D or 3D microfluidic cultures to generate relevant physiological models for studying tissue morphogenesis and drug screening applications.

Chip-based liver equivalents for toxicity testing--organotypicalness versus cost-efficient high throughput

Drug-induced liver toxicity dominates the reasons for pharmaceutical product ban, withdrawal or non-approval since the thalidomide disaster in the late-1950s. Hopes to finally solve the liver toxicity test dilemma have recently risen to a historic level based on the latest progress in human microfluidic tissue culture devices. Chip-based human liver equivalents are envisaged to identify liver toxic agents regularly undiscovered by current test procedures at industrial throughput. In this review, we focus on advanced microfluidic microscale liver equivalents, appraising them against the level of architectural and, consequently, functional identity with their human counterpart in vivo. We emphasise the inherent relationship between human liver architecture and its drug-induced injury. Furthermore, we plot the current socio-economic drug development environment against the possible value such systems may add. Finally, we try to sketch a forecast for translational innovations in the field.

A handheld point-of-care genomic diagnostic system

The rapid detection and identification of infectious disease pathogens is a critical need for healthcare in both developed and developing countries. As we gain more insight into the genomic basis of pathogen infectivity and drug resistance, point-of-care nucleic acid testing will likely become an important tool for global health. In this paper, we present an inexpensive, handheld, battery-powered instrument designed to enable pathogen genotyping in the developing world. Our Microfluidic Biomolecular Amplification Reader (µBAR) represents the convergence of molecular biology, microfluidics, optics, and electronics technology. The µBAR is capable of carrying out isothermal nucleic acid amplification assays with real-time fluorescence readout at a fraction of the cost of conventional benchtop thermocyclers. Additionally, the µBAR features cell phone data connectivity and GPS sample geotagging which can enable epidemiological surveying and remote healthcare delivery. The µBAR controls assay temperature through an integrated resistive heater and monitors real-time fluorescence signals from 60 individual reaction chambers using LEDs and phototransistors. Assays are carried out on PDMS disposable microfluidic cartridges which require no external power for sample loading. We characterize the fluorescence detection limits, heater uniformity, and battery life of the instrument. As a proof-of-principle, we demonstrate the detection of the HIV-1 integrase gene with the µBAR using the Loop-Mediated Isothermal Amplification (LAMP) assay. Although we focus on the detection of purified DNA here, LAMP has previously been demonstrated with a range of clinical samples, and our eventual goal is to develop a microfluidic device which includes on-chip sample preparation from raw samples. The µBAR is based entirely around open source hardware and software, and in the accompanying online supplement we present a full set of schematics, bill of materials, PCB layouts, CAD drawings, and source code for the µBAR instrument with the goal of spurring further innovation toward low-cost genetic diagnostics.

CD4 counting technologies for HIV therapy monitoring in resource-poor settings--state-of-the-art and emerging microtechnologies

Modern advancements in pharmaceuticals have provided individuals who have been infected with the human immunodeficiency virus (HIV) with the possibility of significantly extending their survival rates. When administered sufficiently soon after infection, antiretroviral therapy (ART) allows medical practitioners to control onset of the symptoms of the associated acquired immune deficiency syndrome (AIDS). Active monitoring of the immune system in both HIV patients and individuals who are regarded as "at-risk" is critical in the decision making process for when to start a patient on ART. A reliable and common method for such monitoring is to observe any decline in the number of CD4 expressing T-helper cells in the blood of a patient. However, the technology, expertise, infrastructure and costs to carry out such a diagnostic cannot be handled by medical services in resource-poor regions where HIV is endemic. Addressing this shortfall, commercialized point-of-care (POC) CD4 cell count systems are now available in such regions. A number of newer devices will also soon be on the market, some the result of recent maturing of charity-funded initiatives. Many of the current and imminent devices are enabled by microfluidic solutions, and this review will critically survey and analyze these POC technologies for CD4 counting, both on-market and near-to-market deployment. Additionally, promising technologies under development that may usher in a new generation of devices will be presented.

Overview of the microfluidic diagnostics commercial landscape

Since its birth in the late 1980s, the field of microfluidics has continued to mature, with a growing number of companies pursuing diagnostic applications. In 2009 the worldwide in vitro diagnostics market was estimated at >$40 billion USD, and microfluidic diagnostics are poised to reap a significant part of this market across a range of areas including laboratory diagnostics, point-of-care diagnostics, cancer diagnostics, and others. The potential economic advantages of microfluidics are numerous and compelling: lower reagent and/or sample volumes, lower equipment costs, improved portability, increased automation, and increased measurement speed. All of these factors may help put more information in the hands of doctors and patients sooner, enabling earlier disease detection and more tailored, effective treatments. This chapter reviews the microfluidic diagnostics commercial landscape and discusses potential commercialization challenges and opportunities.

A low-cost microfluidic chip for rapid genotyping of malaria-transmitting mosquitoes

BACKGROUND

Vector control is one of the most effective measures to prevent the transmission of malaria, a disease that causes over 600,000 deaths annually. Around 30-40 Anopheles mosquito species are natural vectors of malaria parasites. Some of these species cannot be morphologically distinguished, but have behavioral and ecological differences. Emblematic of this is the Anopheles gambiae species complex. The correct identification of vector species is fundamental to the development of control strategies and epidemiological studies of disease transmission.

METHODOLOGY/PRINCIPAL FINDINGS

An inexpensive, disposable, field-deployable, sample-to-answer, microfluidic chip was designed, constructed, and tested for rapid molecular identification of Anopheles gambiae and Anopheles arabiensis. The chip contains three isothermal amplification reactors. One test reactor operates with specific primers to amplify Anopheles gambiae DNA, another with specific primers for Anopheles arabiensis DNA, and the third serves as a negative control. A mosquito leg was crushed on an isolation membrane. Two discs, laden with mosquito tissue, were punched out of the membrane and inserted into the two test chambers. The isolated, disc-bound DNA served as a template in the amplification processes. The amplification products were detected with intercalating fluorescent dye that was excited with a blue light-emitting diode. The emitted light was observed by eye and recorded with a cell-phone camera. When the target consisted of Anopheles gambiae, the reactor containing primers specific to An. gambiae lit up while the other two reactors remained dark. When the target consisted of Anopheles arabiensis, the reactor containing primers specific to An. arabiensis lit up while the other two reactors remained dark.

CONCLUSIONS/SIGNIFICANCE

The microfluidic chip provides a means to identify mosquito type through molecular analysis. It is suitable for field work, allowing one to track the geographical distribution of mosquito populations and community structure alterations due to environmental changes and malaria intervention measures.

Commercialization of microfluidic point-of-care diagnostic devices

A large part of the excitement behind microfluidics is in its potential for producing practical devices, but surprisingly few lab-on-a-chip based technologies have been successfully introduced into the market. Here, we review current work in commercializing microfluidic technologies, with a focus on point-of-care diagnostics applications. We will also identify challenges to commercialization, including lessons drawn from our experience in Claros Diagnostics. Moving forward, we discuss the need to strike a balance between achieving real-world impact with integrated devices versus design of novel single microfluidic components.

Microfluidic diagnostics for the developing world

For more than a decade, it has been expected that microfluidic technology would revolutionize the healthcare industry with simple, inexpensive, effective, and ubiquitous miniature diagnostic devices. To date, however, microfluidics has not yet been able to live up to these expectations. This fact has led to the recent development of new philosophies and methodologies for microfluidic diagnostics. In this Focus article, we will discuss some of the latest breakthroughs that could significantly impact medical diagnostics in the developing world.

Immunosensor towards low-cost, rapid diagnosis of tuberculosis

A rapid, accurate tuberculosis diagnostic tool that is compatible with the needs of tuberculosis-endemic settings is a long-sought goal. An immunofluorescence microtip sensor is described that detects Mycobacterium tuberculosis complex cells in sputum in 25 minutes. Concentration mechanisms based on flow circulation and electric field are combined at different scales to concentrate target bacteria in 1 mL samples onto the surfaces of microscale tips. Specificity is conferred by genus-specific antibodies on the microtip surface. Immunofluorescence is then used to detect the captured cells on the microtip. The detection limit in sputum is 200 CFU mL(-1) with a success rate of 96%, which is comparable to PCR.

Microfluidic nanoplasmonic-enabled device for multiplex DNA detection

We describe a rapid, quantitative, multiplex, self-labelled, and real-time DNA biosensor employing Ag nanoparticle-bound DNA hairpin probes immobilized in a microfluidic channel. Capture of complementary target DNAs by the microarrayed DNA hairpin probes results in a positive fluorescence signal via a conformational change of the probe molecules, signalling the presence of target DNAs. The device's capability for quantitative analyses was evaluated and a detection time as low as 6 min (with a target flow rate of 0.5 μl min(-1)) was sufficient to generate significant detection signals. This detection time translates to merely 3 μl of target solution consumption. An unoptimized sensitivity of 500 pM was demonstrated for this device.

A low cost point-of-care viscous sample preparation device for molecular diagnosis in the developing world; an example of microfluidic origami

The lab-on-a-chip concept has led to several point-of-care (POC) diagnostic microfluidic platforms. However, few of these can process raw samples for molecular diagnosis and fewer yet are suited for use in a resource-limited setting without permanent electrical infrastructure. We present here a very low cost paper microfluidic device for POC extraction of bacterial DNA from raw viscous samples--a challenge for conventional microfluidic platforms. This is an example of "microfluidic origami" in that the system is activated by folding; demonstrated here is room temperature cell lysis and DNA extraction from pig mucin (simulating sputum) spiked with E. coli without the use of external power. The microfluidic origami device features dry reagent storage and rehydration of the lysis buffer. We demonstrate DNA extraction from samples with a bacterial load as low as 33 CFU ml(-1). Extraction times, starting from the raw sample, have been optimized to about 1.5 h without the use of external power, or to within 1 h using an oven or a heater block. The fabrication of this paper microfluidic device can be translated into high volume production in the developing world without the need for a semiconductor clean room or a microfabrication facility. The sample preparation can be performed with the addition of just the sample, water, ethanol and elute buffer to the device, thus reducing chemical hazards during transport and handling.

Miniaturized lensless imaging systems for cell and microorganism visualization in point-of-care testing

Low-cost, robust, and user-friendly diagnostic capabilities at the point-of-care (POC) are critical for treating infectious diseases and preventing their spread in developing countries. Recent advances in micro- and nanoscale technologies have enabled the merger of optical and fluidic technologies (optofluidics) paving the way for cost-effective lensless imaging and diagnosis for POC testing in resource-limited settings. Applications of the emerging lensless imaging technologies include detecting and counting cells of interest, which allows rapid and affordable diagnostic decisions. This review presents the advances in lensless imaging and diagnostic systems, and their potential clinical applications in developing countries. The emerging technologies are reviewed from a POC perspective considering cost effectiveness, portability, sensitivity, throughput and ease of use for resource-limited settings.

Sheathless elasto-inertial particle focusing and continuous separation in a straight rectangular microchannel

Particle focusing in planar geometries is essentially required in order to develop cost-effective lab-on-a-chips, such as cell counting and point-of-care (POC) devices. In this study, a novel method for sheathless particle focusing, called "Elasto-Inertial Particle Focusing", was demonstrated in a straight microchannel. The particles were notably aligned along the centerline of the straight channel under a pressure-driven flow without any additional external force or apparatus after the addition of an elasticity enhancer: PEO (poly(ethylene oxide)) (∼O(100) ppm). As theoretically predicted (elasticity number: El≈O(100)), multiple equilibrium positions (centerline and corners) were observed for the viscoelastic flow without inertia, whereas three-dimensional particle focusing only occurred when neither the elasticity nor the inertia was negligible. Therefore, the three-dimensional particle focusing mechanism was attributed to the synergetic combination of the elasticity and the inertia (elasticity number: El≈O(1-10)). Furthermore, from the size dependence of the elastic force upon particles, we demonstrated that a mixture of 5.9 and 2.4 µm particles was separated at the exit of the channel in viscoelastic flows. We expect that this method can contribute to develop the miniaturized flow cytometry and microdevices for cell and particle manipulation.

Sheathless elasto-inertial particle focusing and continuous separation in a straight rectangular microchannel

Particle focusing in planar geometries is essentially required in order to develop cost-effective lab-on-a-chips, such as cell counting and point-of-care (POC) devices. In this study, a novel method for sheathless particle focusing, called "Elasto-Inertial Particle Focusing", was demonstrated in a straight microchannel. The particles were notably aligned along the centerline of the straight channel under a pressure-driven flow without any additional external force or apparatus after the addition of an elasticity enhancer: PEO (poly(ethylene oxide)) (∼O(100) ppm). As theoretically predicted (elasticity number: El≈O(100)), multiple equilibrium positions (centerline and corners) were observed for the viscoelastic flow without inertia, whereas three-dimensional particle focusing only occurred when neither the elasticity nor the inertia was negligible. Therefore, the three-dimensional particle focusing mechanism was attributed to the synergetic combination of the elasticity and the inertia (elasticity number: El≈O(1-10)). Furthermore, from the size dependence of the elastic force upon particles, we demonstrated that a mixture of 5.9 and 2.4 µm particles was separated at the exit of the channel in viscoelastic flows. We expect that this method can contribute to develop the miniaturized flow cytometry and microdevices for cell and particle manipulation.

Practical approach for macroporous structure embedded microfluidic system and the catalytic microchemical application

We present a low cost and practical approach to integrate 3D ordered macroporous polyfluoropolyether (PFPE) patterns into a microchannel by a series of porous pattern fabrication processes and subsequent photolithography in a site- and shape-selective manner. The 3D ordered macroporous patterns with high-resolution edges were firstly fabricated by microtransfer molding (μ-TM) of the sacrificial polystyrene (PS) template infiltrated with PFPE as a non-adhesive and solvent-resistant skeletal material. The resulting robust PFPE porous structures with high solvent resistance on a silicon wafer can easily be embedded into the microchannel with the aid of conventional photolithography, leading to a microfluidic system with a built-in microstructure. Moreover, catalytic Pd nanoparticles implanted on the surface of the porous structure were obtained by use of Pd nanoparticle deposited PS spheres, the porous structure embedded channel was utilized to perform a Suzuki coupling reaction.

Fully integrated lab-on-a-disc for simultaneous analysis of biochemistry and immunoassay from whole blood

We report a fully integrated device that can perform both multiple biochemical analysis and sandwich type immunoassay simultaneously on a disc. The whole blood is applied directly to the disposable "lab-on-a-disc" containing different kinds of freeze-dried reagents for the blood chemistry analysis as well as reagents required for the immunoassay. The concentrations of different kinds of analytes are reported within 22 min by simply inserting a disc to a portable device. Using the innovative laser irradiated ferrowax microvalves together with the centrifugal microfluidics, the total process of plasma separation, metering, mixing, incubation, washing, and detection is fully automated. The analyzer is equipped with an optical detection module to measure absorbances at 10 different wavelengths to accommodate the various kinds of reaction protocols. Compared to the conventional blood analysis done in clinical laboratories, it is advantageous for point-of-care applications because it requires a smaller amount of blood (350 μL vs. 3 mL), takes less time (22 min vs. several days), does not require specially trained operators or expensive instruments to run biochemical analysis and immunoassay separately.

An efficient and high-throughput electroporation microchip applicable for siRNA delivery

Here we report a novel electroporation microchip with great performance and compatibility with the standard multi-well plate used in biological research. The novel annular interdigitated electrode design makes it possible to achieve efficient cell transfection as high as 90% under low-strength electrical pulses, thereby circumventing the many adverse effects of conventional cuvette-type and previously reported microchip-based electroporation devices. Using this system, we demonstrated substantially improved cell transfection efficacy and viability in cultured and primary cells, for both plasmid and synthetic siRNA. Improvements of this system open new opportunities for high-throughput applications of siRNA technology in basic and biomedical research.