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Gas-permeable membranes (GPMs) and membrane-like micro-/nanostructures offer precise control over the transport of liquids, gases, and small molecules on microchips, which has led to the possibility of diverse applications, such as gas sensors, solution concentrators, and mixture separators. With the escalating demand for GPMs in microfluidics, this Perspective article aims to comprehensively categorize the transport mechanisms of gases through GPMs based on the penetrant type and the transport direction. We also provide a comprehensive review of recent advancements in GPM-integrated microfluidic devices, provide an overview of the fundamental mechanisms underlying gas transport through GPMs, and present future perspectives on the integration of GPMs in microfluidics. Furthermore, we address the current challenges associated with GPMs and GPM-integrated microfluidic devices, taking into consideration the intrinsic material properties and capabilities of GPMs. By tackling these challenges head-on, we believe that our perspectives can catalyze innovative advancements and help meet the evolving demands of microfluidic applications. [ABSTRACT FROM AUTHOR]

Today, the search for disease biomarkers and techniques for their detection is one of the most important focuses in modern healthcare. Extracellular vesicles (EVs) are known to be related to the pathogenesis of various illnesses, such as cancer, neurodegenerative disease, and cardiovascular disease. Specific EV detection and potential control of their amount in biological fluids can provide a promising therapeutic strategy that involves reduction in EV production and circulation to normal levels to prevent disease progression. To provide a foundation for such research and development, we report the application of photonic integrated circuits in the form of a Mach–Zehnder interferometer coupled with microfluidics for monitoring each step of a covalent linkage between receptors and silicon nitride. We show that such a biosensor can be used for biological marker quantification, such as EVs containing a specific membrane protein HER2. The developed platform provides real-time results by using microliter volumes of the test sample. This research can be used as a first step toward creation of a laboratory on a chip for the precise control of coating in terms of chemical applications and monitoring the effectiveness of the chosen treatment for medical applications. [ABSTRACT FROM AUTHOR]

Different from the classical periodic‐resonator‐based metamaterials, epsilon‐near‐zero (ENZ) metamaterials provide a unique paradigm to achieve equivalent electromagnetic characteristics in deep subwavelength scales, exhibiting unprecedented impacts on a broad variety of extreme‐small‐volume applications. By doping regular dielectric rods in the ENZ host, the effective permeability µeff of ENZ metamaterials is properly tuned for desired scattering properties and intrinsic impedance. However, losses in ENZ metamaterials severely limit the tuning range of the real part of µeff and result in an undesired imaginary part. Here, to mitigate the loss issue of ENZ metamaterials, a dielectric‐free approach is theoretically studied and experimentally verified by substituting dielectric dopants with metal‐layer dopants to construct a low‐loss resonant cavity. Therefore, the largest tuning range of µeff is achieved, which advances ENZ metamaterials from ideal cases to more extensive and practical applications. In addition to existing photonics and electronics applications of regular ENZ metamaterials, additional examples are studied to demonstrate the low‐loss benefits of layer‐type ENZ metamaterials, including integrated microfluidic switches and high‐sensitivity sensors with a sensitivity of 11.2% and quality factor of 2800. These examples reveal universal significance for wide‐range applications in extreme‐small‐volume devices and systems, such as integrated circuits, chips, and implanted devices. [ABSTRACT FROM AUTHOR]

A lab-on-a-chip (LOC) is a device that facilitates the incorporation of a concatenation of various laboratory functions on a unique integrated circuit. The size of this instrument is merely a few millimeters to centimeters designed to attain automation and high-throughput screening. Microfluidic systems used in LOC devices allow the manufacture of millions of microchannels, each measuring mere micrometers. These microchannels enable control of fluids in infinitesimal quantities for a variety of diagnoses. Several labs on a chip have been commercialized in recent times for fundamental procedures, including glucose monitoring, human immunodeficiency virus, early tumor detection, and cardiac diagnostics. The LOC integrates microfluidics, nanosensors, micro-electrics, and biochemistry on one device. The advantages of the chip include its sustainability and cutback wastage. It expedites a decline in reagent costs and requires minimal sample volumes. The analysis and response are faster and the response is better controlled by equipping micro-channels. Countries with exiguous healthcare are in the face of adversity due to increased fatality rates from infectious diseases that are often curable in developed nations. In certain circumstances, impoverished healthcare clinics have the medications requisite to treat a specific condition but are in dearth of the diagnostic equipment needed to determine, in which individuals are in need of the medications. This is where the role of LOC as a potent novel diagnostic instrument would benefit humankind in the nearest future, according to eminent researchers. This article highlights the applications of LOC in a miscellany of fields, its advantages, feasible means to overcome the drawbacks, and the propitious prospects of this technology. [ABSTRACT FROM AUTHOR]

Since the field's inception, pioneers in microfluidics have made significant progress towards realizing complete lab-on-chip systems capable of sophisticated sample analysis and processing. One avenue towards this goal has been to join forces with the related field of microelectronics, using integrated circuits (ICs) to perform on-chip actuation and sensing. While early demonstrations focused on using microfluidic–IC hybrid chips to miniaturize benchtop instruments, steady advancements in the field have enabled a new generation of devices that expand past miniaturization into high-performance applications that would not be possible without IC hybrid integration. In this review, we identify recent examples of labs-on-chip that use high-resolution, high-speed, and multifunctional electronic and photonic chips to expand the capabilities of conventional sample analysis. We focus on three particularly active areas: a) high-throughput integrated flow cytometers; b) large-scale microelectrode arrays for stimulation and multimodal sensing of cells over a wide field of view; c) high-speed biosensors for studying molecules with high temporal resolution. We also discuss recent advancements in IC technology, including on-chip data processing techniques and lens-free optics based on integrated photonics, that are poised to further advance microfluidic–IC hybrid chips. [ABSTRACT FROM AUTHOR]

Deterministic lateral displacement (DLD) is a passive separation method that separates particles by hydrodynamic size. This label-free method is a promising technique for cell separation because of its high size resolution and insensitivity to flow rate. Development of capillary-driven microfluidic technologies allows microfluidic devices to be operated without any external power for fluid pumping, lowering their total cost and complexity. Herein, we develop and test a DLD-based particle and cell sorting method that is driven entirely by capillary pressure. We show microchip self-filling, flow focusing, flow stability, and capture of separated particles. We achieve separation efficiency of 92% for particle–particle separation and more than 99% efficiency for cell–particle separation. The high performance of driven flow and separation along with simplicity of the operation and setup make it a valuable candidate for point-of-care devices. [ABSTRACT FROM AUTHOR]

Photolithographic patterning of components and integrated circuits based on active polymers for microfluidics is challenging and not always efficient on a laboratory scale using the traditional mask-based fabrication procedures. Here, we present an alternative manufacturing process based on multi-material 3D printing that can be used to print various active polymers in microfluidic structures that act as microvalves on large-area substrates efficiently in terms of processing time and consumption of active materials with a single machine. Based on the examples of two chemofluidic valve types, hydrogel-based closing valves and PEG-based opening valves, the respective printing procedures, essential influencing variables and special features are discussed, and the components are characterized with regard to their properties and tolerances. The functionality of the concept is demonstrated by a specific chemofluidic chip which automates an analysis procedure typical of clinical chemistry and laboratory medicine. Multi-material 3D printing allows active-material devices to be produced on chip substrates with tolerances comparable to photolithography but is faster and very flexible for small quantities of up to about 50 chips. [ABSTRACT FROM AUTHOR]

Top‐down mass spectrometry (TD‐MS) provides unique information on compositions, structures, and functions of proteins or protein complexes and has been recognized as a powerful approach to complement conventional tools in protein analysis. Employing microfluidic chips in TD‐MS workflows offers unique advantages including flexible integration and automation of multiple sample treatment functions, lowered sample consumption, compatibility with high‐sensitive ionization and higher throughput. Here we reviewed the reported microchips developed for TD‐MS in aspects of design of ionization, separation and mixing modules, and fabrication approaches; we also attempted to summarize the design considerations that may inspire development of microchips with better performance and wider applications. [ABSTRACT FROM AUTHOR]

With the recent great interest in microfluidic devices, a better understanding of preconcentration technology has become increasingly important. Herein, concentration enrichment of charged samples is achieved by using field-amplified sample stacking (FASS) technology in the microchannel. This paper aims to develop a fundamental understanding of FASS and to propose a method to enhance the enrichment quality of FASS. First, numerical investigations are carried out to systematically study the effects of various parameters including the applied voltage, the charged properties of the sample, the buffer concentration ratio, the injection length, and the microchannel width on FASS enrichment performance. The results show that reducing the width of the microchannel is an effective way to improve the enrichment quality. The maximum enrichment ratio can be improved by 67.35% by reducing the width of the microchannel to less than 10 μm due to the inhibition of background buffer diffusion. Second, to improve traditional FASS performance, a high-conductance gradient boundary is established by photoinitiating fabrication of a porous plug at the enriched interface position. This structure provides a region that reduces the local size of the internal channel to less than 5 μm and has high flow resistance, but allows the electromigration of the charged analyte. Experimental results show that an electropherogram signal increases by a maximum factor of 329 in electrophoretic enrichment of fluorescein–Na with 5 × 10−7 M initial concentrations, and the enrichment quality of traditional FASS is greatly improved. [ABSTRACT FROM AUTHOR]

Cell analysis at the single-cell level is of great importance to investigate the inherent heterogeneity of cell populations and to understand the morphology, composition, and function of individual cells. With the continuous innovation of analytical techniques and methods, single-cell analysis on microfluidic chip systems has been extensively applied for its precise single-cell manipulation and sensitive signal response integrated with various detection techniques, such as optical, electrical, and mass spectrometric analyses. In this review, we focus on the specific optical events in single-cell analysis on a microfluidic chip system. First, the four most commonly applied optical technologies, i.e., fluorescence, surface-enhanced Raman spectroscopy, surface plasmon resonance, and interferometry, are briefly introduced. Then, we focus on the recent applications of the abovementioned optical technologies integrated with a microfluidic chip system for single-cell analysis. Finally, future directions of optical technologies for single-cell analysis on microfluidic chip systems are predicted. [ABSTRACT FROM AUTHOR]

A microfluidic chip is introduced for generating double emulsion droplets, consisting of a coaxial focusing center structure combined with a flow-focusing structure. The volume of fluid method (VOF) was adopted to numerically simulate and validate the formation of double emulsion droplets in the device. The impact of microfluidics on the dimensions and molding position of double emulsion droplets was examined under varying flow parameters and physical properties. Results demonstrate that the impact of the alteration in the flow rate of the middle phase is pivotal in the droplet generation process in comparison to the outer phase. An increase in the flow rate of the middle phase results in a notable enlargement of the double emulsion droplets. An increase in viscosity affects the forming regime, causing a transition in the droplet regime. Furthermore, interfacial tension exerts a notable impact on the positioning of droplet formation. The microfluidic device outlined in this paper effectively generates double emulsion droplets characterized by high monodispersity and excellent stability, which serves as a new reference for the practical generation of double emulsion droplets. [ABSTRACT FROM AUTHOR]

Aptamer-based electrochemical sensors are frequently used as independent, surface-functionalized, passive electrodes. However, their sensitivity and detection limits become limited, particularly when the electrode area is reduced to facilitate miniaturization. A mobile phone-based microfluidic electrochemical aptamer sensing platform for 3,3′,4,4′-tetrachlorobiphenyl (PCB77) detection was developed in this work. This aptamer sensor utilized Exonuclease I (Exo I) and DNA/AuNPs/horseradish peroxidase (DNA/AuNPs/HRP) nanoprobes as a merged signal amplification method, which resulted in an increase in the electrochemical sensing performance. Sensitive detection of PCB77 was accomplished by functionalizing the hierarchically structured Au@MoS 2 /CNTs/GO modified working/sensing electrode with the specific aptamer. The aptamer sensor was tested with different concentrations of PCB77 within the microfluidic platform. Afterward, the differential pulse voltammograms were recorded using a wireless integrated circuit device. Subsequently, the collected data was transmitted to a smartphone using Bluetooth communication. A detection limit of 0.0085 ng/L was obtained for PCB77 detection, with a detection range from 0.1 to 1000 ng/L. In addition, the detection of PCB77 in spiked water samples validated the possibility of using this aptamer sensor in a real environment, and the aptamer sensor demonstrated high selectivity in distinguishing PCB77 from other potential interfering species. The merging of electrochemical aptamer sensors with purposefully engineered microfluidic and integrated devices in this study is a novel and promising method that provides a dependable platform for on-site applications. [Display omitted] [ABSTRACT FROM AUTHOR]

DNA elongation induced by fluidic stress was investigated on a microfluidic chip composed of a large inlet pool and a narrow channel. Through single-DNA observation with fluorescence microscopy, the manner of stretching of individual T4 DNA molecules (166 kbp) was monitored near the area of accelerating flow with narrowing streamlines. The results showed that the DNA long-axis length increased in a sigmoidal manner depending on the magnitude of flow acceleration, or shear, along the DNA chain. To elucidate the physical mechanism of DNA elongation, we performed a theoretical study by adopting a model of a coarse-grained nonlinear elastic polymer chain elongated by shear stress due to acceleration flow along the chain direction. [ABSTRACT FROM AUTHOR]

This invited paper reviews the progress of silicon-based integrated analyzers for biomedical applications over the last two decades. Focus is set on various integrated circuit realizations in the millimeter-wave range from 30 GHz and at the terahertz frequencies of above 300 GHz. This article discusses high-frequency architectures and concrete implementations of both narrowband as well as broadband integrated readout circuits, including their use in miniaturized sensor solutions. A variety of circuits ranging from low-power sensing oscillators to highly integrated broadband vector network analyzers (VNAs), and example realizations of millimeter-wave cardiovascular sensors and implants to THz microfluidic labs-on-chip and exhaled human breath analyzers are recapitulated. This article closes with an outlook on emerging fields of research for future advancement of such biomedical sensors toward reliable and specific systems. [ABSTRACT FROM AUTHOR]

Inertial microfluidic devices continue to show promise for label-free separation of cells from liquid biopsies and other biological samples. Serpentine-channel microfluidic devices capitalizing on inertial forces such as Dean flow have been demonstrated for cell separation, but are limited in performance due to the magnitude of the inertial lift and drag force gradients across the separation channel. We have developed a new flow design that uses periodic channel contractions to enhance the magnitude of the force gradient. Separation recover was 97% with the final sorter output consisting of 78% target cells. Separation efficiency was 87% for whole blood, which could be increased to 97% if the sample was diluted prior to sorting. The enrichment of cancer cells was over 1000-fold, and sorted cancer cells maintained a viability of 93.8% for 96 hours after sorting. In the analysis of blood plasma, breast cancer cells from a clinical patient were enriched 20×. The incorporation of periodic channel contractions in a Dean flow circuit resulted in an increase in Dean flow gradient according to simulation, resulting in sorting of small-diameter cancer cells in blood samples. [ABSTRACT FROM AUTHOR]

The goal of this work is to classify and quantify the factors that govern polyelectrolyte–surfactant complexation in microfluidic confinement and optimize the designs and operating modes of microfluidic reactors to offer additional advantages over the macroscopic synthesis of such complexes. We analyze and solve a system of governing convection–diffusion–reaction equations to conveniently represent these factors or their combinations as dimensionless similarity criteria. We discuss how these factors contribute to the on-chip control of the reaction initiation, the complex product distribution in a microfluidic device, and the phase behavior of the confined reacting flows and experimentally verify the results in microchips. This approach allows for designing microfluidic devices and setting their operating modes to avoid undesirable clogging by reaction products, control the initiation of the complexation reaction, and produce polyelectrolyte–surfactant aggregates with a broader size range and reduced dispersity. [ABSTRACT FROM AUTHOR]

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Transition metal phosphides with properties similar to platinum metal have received increasing attention for the non-enzymatic detection of glucose. However, the requirement of highly corrosive reagent during sample pretreatment would impose a potential risk to the human body, limiting their practical applications. In this study, we report a self-powered microfluidic device for the non-enzymatic detection of glucose using nickel phosphide (Ni 2 P) hybrid as the catalyst. The Ni 2 P hybrid is synthesized by pyrolysis of metal-organic framework (MOF)-based precursor and in-situ phosphating process, showing two linear detection ranges (1 μM–1 mM, 1 mM–6 mM) toward glucose with the detection limit of 0.32 μM. The good performance of Ni 2 P hybrid for glucose is attributed to the synergistic effect of Ni 2 P active sites and N-doped porous carbon matrix. The microchip is integrated with a NaOH-loaded paper pad and a capillary-based micropump, enabling the automatic NaOH redissolution and delivery of sample solution into the detection chamber. Under the optimized condition, the Ni 2 P hybrid-based microchip realized the detection of glucose in a user-friendly way. Besides, the feasibility of using this microchip for glucose detection in real serum samples has also been validated. This article presents a facile fabrication method utilizing a MOF template to synthesize a Ni 2 P hybrid catalyst. By leveraging the synergy between the Ni 2 P active sites and the N-doped carbon matrix, an exceptional electrochemical detection performance for glucose has been achieved. Additionally, a self-powered chip device has been developed for convenient glucose detection based on the pre-established high pH environment on the chip. [Display omitted] • A facile method was developed to synthesize nickel phosphide hybrid for glucose sensing. • A self-powered microfluidic device was designed to realize the automatic sample delivery. • High pH environment was pre-established on the chip for detection operation. • The microchip was successfully applied to determine the glucose concentration in real samples. [ABSTRACT FROM AUTHOR]

Swine viral diseases challenge the sector's sustainability by affecting productivity and the health and welfare of the animals. The lack of antiviral drugs and/or effective vaccines renders early and reliable diagnosis the basis of viral disease management, underlining the importance of point-of-care (POC) diagnostics. A novel POC diagnostic device utilizing photonic integrated circuits (PICs), microfluidics, and information and communication technologies for the detection of porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza A (SIV) was validated using spiked and clinical oral fluid samples. Metrics including sensitivity, specificity, accuracy, precision, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated to assess the performance of the device. For PRRSV, the device achieved a sensitivity of 83.5%, specificity of 77.8%, and DOR values of 17.66, whereas the values for SIV were 81.8%, 82.2%, and 20.81, respectively. The POC device and PICs can be used for the detection of PRRSV and SIV in the field, paving the way for the introduction of novel technologies in the field of animal POC diagnostics to further optimize livestock biosecurity. [ABSTRACT FROM AUTHOR]

In this study, a system of automatic microparticle patterning that could enable the separation, trapping, and translation of single microbeads in liquid suspension using negative dielectrophoresis (DEP) tweezers was presented to form a single-bead pattern. A microchip with integrated electrodes was flipped and placed above the substrate through a micromanipulator. Microparticles laying on the substrate could be displaced to different positions relative to the electrodes on the microchip, and only the selected particles would be trapped by the electric fields generated from electrodes. Vision-based approaches were used to evaluate the necessary information, such as the gap distance and the positions of electrodes and microparticles in the image. A strategy for separating nearby particles was proposed to achieve single-bead patterning with high accuracy. A controller was used to guide the microparticles toward the position for trapping while avoiding flow disturbance. Different strategies were simulated to decrease the patterning time and find the minimum traveling distance and the best route of movement. The optimization problem is NP-hard. Hence, global optimization algorithms, such as genetic algorithm, particle swarm optimization, and ant colony optimization (ACO), were simulated, and the results were compared with those of the local optimization method. The comparison results showed that ACO obtained the best performance among the methods. The strategy for constructing high-quality microparticle patterns was also examined through experiments. Orange fluorescent polystyrene beads suspended in 6-aminohexanoic acid solution were considered and successfully patterned on a glass substrate by using the proposed system. Note to Practitioners—Micropatterning is an effective tool for pharmaceutical research and drug discovery. However, the reliability of results depends on the quality of patterns. Existing approaches, such as microfluidic devices, are limited to create a pattern from one chip for single use, and the entire process is sealed and isolated from the environment. In this study, a multielectrode microchip combined with a vision-based micromanipulator is introduced to create a novel noncontact approach for microparticle patterning, which offers high flexibility and guarantees the quality of the constructed patterns. The electrodes on the chip can be selectively energized to determine the shape of the final pattern. A real-time screening is performed so that the micromanipulator will only guide the particles in good condition for selection. An optimization algorithm is implemented to aid the particle selection with the electrodes, allowing high-quality microparticle patterns to be constructed in a short time for various applications. [ABSTRACT FROM AUTHOR]

Continuous-flow microfluidic biochips (CFMBs), also known as lab-on-a-chip platforms, have attracted considerable attentions in the past two decades and have been widely used in various laboratory procedures in biomedicine and biochemistry such as point-of-care diagnosis and protein crystallization. Besides a completely automatic execution procedure, these micrometerscale devices offer several advantages over the conventional fluidic platforms, e.g., low sample/reagent consumption, low manufacturing cost, and high execution efficiency. However, similar to the early development of integrated circuits, as the feature size of biochips keeps shrinking, tens of thousands microvalves can now be integrated into a single chip. Consequently, traditional manual-based chip design is no longer suitable and Computer-aided Design (CAD) tools have to be introduced to deal with the large-scale integration of such chips. This paper presents a comprehensive review of recent advances in the design automation of CFMBs, including CAD techniques for architecture synthesis, volume assignment and sample preparation, testing, fault-tolerant design, and washing. These tools have great significance in advancing the automation level of biochip design and further promote their wide adoption. Finally, future trends and potential research topics are discussed in detail to further improve the performance of CFMBs. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases (CVDs) claimed the lives of nearly 21 million people worldwide in 2021, accounting for 30% of global deaths. However, one in five CVD patients is unaware that they have the disease, emphasizing the need for accurate biomarker monitoring. Herein we developed an integrated microfluidic system (IMS) for rapid quantification of four CVD biomarkers, including N-terminal pro B-type natriuretic peptide (NT-proBNP), fibrinogen, cardiac troponin I (cTnI), and C-reactive protein (CRP)- via aptamer-coated interdigitated electrodes (IDE) with integrated circuits (IC) and a self-driven IMS for sample treatment. The device was composed of plasma filtration, metering, and fluidic delay modules, and the former could extract 45% of plasma from a 20-μL blood sample; the metering module could quantify 5 μL of plasma within 90 s. Subsequently, the plasma was transported to a detection chamber, where IC-based IDE sensors made measurements within 5 min. The entire 15-min process allowed us to evaluate biomarkers across a wide dynamic range: NT-proBNP (0.1–10,000 pg/mL), fibrinogen (50-1,000 mg/dL), cTnI (0.1–10,000 pg/mL), and CRP (0.5-9 mg/L). Given that spiked blood samples were measured with reasonable accuracy (>80%), the IMS could see utility in CVD risk assessment and personalized medicine. [ABSTRACT FROM AUTHOR]

• Doubly clamped self-adaptive acting as vortex generators for improved heat transfer inside a micro heat sink. • The working principle of self-adaptive fins is analytically defined. • The influence of doubly clamped fins on the overall performance of micro heat sinks is numerically evaluated. • The heat sinks evaluated are based on microchannels and microfluidic cells. • Heat transfer enhancements of up to 40% and pumping power reductions of 13% are achieved. The continuous increase in the power density of integrated circuits (ICs) has placed thermal management as a key focus for the ICT community. Current liquid cooling systems are usually not optimized for the real operating conditions of advanced electronics, which have heat loads that can vary in time and space. Hence, conventional cooling devices lead to non-uniform temperature patterns at the package level and overcooled systems. This work proposes the use of thermally adaptive actuators, based on doubly clamped fins able to change its shape with temperature, to improve the performance of micro heat sinks with an optimized adaptation to temporal and spatially variable thermal parameters. The effect of this thermally responsive bistable fins on the efficiency of two different micro heat sinks (MHS), one based on microchannels and other on a matrix of microfluidic cells, is numerically evaluated. Results demonstrated a maximum heat transfer enhancement of 40% when adding the clamped-clamped fins within a microchannel and 20% when the fins were placed inside a microfluidic cell. Additionally, savings on hydraulic pumping power have been quantified between 8% and 11%. [ABSTRACT FROM AUTHOR]

Single-cell analysis to investigate cellular heterogeneity and cell-to-cell interactions is a crucial compartment to answer key questions in important biological mechanisms. Droplet-based microfluidics appears to be the ideal platform for such a purpose because the compartmentalization of single cells into microdroplets offers unique advantages of enhancing assay sensitivity, protecting cells against external stresses, allowing versatile and precise manipulations over tested samples, and providing a stable microenvironment for long-term cell proliferation and observation. The present Review aims to give a preliminary guidance for researchers from different backgrounds to explore the field of single-cell encapsulation and analysis. A comprehensive and introductory overview of the droplet formation mechanism, fabrication methods of microchips, and a myriad of passive and active encapsulation techniques to enhance single-cell encapsulation efficiency were presented. Meanwhile, common methods for single-cell analysis, especially for long-term cell proliferation, differentiation, and observation inside microcapsules, are briefly introduced. Finally, the major challenges faced in the field are illustrated, and potential prospects for future work are discussed. [ABSTRACT FROM AUTHOR]

Microfluidic applications require the optimization of chip structure and dimensions. The quick and easy fabrication of chips plays an important role in the progress of research. However, the standard soft lithography technique requires several hours to produce a replication mold. Shortening the mold fabrication time still faces some challenges. We present a fast and easy method to fabricate a positive mold for multi-layer or 3D microdevice construction. Single-layer positive molds with triangular, rectangular, and circular patterns were produced in less than 50 min. A depth-to-width ratio is achieved in the range of 0.6–2.4 and the minimum pattern size reached 50 µm. One additional layer only increases the total time by 5 min. Based on the fabricated positive molds, we created microchips with different depth channels and 3D structures, realizing the cross-flow of multiple liquids and the large-scale production of mono-disperse droplets with controllable size. By using the formed droplets as templates, hydrogel particles with controllable structures were synthesized uniformly. The established method is fast, simple, and compatible with standard soft lithography equipment, displaying the potential to accelerating research progress. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidic devices are a well-established and highly potential Labs-on-Chip technology as droplets are especially suited to encapsulate biological samples like cells, proteins, or DNA. These droplets are injected in a continuous phase and flow through closed microchannels to modules executing operations on the droplets—eventually realizing a (bio-)chemical experiment. Moreover, this technology even allows for the realization of multiple experiments on a single device by letting droplets take different paths through the microfluidic network. This requires, however, a mechanism to route the droplets along these paths. To this end, the concept of passive droplet routing has been suggested which entirely avoids complex valves or switches and, instead, realizes the routing by exploiting the hydrodynamic effect that a droplet will always flow along the path with the highest volumetric flow rate. Since droplets themselves affect the volumetric flow rate, a dedicated sequence of droplets can define what path is taken and, hence, what experiment is executed. However, determining such a droplet sequence is a nontrivial task, as it is nonobvious how much droplets are needed, when to inject them, and how they are interacting. In this paper, we are addressing this issue by providing, for the first time, an automatic method for the generation of droplet sequences realizing the desired experiments on a given network. Evaluations confirm the practicability of the proposed solution. Moreover, the suitability of the obtained droplet sequences is additionally validated through simulations on the 1D analysis model. [ABSTRACT FROM AUTHOR]

The minimization of the sample quantities required by analytical laboratories, as well as the increase of the fastness of the analytical operations are emerging axes for improved radiochemical analyses related to D&D issues. Two microsystem-based protocols were developed for the selective recovery of 55Fe from radioactive samples by solvent extraction. Both protocols were tested on iron solutions in two different microchips. The yields of Fe extraction were compared with macroscale batch experiments. Better performances with more than 80% of iron extracted were obtained with the second protocol, which is based on a reactive transfer of the iron cation, and more suited to the use of microchannels and very low contact times. This study already demonstrate the high potential of microfluidic technology to improve analytical operations on D&D samples. This method will further be validated with radioactive samples. [ABSTRACT FROM AUTHOR]

Dielectrophoresis (DEP) is an effective technique for manipulating particles in microfluidic devices. The DEP force depends on the frequency and square gradient of the electric field, as well as the fluid and particle dielectric properties. An efficient system for manipulating particles can be designed by adjusting these factors. This study aims to develop an efficient microsystem for particle trapping using dual-frequency DEP force. The microfluidic system is divided into two parts of focusing and attracting. The negative DEP (nDEP) force in the focusing part concentrates particles near the microchannel axis. The positive DEP (pDEP) force in the attractive area then absorbs particles into the internal chamber via electrodes. In general, the main advantage of the present design is the maximum trapping of incoming particles (with a trapping rate of over 95%) regardless of their initial location. In this study, numerical modeling was first done in three dimensions to sort and trap the microparticles. Then, a microchip was designed, built, and tested in a laboratory to validate the results and confirm the microfluidic system behavior. Finally, a parametric study was conducted to figure out the best voltage range of the electric fields in the microfluidic system. [Display omitted] • Maximize trapping of incoming particles regardless of initial location is the main advantage of the present design. • Use different electric fields operating at various frequencies for focusin g and trapping cells. • Use dual frequency in the microsystem is one of the main advantages of the present design. • The performance cartography is evaluated to determine the optimum parameters. • The proposed microchip is fabricated to validate the results. [ABSTRACT FROM AUTHOR]

[Display omitted] • A geometry study to enhance the enrichment in chips is proposed. • A new SLM with 1:1 DHE:TBP for simultaneous extraction of basic compounds of different polarity is presented. • The versatile semi-continuous device offers high sensitivity and good enrichments. • Good recoveries and excellent clean-up were obtained from human urine samples. Liquid-phase microextraction (LPME) in microfluidic devices involves extraction of acids or bases by diffusion in a pH gradient, from aqueous sample, through a supported liquid membrane (SLM), and into aqueous acceptor phase. The SLM is an integrated part of the device, and separates the donor (sample) and acceptor phase channels. In this work, the geometry of the donor and acceptor phase channels were studied and optimized. With optimal channel geometry (12 mm length, 2 mm width, 0.12 mm depth), metoprolol, haloperidol, nortriptyline, and loperamide were extracted from 900 μL urine and into 25 μL stagnant 10 mM HCl using a mixture of dihexyl ether and tributyl phosphate 1:1 v/v as the SLM. During 30 min of extraction, where the sample was pumped into the system at 30 μL min−1 and the acceptor phase was stagnant, recoveries exceeded 75 % and enrichment factors up to 28 were obtained. Evaluation of the analytical performance supported the reliability of the device in combination with HPLC-UV detection. Implementation of LPME in microfluidic devices is expected to increase in the future and the current paper provides experimental support for the importance of the careful design of the donor and acceptor channels. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate the feasibility of a carbohydrate–protein interaction analysis and reaction progress monitoring in microfluidic droplets using microscopic fluorescence measurements. The microdroplet Plexiglas ® chips are used to generate microdroplets of 0.3 nL at frequencies of 40 Hz. Fluorescence intensity and corrected fluorescence are measured under different experimental parameters such as concentration and composition of the biomolecules inside the droplets. They are used to detect carbohydrate–protein interactions in microdroplets using a model system of TRITC-labelled peanut agglutinin lectin (PNA) grafted onto the surface of polystyrene beads and galactose grafted onto the surface of FITC-polystyrene beads. These microchips could be used for the quantitative detection of galactose–PNA binding in microdroplets in direct assay formats with high specificity detection limits; in fact, we prove that non-specific lectins cannot form specific bindings. A binding assay for detecting galactose–complexes has been analyzed to study the binding and the parameters that influence the molecular association in a dynamic environment and results in a dissociation constant K D  = 0.07 mM. [ABSTRACT FROM AUTHOR]

Magnetic microflow cytometers integrate magnetic field sensors and microfluidic channels to detect cell suspensions labeled with magnetic beads. As the magnetic beads are superparamagnetic, commercial permanent magnets (PMs) are typiacally positioned bellow the microchip for an out-of-plane magnetization. Though, they require careful alignment as their magnetic field can impact the sensors sensitivity. In this paper, we overcome this drawback by presenting an innovative custom-made PM that notably combines high out-of-plane magnetic field (>100 mT) and low in-plane magnetic field (<1mT) over a large area (30.2mm2). This configuration qualifies the setup for simultaneous detection in multiple microfluidic channels within the same microchip, allowing parallel analysis of different cell samples or faster analysis of larger volumes of cell suspension. [ABSTRACT FROM AUTHOR]

Human luteinizing hormone (LH) is an important analyte for doping control analysis since it increases the athletic performance. However, traditional methods to detect LH have few disadvantages, such as long analysis duration, waste disposal problem and sample matrix effect. Addressing these problems, surface-enhanced Raman spectroscopy based LH analysis using a passive microfluidic chip was developed and optimized. Antibody modified magnetic gold nanoparticles captured the LH and then, 4-aminothiophenol (4-ATP) labeled nanoparticles formed the sandwich immunoassay structure. The complex and the other reactions occurred in different chambers of the chip. The SERS signals of 4-ATP were recorded from the chamber and the system was shown to detect 0.036 IU L −1 in serum samples. The performance of the immunoassay was compared to all other methods and the proposed assay was the fastest analysis of LH without any problems associated with the sensitivity. The shorter analysis time was recorded because the chip enables the control of all reactions in one place and there was no requirement of a specialized laboratory. [ABSTRACT FROM AUTHOR]

The research and applications of liquid chromatographic (LC) chips receive more and more attention due to the numerous advantages over the traditional and larger analytical systems, e.g. requirement for small sample and reagent volumes, fast and inexpensive analysis, dead-volume free connections and the ability to multiplex measurements. Since LC is one of the most powerful separation techniques, its miniaturization seems an obvious target of lab-on-a-chip developments. However, the common procedures used in the preparation of chromatographic columns are not well applicable at the microscopic level. Additionally, implementing sample injection of (sub)nanoliter volumes (with sensitive detection) is still a challenge. This review deals with microchips incorporating particle-based stationary phases and focuses on the lab-made and commercialized chromatographic separations discussing the particle retention methods, the designs/constructions of LC chips, the separation performances and possible applications. A survey about microfluidic chips - capable of efficient separations and high-throughput sample pretreatment - hyphenated with electrospray mass spectrometric devices to achieve sensitive detection has also been made. The merits and limitations of different commercial LC chips were compared with other published approaches, as well. [ABSTRACT FROM AUTHOR]

A new geometry for a versatile microfluidic-chip device based liquid phase microextraction was developed in order to enhance the preconcentration in microfluidic chips and also to enable double-flow and stopped-flow working modes. The microchip device was combined with a HPLC procedure for the simultaneous determination of two different families as model analytes, which were parabens and non-steroidal anti-inflammatories (NSAIDs): Ethyl 4-hydroxybenzoate (Et-P), Propyl 4-hydroxybenzoate (Pr-P), Butyl 4-hydroxybenzoate (Bu-P), IsoButyl 4-hydroxybenzoate (iBu-P), salycilic acid (SAC), ketoprofen (KET), naproxen (NAX), diclofenac (DIC) and ibuprofen (IBU) in urine samples. The new miniaturized microchip proposed in this work allows not only the possibility of working in double-flow conditions, but also under stagnant conditions (stopped-flow) (SF-μLPME). The sample (pH 1.5) was delivered to the SF-μLPME at 20 μL min −1 while keeping the acceptor phase (pH 11.75) under stagnant conditions during 20 min. The highest enrichment factors (between 16 and 47) were obtained under stopped-flow conditions at 20 μL min −1 (sample flow rate) after 20 min extraction; whereas the extraction efficiencies were within the range of 27–81% for all compounds. The procedure provided very low detection limits between 0.7 and 8.5 μg L −1 with a sample volume consumption of 400 μL. Parabens and NSAIDs have successfully been extracted from urine samples with excellent clean up and recoveries over 90% for all compounds. In parallel, the new device was also tested under double flow conditions, obtaining good but lower enrichment factors (between 9 and 20) and higher extraction efficiencies (between 45 and 95) after 7 min extraction, consuming a volume sample of 140 μL. The versatile device offered very high extraction efficiencies and good enrichment factor for double flow and stopped-flow conditions, respectively. In addition, this new miniaturized SF-μLPME device significantly reduced costs compared to the existing analytical techniques for sample preparation since this microchip require few microliters of sample and reagents and it is reusable. [ABSTRACT FROM AUTHOR]

Lab-on-Chip is currently considered the technology with the potential to revolutionize future biochemical analysis providing miniaturized, low-reagent volume microchips as an alternative to traditional benchtop analysis. Automated control of droplet flow is currently a key objective in microfluidics research, aiming for droplet logic microfluidic circuits. To this end, microfluidic research has been following the electronics paradigm, with several digital fluidic components being demonstrated towards the realization of digital fluidic circuits for automated liquid control and delivery. In this work, we introduce a new concept of microfluidic pressure controlled field-effect transistors (pFETs), towards droplet logic operations. Using a fluidic with porous and hydrophobic walls, the inherently pinned plug depins by pressure application through the porous wall (backpressure), thus enabling the actuation and the downward transportation of the plug due the action of gravity. This concept resembles the logic operation of a metal–oxide–semiconductor field-effect transistor (MOSFET). The pFET operating parameters are thus defined in a manner analogous to MOSFET digital switches and their dependence on the channel width is studied also for the first time. The successful operation of pFET devices for droplet logic operation is verified in continuous ON/OFF cycles, achieving OFF-ON and ON-OFF switching times under 1 s (0.864 s and 0.841 s respectively) and therefore promising rapid liquid switching times, comparable to electronic circuit ones. [ABSTRACT FROM AUTHOR]

The novel concept of a microfluidic chip with an integrated three-dimensional fractal geometry with nanopores, acting as a gas transport membrane, is presented. The method of engineering the 3D fractal structure is based on a combination of anisotropic etching of silicon and corner lithography. The permeation of oxygen and carbon dioxide through the fractal membrane is measured and validated theoretically. The results show high permeation flux due to low resistance to mass transfer because of the hierarchical branched structure of the fractals, and the high number of the apertures. This approach offers an advantage of high surface to volume ratio and pores in the range of nanometers. The obtained results show that the gas permeation through the nanonozzles in the form of fractal geometry is remarkably enhanced in comparison to the commonly-used polydimethylsiloxane (PDMS) densemembrane. The developed chip is envisioned as an interesting alternative for gas-liquid contactors that require harsh conditions, such as microreactors or microdevices, for energy applications. [ABSTRACT FROM AUTHOR]

Microfluidic biochips are replacing the conventional biochemical analyzers integrating the necessary functions on-chip. We are interested in flow-based biochips, where a continuous flow of liquid is manipulated using integrated microvalves, controlled from external pressure sources via off-chip control pins. Recent research has addressed the physical design of such biochips. However, such research has so far ignored the pin-count, which rises with the increase in the number of microvalves. Given a biochip architecture and a biochemical application, we propose an algorithm for reducing the number of control pins required to run the application. The proposed algorithm has been evaluated on several biochips, including the AquaFlux biochip from Microfluidic Innovations LLC. [ABSTRACT FROM AUTHOR]

Microfluidics researchers are increasingly using computer simulation in many different aspects of their research. However, these simulations are often computationally intensive: simulating the behavior of a simple microfluidic chip can take hours to complete on typical computing hardware, and even powerful workstations can lack the computational capabilities needed to simulate more complex chips. This slows the development of new microfluidic chips for new applications. To address this issue, we present a microfluidic simulation method that can simulate the behavior of fluids and particles in some typical microfluidic chips instantaneously (in around one second). Our method decomposes the chip into its primary components: channels and intersections. The behavior of fluid in each channel is determined by leveraging analogies with electronic circuits, and the behavior of fluid and particles in each intersection is determined by querying a database containing nearly 100,000 pre-simulated channel intersections. While constructing this database takes a nontrivial amount of computation time, once built, this database can be queried to determine the behavior of fluids and particles in a given intersection in a fraction of a second. Using this approach, the behavior of a microfluidic chip can be simulated in just one second on a standard laptop computer, without any noticeable degradation in the accuracy of the simulation. While our current technique has some constraints on the designs of the chips it can simulate (namely, T- or cross-shaped intersections, 90 degree channel turns, a fixed channel width, fluid flow rates between 0 and 2 cm/s, and particles with diameters between 1 and 20 microns), we provide several strategies for increasing the range of possible chip designs that can be simulated using our technique. As a proof of concept, we show that our simulation method can instantaneously simulate the paths followed by particles in both simple and complex microfluidic chips, with results that are essentially indistinguishable from simulations that took hours or even days to complete using conventional approaches. [ABSTRACT FROM AUTHOR]

Microfluidic capacitive sensors with enhanced performance and wireless sensing capability present great advantages for various pressure sensor applications. In this work, a liquid dielectric layer (LDL)-based wireless capacitive sensor for high sensitivity and low-pressure detection has been demonstrated. The wireless capacitive sensor was designed based on an LC resonant circuit model and integrated into a microfluidic device by introducing liquid-metal Galinstan into polydimethylsiloxane (PDMS) microchannels. The effect of various dielectric mediums (air, deionized (DI) water, and saline) on the performance of the capacitive sensor was characterized to study the sensitivity and robustness of the devices. Moreover, the high permittivity of liquid dielectric mediums enhances the sensitivity of the pressure sensor. The sensitivities of 0.0043 kPa−1, 0.0111 kPa−1, and 0.0125 kPa−1 were achieved for air, DI water, and saline-based dielectric mediums, respectively, for a low-pressure region of 0–10 kPa. Furthermore, we fabricated the wireless pressure sensor in three different form factors to enhance the applicability of the flexible wireless sensor. We also demonstrated the possibility of wirelessly monitoring human motion through real-time pressure detection using capacitive sensors fabricated with a liquid dielectric medium. The proposed LDL-based capacitive sensor, with high sensitivity, could be a potential candidate for low-pressure sensor applications, especially in detecting subtle pressure from the human body. [Display omitted] • Fabrication of liquid dielectric layer (LDL)-based microfluidic capacitive sensors. • Air, DI water, and saline were used as dielectric mediums. • High permittivity of liquid dielectric mediums enhances the sensitivity of the pressure sensor. • Human motion monitoring using LDL-based wireless capacitive sensors. [ABSTRACT FROM AUTHOR]

Recent progress in wettability-patterned microchips has facilitated the development of ultra-trace detection in multiple biomedical and food safety fields. The existence of a superhydrophilic trap can realize targeted deposition of the analyte. However, the wetting transition from the Cassie-Baxter state to the Wenzel state usually occurs during evaporation and leads to a larger deposition footprint, which has a strong impact on the detection sensitivity and uniformity. In this paper, we report an integrated design, fabrication, and evaporation strategy to avoid the transition for high-performance attomolar surface-enhanced Raman scattering (SERS) detection. An improved force balance model was proposed to design the microstructures of wettability-patterned microchips, which were fabricated by nanosecond laser direct writing and surface fluorination. The microchips were composed of superhydrophobic micro-grooves and superhydrophilic traps, by which the targeted deposition of Au nanoparticles and rhodamine 6G (R6G) onto a minimal area of ∼70 × 70 μm2 was realized after a two-step heated evaporation. Accordingly, the detection limit was down to the attomolar level (5 × 10−18 M) with SERS enhancement factors (EFs) exceeding 1010. More importantly, the Raman signals showed good uniformity (RSD of 11.5%) for the concentration of 2 × 10−17 M. A good linear relationship was obtained in the quantitative concentration range of 10−12 M to 5 × 10−18 M with a high correlation coefficient (R2) of 0.996. These wettability-patterned microchips exhibit high performance (that is, both good sensitivity and good uniformity) in the detection of ultra-trace molecules in aqueous solutions, avoiding the need for expensive equipment and considerable skill in operations. The proposed strategy could also be applied to other microfluidic devices for rapid and simple analyte pre-concentration. [Display omitted] • Micro-grooves were designed to avoid wetting transition during evaporation. • Wettability-patterned microchips were prepared by nanosecond laser in a simple way. • On-demand deposition of nanoparticles and analytes onto a minimal 70 × 70 μm2 area. • SERS detection limit down to attomolar level with a good uniformity (RSD = 11.5%). [ABSTRACT FROM AUTHOR]

One of the challenges in mathematical modelling of microchips is the lack of available data for dispersion coefficients of biomolecules. The main focus of this study was to determine the hydrodnamic dispersion coefficients of the model substrates, 4-Nitrophenyl-β- d -glucopyranoside (pNPG_1) and 4-Nitrophenyl-β- d -glucuronide (pNPG_2) for β-glucosidase and β-glucoronidase. The substrate solutions were pumped through the silica porous gel inside the S-shaped PDMS microreactor at flow rates of 1, 3 and 5 µl/min. The output flow was collected with respect to time and quantified by UPLC. The general mathematical model was derived for the coupled dynamics of convective–diffusive mass transfer and a computational algorithm was developed for the numerical solutions of the derived partial differential equations in MATLAB. The hydrodynamic dispersion coefficients of pNPG_1 were determined as 0.370 × 10 −6 , 3.638 × 10 −6 and 11.680 × 10 −6 m 2 /s, while as 0.368 × 10 −6 , 1.515 × 10 −6 and 3.503 × 10 −6 m 2 /s for pNPG_2 at respective flow rates. Furthermore, the relations between dispersion coefficients and flow rates were investigated. Obtained hydrodynamic dispersion coefficients can be used for modelling of pNPG reactions which may also be adapted to other enzyme related reactions within life sciences. [ABSTRACT FROM AUTHOR]

In microfluidics, a variety of platforms have emerged facilitating various physical effects for manipulating small volumes. Despite great functional diversity, most technologies are incapable of acting on direct feedback from the process liquid and instead require a sophisticated external control unit off-chip. Here, a microfluidic platform concept is demonstrated utilizing the volume phase transition of polymers via transistor-like components to actively switch between discrete fluid streams. Control is integrated at chip level for the first time, relying on information carried within the process liquid. Control commands are chemical signals such as solvent concentration, pH-value, or even salt. The developed logical modules can be interconnected independently through conclusive signal propagation, supporting an integrated circuit concept and large-scale integration. The approach enables the development of the basic logic gates (AND, OR, NOT) and their negated counterparts, as well as more sophisticated circuits such as an RS flip-flop and a chemofluidic oscillator. [ABSTRACT FROM AUTHOR]

Paper chip is an efficient and inexpensive device for pesticide residues detection. However, the reasons of detection error are not clear, which is the main problem to hinder the development of pesticide residues detection. This paper focuses on error analysis for pesticide detection performed on paper-based microfluidic chip devices, which test every possible factor to build the mathematical models for detection error. In the result, double-channel structure is selected as the optimal chip structure to reduce detection error effectively. The wavelength of 599.753 nm is chosen since it is the most sensitive detection wavelength to the variation of pesticide concentration. At last, the mathematical models of detection error for detection temperature and prepared time are concluded. This research lays a theory foundation on accurate pesticide residues detection based on paper-based microfluidic chip devices. [ABSTRACT FROM AUTHOR]

The emergence of microfluidic epithelial models using diverse types of cells within a physiologically relevant microenvironment has the potential to be a powerful tool for preclinical drug screening and pathophysiological studies. However, to date, few studies have reported the development of a complicated in vitro human nasal epithelial model. The aim of this study was to produce an in vitro human nasal mucosa model for reliable drug screening and clinical applications. Here, we integrated and optimized several culture conditions such as cell type, airway culture conditions, and hydrogel scaffolds into a microfluidic chip to construct an advanced in vitro human nasal mucosa model. We observed that the inducing factors for nasal gland-like structures were secreted from activated human dermal microvascular endothelial cells. Furthermore, our in vitro nasal mucosa presented different appearance and characteristics under hypoxic conditions. Morphological and functional similarities between in vivo nasal mucosa and our model indicated its utilization as a reliable research model for nasal diseases including allergic rhinitis, chronic sinusitis, and nasal polyposis. [ABSTRACT FROM AUTHOR]

We demonstrate a facile, plasma free process to fabricate both reversibly and irreversibly sealed microfluidic chips using a PDMS-based adhesive polymer mixture. This is a versatile method that is compatible with current PDMS microfluidics processes. It allows for easier fabrication of multilayer microfluidic devices and is compatible with micropatterning of proteins for cell culturing. When combined with our Shrinky-Dink microfluidic prototyping, complete microfluidic device fabrication can be performed without the need for any capital equipment, making microfluidics accessible to the classroom. [ABSTRACT FROM AUTHOR]

• Experimental results and observations are compared to an idealized simulation model. • Optimal deposition conditions for electroless plating in a microchannel are examined. • Low velocities are accompanied with hydrogen accumulations and extraneous deposition. • The deposition rate slows down for high electrolyte velocities towards turbulent flow. The trend of chip-packaging in the semiconductor industry is pointing towards 3D integrated circuits and scaling down to attain devices with enhanced efficiency and performance. To overcome the reassimilating challenges, we propose the usage of an electroless plated deposition layer to connect pillar bumps and create high-density interconnections. The substrates and pillar arrangements encompass our microchannel with the height of 50 µm or 25 µm where in between the electrolyte is forced with a superficial velocity of 0.3 to 300 mm s−1 in our experiments. The results are compared to a numerical multi-physics model which simulates idealized plating conditions without any disruptions to characterize and quantify the different flow regimes and undesired side-effects. In the low-velocity regime, hydrogen bubbles cannot be dislodged and remain in the microchannel which is accompanied with the formation of extraneous deposition on the resist surface. The mid-velocity regime shows a good match to the simulation model and is considered as optimal plating condition. The chemical reaction slows down for high velocities. [ABSTRACT FROM AUTHOR]

We present a new multi-nozzle electrospray emitter with integrated extraction electrode. Compared with existing multi-nozzle devices the electrospray process is supported by a nitrogen flow. Together with an integrated microfluidic system and the design of the electrode this leads to a compact system adapted to the specific needs of mass spectrometers which are on-line combined with a liquid chromatography system (LC-MS analysis). [ABSTRACT FROM AUTHOR]

In this study, we propose a degradation preventing sensing method for organic material in gas sensing application on polysilicon submicron wire (poly-Si SW) charge sensor chip. The poly-Si SW chip was fabricated by 0.35 μm two-polysilicon-four-metals (2P4 M) CMOS technology. The degradation of polymer material was reduced through the charge sensing mechanism. Compared with traditional sensing methods, there is no current flow through polymer based sensing film. Moreover, the lifetime, response variation and durability performance of sensor were improved. Based on CMOS technology, our poly-Si SW can be easily integrated with another system, i.e., wireless and microfluidic system. Therefore, this work also presents a good potential of poly-Si SW sensor chip to accomplish the goal of integrated multi-sensor in one low power consumption chip. This demonstration successfully shows organic sensing materials to accomplish the need in Internet of Things (IoT) applications [ABSTRACT FROM AUTHOR]