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Wearable systems for health monitoring are highly desired in personal diagnostics and precision medicine while challenges remain in constructing such wearable systems with reliability and high performance. Herein, we report a wearable platform for non-invasive monitoring biomarkers in sweat. The device is composed of a butterfly-shaped like microfluidic platform in which responsive photonic crystal hydrogels are embedded in each butterfly wing as sensors. Sweat lactate concentration and pH can be obtained via the color variation of the sensor with naked eyes. Accurate quantitative analysis of the two target analytes can be obtained via the image analysis on a mobile phone by integrating the linear range response to analytes within the physiological range. Moreover, the sensor exhibits good reproducibility, excellent selectivity and long-term stability. On-body trials have been conducted by attaching the device on volunteers' body, and the obtained results are consistent with those analyzed through standardized methods, demonstrating its potentiality in real-time and continuous monitoring sweat biomarkers. This non-invasive wearable sensor provides a new strategy for personal health monitoring and sports performance assessment. [Display omitted] • A wearable colorimetric sensor was developed for non-invasive sweat monitoring. • The device enables real-time sweat lactate and pH analysis. • The wearable device was based on photonic crystal hydrogel. • This wearable, low-cost and easy-to-operate technique holds potential for point-of-care detection. [ABSTRACT FROM AUTHOR]

Paper-based microfluidic analytical devices (μPADs) have become promising alternatives to clinical laboratory-based methods for point-of-care testing (POCT) of biomarkers in family care and resource-limited communities. Here, Co-doped carbon dots (Co-CDs) nanozyme with outstanding oxidase-mimicking catalytic activity and red fluorescent emission were prepared, and combined adhered-3D μPAD (A-3D μPAD) to monitor facilely alkaline phosphatase (ALP) level in whole blood samples. Co-CDs catalyzed the oxidization of nonfluorescent o -phenylenediamine (OPD) into 2,3-diaminophenazine (oxOPD) with yellow fluorescent emission due to the generation of tremendous O 2 •- species. With addition of ALP, ALP hydrolyzed l -ascorbic acid 2-phosphate into ascorbic acid, and the latter was oxidized by Co-CDs, then reacted with OPD to form blue fluorescent emission 3-(dihydroxyethyl)furo [3,4-b]quinoxaline-1-one (DFQ). Both DFQ and oxOPD quenched the fluorescence intensity of Co-CDs via inner-filter effect. The cascade reaction of ALP/Co-CDs was incorporated into A-3D μPAD based on above sensing principles. A-3D μPAD enabled sample pretreatment, cascade reaction and signal output, and integrated portable minimized device and smartphone for visual ALP detection. The linear range and limit of detection for ALP were 0.5–150 U L−1 and 0.1 U L−1, respectively, and the color varied from red, yellow to blue. The detection results for whole blood samples were consistent with biochemical detector. The efficiency, disposability, practicality and low-cost of A-3D μPAD can be extended to determine various biomarkers, and provided technical support for nanozyme applications in POCT environments. An efficiency, disposability, practicality and low-cost of A-3D μPAD platform was explored for sensitive and facile ALP detection in whole blood samples. [Display omitted] • Co-CDs nanozyme exhibited oxidase-like activity to oxidize OPD into oxOPD. • Co-CDs nanozyme with red fluorescent emission were applied for ALP assay. • Adhered-3D μPAD was fabricated by simple techniques of spraying pigment, loading reagents and adhering 2D μPAD. • ALP/Co-CDs cascade system was incorporated into adhered-3D μPAD for POCT of ALP activity. • This POCT platform displayed excellent performance to detect ALP level in whole blood sample. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) tumor microdevices are promising platform for biomimetic antitumor prediction and high-throughput chemotherapeutic screening and play crucial roles in the exploration of cancer-associated pharmaceutics and therapeutics. Traditional cell manipulation tools (e.g., non-adhesive surfaces and hanging drops) and recent microengineered systems (e.g., microfluidic chips and micropatterned array chips) have progressed in terms of microscale control, substantial tumor production, programmable drug combinations, and throughput analysis. However, establishing a facile 3D tumor microdevice to construct heterotypic tumor-microenvironmental profiles and for throughput, implementable, multi-instrument-compatible analysis of chemotherapies to advance consumer-grade tumor modelling tools is still being explored. In this study, we present a facilely operated tumor-on-a-chip platform for massive production of heterotypic 3D tumors and diverse investigations of combinatorial chemotherapy screening. Large quantity of heterotypic tumor generation with high geometric controllability (size difference: 19.6 μm) and operational repeatability (n = 10) was achieved using simple-to-fabricate micropatterned chips. Multiple characteristics of solid tumors, including phenotypic gradients (viability and proliferation) and heterogeneous cellular compositions (multi-cell participation and stroma composition), were reproduced in heterotypic tumors, being more biomimetic than homotypic tumors. We completed the user-friendly analytical evaluation of individual and combinatorial drug therapies, and demonstrated the high applicability of the platform in biomimetic tumor-related large-scale manipulation and on-chip analysis, as well as its high compatibility for off-chip detection. The entire operative process during tumor production and chemotherapy only requires the routine and easy-to-master pipetting manipulation. The establishment of a biomimetic and easy-to-use 3D tumor platform and the large-scale screening-like evaluation of combinatorial chemotherapies based on the usage of the micropatterned chip was achieved in a user-friendly manner. This advancement has significant application potential in the fields of oncology, drug discovery, and tissue engineering, and is expected to be valuable for developing accessible and generalizable tumor-on-a-chip microsystems for exploring cancer therapies. [Display omitted] • A heterotypic tumor-on-a-chip platform with facile operation. • Massive and repeatable production of size-uniform 3D tumors on micropatterned chips. • Multiple characteristics of solid tumors were reproduced in heterotypic tumors. • User-friendly on-chip and off-chip combinatorial chemotherapy investigations. [ABSTRACT FROM AUTHOR]

The integration of paper-based analytical devices with lab-on-a-chip technology has opened up new possibilities for miniaturized, rapid, low cost and portable diagnostic testing in resource limited settings. This work introduces an integrated lab-on-a-chip platform coupling paper-based analytical devices (LOC-PADs) for dual usage: electrochemically controlled solid-phase microextraction (EC-SPME) and determination of naproxen (NAP) by potentiometric ion-selective electrode (ISE) in biological samples. Conductive papers were successfully fabricated by a chemical procedure. Thereupon, a conducting molecularly imprinted polymer (CMIP) film based on PPy and an anionic model drug (NAP) as a template were applied to the conductive paper substrate via electrochemical methods. A microfluidic chip device was employed to assess the analytical performance of the fabricated paper-based CMIP. The designed chip is divided into two parts with a microfluidic channel between them. The first chamber is an extraction zone for EC-SPME of NAP by using the CMIP paper as a selective sorbent. The second chamber is the detection zone and consists of a paper-based NAP ion selective sensor for potentiometric detection of drug. The analytical process was investigated and optimized for each chamber. Remarkable selectivity towards NAP was achieved in the concentration range from 4.0 × 10−7 to 1.0 × 10−2 mol L−1 with determination coefficient (R2 = 0.99) and the limit of detection (LOD) was 2.0 × 10−7 mol L−1. Anionic Nernstian compliance was gained −58.5 ± 0.5 mV decade−1, and response time in the detection step was 7s for ISE. Satisfactory spiking recovery values within the acceptable range of 90–110 % with RSDs ≤7 % were achieved for the analysis of real samples with fully portable LOC device. The LOC-PADs were favorably used for selective extraction and determination of NAP in serum and saliva samples, respectively. EC-SPME caused sample clean-up, reduced or eliminated different interferences and enhanced selective response of ISE as detection zone of device. Integration of EC-SPME and ISE in a single chip enabled easy and fast determination of trace amounts of NAP in limited real sample volumes, and fully portable advantages. [Display omitted] • Paper based conducting molecularly imprinted polymer (CMIP) were synthesized electrochemically. • CMIP-papers were utilized in lab-on-a-chip device for dual application, clean-up & detection. • Selective responses were enhanced by integration of EC-SPME and ISE (EC-SPME- ISE). • Lab-on-a-chip EC-SPME-ISE enables detection of drug with the fully portable advantages. [ABSTRACT FROM AUTHOR]

Single cell mass spectrometry (scMS) has shown great promise for label free proteomics analysis recently. To present single cell samples for proteomics analysis by MS is not a trivial task. Existing methods rely on robotic liquid handlers to scale up sample preparation throughput. The cost associated with specialized equipment hinders the broad adoption of these workflows, and the sequential sample processing nature limits the ultimate throughput. In this work, we report a parallel sample processing workflow that can simultaneously process 10 single cells without the need of robotic liquid handlers for scMS. This method utilized 3D printed microfluidic devices to form reagent arrays on a glass slide, and a magnetic beads-based streamlined sample processing workflow to present peptides for LC-MS detection. We optimized key operational parameters of the method and demonstrated the quantification consistency among 10 parallel processed samples. Finally, the utility of the method in differentiating cell lines and studying the proteome change induced by drug treatment were demonstrated. The present method allows parallel sample processing for single cells without the need of expensive liquid handlers, which has great potential to further improve throughput and decrease the barrier for single cell proteomics. [Display omitted] • A parallel workflow for processing single cell samples for proteomics analysis. • Eliminate the need for high precision liquid handler. • Novel surface coating strategies to allow contact-based reagent transfer while minimizing sample loss on the surface. • Demonstrated proteomics analysis at single cell level with nanoLC-MS. [ABSTRACT FROM AUTHOR]

Accurately predicting durian maturity is a critically unresolved worldwide issue. Farmers currently determine durian ripeness based on their own observation and experience leading to inconsistencies in harvest timing. This reliance on human judgment often results in premature or overripe harvests, impacting fruit quality, yield, and market value. Existing technological solutions, such as sensors are often complex and require specialized expertise, hindering their adoption by farmers and consumers. Developing sensors that can accurately measure durian ripeness without damaging the fruit, are easy to use, and affordable remains a challenge. We introduce a microfluidic paper-based analytical device (μPAD) for on-site, safe matching to meet the demands of durian maturity evaluation. The μPAD automatically collected peduncle fluid without destroying the durian fruit for dual detection of total sugar and amino acid. For determining total sugar including sucrose, glucose, and fructose, several enzymatic steps were reduced to a single step of invertase for sucrose hydrolysis before total reducing sugar was measured using gold nanoparticle (AuNP) generation. Kinetics study of invertase on the μPAD showed V max and K m values of 1.42 mM min−1 and 2.17 mM, respectively, that agreed with the direct study of sucrose conversion. To increase device reliability, amino acid was also simultaneously measured with sugar using the simple ninhydrin test with the addition of SnCl 2. The developed sensor provided LODs of 3.50, 3.10, 3.30 μM, and 0.02 mg mL−1 for glucose, fructose, sucrose, and amino acid respectively. The μPADs were able to nondestructively discriminate between the mature and immature durians, showing high linear correlation with the standard dry weight method. The development of this μPAD technology has the potential to revolutionize durian cultivation practices, reduce post-harvest losses, and enhance the overall sustainability and profitability of the durian value chain, and can be further developed for maturity tests of other fruits. [Display omitted] • A user-friendly microfluidic paper-based device (μPAD) was introduced for on-site durian maturity evaluation. • The μPAD analyzed durian peduncle fluid, eliminating the need to damage the fruit itself. • The μPAD offered a single-step enzyme process to measure sugars and amino acids, simplifying traditional methods. • Kinetic study of invertase on paper substrate corresponded to the direct conversion of sucrose. • The μPAD accurately distinguished mature and immature durians, providing a reliable and affordable tool. [ABSTRACT FROM AUTHOR]

Optical detection is frequently performed on microfluidic chips for colorimetric analysis. Integrating liquid waveguide capillaries with total internal reflection with the microfluidic chip requires less procedures, which is suitable in the optical detection of microfluidic systems and is a practical alternative to increase the optical path length in the colorimetric assay of microfluidic devices for higher sensitivities and lower detection limit. However, this alternative has not been applied to the connection of PMMA chips or the microfluidic devices for the detection of phosphate in seawater. Here, a lab-on-a-chip system integrating a microfluidic chip and an external liquid waveguide capillary cell was presented to detect the phosphate in seawater. The detachable total internal reflection capillary made of Teflon AF 2400 connected to the chip transports sample and transmits light, greatly reducing detection limit, eliminating the interference from stray light and widening the dynamic range of the system without specific surface treatment of the microchannel. By utilizing an internal 5-cm absorption cell and an external 20-cm liquid waveguide capillary cell, the system reaches detection limits of 59 nM and 8 nM, respectively, and can detect phosphate concentration from 0 to 23 μM. An online analyzer was developed based on the high-sensitivity system and was applied to shipboard underway analysis for two scientific cruises and to laboratory measurements for seawater samples from Xisha sea area. Correlation analyses between the shipboard and laboratory phosphate measurements and other physical and biochemical elements revealed the marine ecological characteristics of the corresponding areas, demonstrating the high-sensitivity of this method over slight variations and narrow ranges of phosphate and the ability to provide microfluidic systems for high spatiotemporal resolution phosphate determination a practical and cost-effective alternative. [Display omitted] • First application of liquid waveguide capillary cell (LWCC) in microfluidic devices for seawater phosphate. • LOD for the phosphate using an external 20-cm LWCC is 8 nM, over 7 times the LOD using the 5-cm cell inside the PMMA chip. • Applications and analyses demonstrated the high-sensitivity method over slight variations and narrow ranges of phosphate. • Proposed method provides microfluidic systems for high-resolution determination a practical and cost-effective alternative. [ABSTRACT FROM AUTHOR]

Cell sorting is crucial in isolating specific cell populations. It enables detailed analysis of their functions and characteristics and plays a vital role in disease diagnosis, drug discovery, and regenerative medicine. Fluorescence-activated cell sorting (FACS) is considered the gold standard for high-speed single-cell sorting. However, its high cost, complex instrumentation, and lack of portability are significant limitations. Additionally, the high pressure and electric fields used in FACS can harm cell integrity. In this work, an acoustofluidic device was developed in combination with surface acoustic wave (SAW) and droplet microfluidics to isolate single-cell droplets with high purity while maintaining high cell viability. Human embryonic kidney cells, transfected with fluorescent reporter plasmids, were used to demonstrate the targeted droplet sorting containing single cells. The acoustofluidic sorter achieved a recovery rate of 81 % and an accuracy rate higher than 97 %. The device maintained a cell viability rate of 95 % and demonstrated repeatability over 20 consecutive trials without compromising efficiency, thus underscoring its reliability. Thermal image analysis revealed that the temperature of the interdigital transducer (IDT) during SAW operation remained within the permissible range for maintaining cell viability. The findings highlighted the sensitivity and effectiveness of the developed acoustofluidic device as a tool for single-cell sorting. The detachable microfluidic chip design enables the reusability of the expensive IDT, making it cost-effective and reducing the risk of cross-contamination between different biological samples. The results underscore its capability to accurately isolate individual cells on the basis of specific criteria, showcasing its potential to advance research and clinical applications requiring precise cell sorting methodologies. A new acoustofluidic device has been developed by integrating surface acoustic wave technology with droplet microfluidics to achieve high-purity isolation of single cells within droplets. This device comprises a disposable microfluidic chip and a reusable interdigital transducer. Utilizing this system, sorting of human embryonic kidney cells has been achieved with an impressive 81 % recovery rate and 97 % accuracy. [Display omitted] • Detachable microfluidic chip. • Reusable IDT. • Recovery rate of 81 %. • Accuracy higher than 97 %. • 95 % cell viability. [ABSTRACT FROM AUTHOR]

The rapid emergence of microfluidic paper-based devices as point-of-care testing (POCT) tools for early disease diagnosis and health monitoring, particularly in resource-limited areas, holds immense potential for enhancing healthcare accessibility. Leveraging the numerous advantages of paper, such as capillary-driven flow, porous structure, hydrophilic functional groups, biodegradability, cost-effectiveness, and flexibility, it has become a pivotal choice for microfluidic substrates. The repertoire of microfluidic paper-based devices includes one-dimensional lateral flow assays (1D LFAs), two-dimensional microfluidic paper-based analytical devices (2D μPADs), and three-dimensional (3D) μPADs. In this comprehensive review, we provide and examine crucial information related to paper substrates, design strategies, and detection methods in multi-dimensional microfluidic paper-based devices. We also investigate potential applications of microfluidic paper-based devices for detecting viruses, metabolites and hormones in non-invasive samples such as human saliva, sweat and urine. Additionally, we delve into capillary-driven flow alternative theoretical models of fluids within the paper to provide guidance. Finally, we critically examine the potential for future developments and address challenges for multi-dimensional microfluidic paper-based devices in advancing noninvasive early diagnosis and health monitoring. This article showcases their transformative impact on healthcare, paving the way for enhanced medical services worldwide. [Display omitted] • Structure design strategies for microfluidic paper-based analytical devices. • Sensing mechanism and application in noninvasive testing. • Theoretical models of capillary-driven fluids within paper. [ABSTRACT FROM AUTHOR]

Droplet microfluidics with push-pull and microdialysis sampling from brain slices, cultured cells and engineered tissues produce low volume mass limited samples containing analytes sampled from the extracellular space. This sampling approach coupled to mass spectrometry (MS) detection allows evaluation of time-dependent chemical changes. Our goal is an approach for continuous sampling and segregation of extracellular samples into picoliter droplets followed by the characterization of the droplets using nanoelectrospray ionization (nESI) MS. The main focus here is the optimization of the carrier oil for the microfluidic device that neither affects the stability of picoliter droplets nor compatibility with MS detection of a range of analytes. We developed and characterized a 1-octanol-assisted ultra-small volume droplet microfluidic nESI MS system for the analysis of neurotransmitters in distinct samples including cerebrospinal fluid (CSF). The use of a 1-octanol oil phase was effective for generation of aqueous droplets as small as 65 pL and enabled detection of acetylcholine (ACh) and gamma-aminobutyric acid (GABA) in water and artificial CSF. Continuous MS analysis of droplets for extended periods up to 220 min validated the long-term stability of droplet generation and analyte detection by nESI-MS. As an example, ACh response demonstrated a linear working range (R2 = 0.99) between 0.4 μM and 25 μM with a limit of detection of 370 nM (24 amol), enabling its quantitation in rodent CSF. The established droplet microfluidics – nESI MS approach allows the analysis of microenvironments at high spatiotemporal resolution. The approach may allow microsampling and monitoring of spatiotemporal dynamics of neurochemicals and drugs in the brain and spinal cord of live animals. [Display omitted] • A pL droplet microfluidic-nESI MS system optimized for neurotransmitter detection. • The 1-octanol oil phase effectively generates aqueous droplets as small as 65 pL. • Long-term stability for droplet generation and analyte detection by MS. • Acetylcholine quantified from rat cerebral spinal fluid samples. • Characteristics of the system designed for in vivo monitoring of neurotransmitters. [ABSTRACT FROM AUTHOR]

A proportion of Haematococcus pluvialis under the light stress can effectively conduct astaxanthin biosynthesis, leading to the increase in cell size. Although the size is a critical indicator for identifying the astaxanthin-rich H. pluvialis cells, the cut-off size to be separated varies from sample to sample. Here, we report an ultrastretchable, straight elasto-inertial microchannel with tunable separation threshold to continuously separate the light-induced H. pluvialis cells by size. The symmetrical sheath flows confine the particles to the channel sidewalls, and large particles can cross the interface of viscoelastic fluids to the equilibrium position at the channel centerline. By stretching the microfluidic chip, the medium-sized particles can gradually migrate to the channel centerline in the narrower and longer channel, bringing the tunable separation threshold. Results show that the separation performance of the ultrastretchable microfluidic device is affected by total flow rate, flow rate ratio of sheath to sample, polyethylene oxide (PEO) solution configuration. Lastly, size-tunable separation of light-induced H. pluvialis cells is demonstrated. To the best of our knowledge, this is the first report on cell migration in co-flow configurations in the ultra-stretchable microfluidics. Separation of H. pluvialis is not only a relevant end application in harvesting the astaxanthin-rich species, but the separated populations of highly productive microalgal cells will open a venue for cellular directed evolution. [Display omitted] • The tunable particle and cell migration in the ultrastretchable, sheath-flow-assisted elasto-inertial microchannel is revealed. • This is the first report on cell migration in co-flow configurations in the ultra-stretchable microfluidics. • This method can select desirable microalgal cells and also provides a reliable route for directed evolution of cells. [ABSTRACT FROM AUTHOR]

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]

The global prevalence of diabetes mellitus, a serious chronic disease with fatal consequences for millions annually, is of utmost concern. The development of efficient and simple devices for monitoring glucose levels is of utmost significance in managing diabetes. The advancement of nanotechnology has resulted in the indispensable utilization of advanced nanomaterials in high-performance glucose sensors. Modulating the morphology and intricate composition of transition metals represents a viable approach to exploit their structure/function correlation, thereby achieving optimal electrocatalytic performance of the synthesized catalysts. Herein, a sensitive and rapid Cu-encapsulated Cu 2 S@nitrogen-doped carbon (Cu@Cu 2 S@N–C) hollow nanocubes-functionalized microfluidic paper-based analytical device (μ-PAD) was fabricated. Through a delicate sacrificial template/interface technique and thermal decomposition, inter-connected hollow networks were formed to boost the active sites, and the carbon shell was coated to protect Cu from being oxidation. For application, the constructed μ-PAD is used for glucose sensing utilizing an origami automated sample pretreatment system enabled by a simple application of strong alkaline solution on wax paper. Under optimal circumstances, the Cu@Cu 2 S@N–C electrochemical biosensor exhibits broad detection range of 2–7500 μM (R2 = 0.996) with low detection limit of 0.16 μM (S/N = 3) and high sensitivity of 1996 μA mM−1 cm−2. Additionally, the constructed μ-PAD also exhibited excellent selectivity, stability, and reproducibility. By rationally designing the double-shell hollow nanostructure and introducing Cu-encapsulated inner layer, the synthesized Cu@Cu 2 S@N–C hollow nanocubes show large specific surface area, short diffusion channels, and high stability. The proposed origami μ-PAD has been successfully applied to serum samples without any additional sample preparation steps for glucose determination, offering a new perspective for early nonenzymatic glucose diagnosis. [Display omitted] • Cu@Cu 2 S@N–C hollow nanocubes-based origami μ-PAD sensor was fabricated. • Cu@Cu 2 S@N–C hollow nanocubes possessed large specific surface area and high stability. • Cu@Cu 2 S@N–C hollow nanocubes exhibited excellent electrocatalytic performance for glucose. • The proposed sensor was applied for glucose detection without any additional sample preparation steps. [ABSTRACT FROM AUTHOR]

Separation, classification, and focusing of microparticles are essential issues in microfluidic devices that can be implemented in two categories: using labeling and label-free methods. Label-free methods differentiate microparticles based on their inherent properties, including size, density, shape, electrical conductivity/permittivity, and magnetic susceptibility. Dielectrophoresis is an advantageous label-free technique for this objective. Besides, centrifugal microfluidic devices exploit centrifugal forces to move liquid and particles. The simultaneous combination of dielectrophoretic and centrifugal forces exerted on microparticles still needs to be scrutinized more to predict their trajectories in such devices. An integrated system utilizing two categories in microfluidics is proposed: dielectrophoretic manipulation of microparticles and centrifugal-driven microfluidics, followed by a numerical analysis. In this regard, we assumed a rectangular microchannel with internal unilateral planar electrodes equipped with three equal-sized outlets placed radially on a centrifugal platform where microparticles flow toward the disc's outer edge. The effect of different coordinate-based parameters, including radial and lateral distances (X and Y offsets)/tilting angles toward the radius direction (α), on the particles' movement was investigated. Additionally, the effect of operational parameters, including applied voltage, the microchannel width, the number of enabled electrodes, the diameter of particles, and the configuration of electrodes, were analyzed, and the distributions of particles toward the outlets were monitored. It was found that enhanced particle focusing becomes possible at lower rotation speeds and higher electric field values. Furthermore, the proposed centrifugal-DEP system's efficiency for classifying red blood cells/platelets and Live/Dead yeast cells systems was evaluated. Our integrated system is introduced as a novel method for focusing and classifying various microparticles with no need for sheath flows, having the ability to conduct particles at desired routes and focusing width. Furthermore, the system effectively separates various bioparticles and offers ease of operation and high-efficiency throughput over conventional dielectrophoretic devices. [Display omitted] • A centrifugal-DEP device for various applications including biomedical engineering and diagnostics is proposed. • The proposed system can be prepared using regular methods, making it attractive for further experimental studies. • The proposed centrifugal-DEP device provides advantages over the conventional SpinDEP device. • Live and Dead yeast cells have been separated using a 1 MHz, 5 V electric field at a 70 rad/s rotating speed. • A mixture of RBCs and Platelets was successfully classified at 100 rad/s rotation speed and 15 V electrical potential. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a prevalent neurodegenerative disease with no effective treatment. Efficient and rapid detection plays a crucial role in mitigating and managing AD progression. Deep learning-assisted smartphone-based microfluidic paper analysis devices (μPADs) offer the advantages of low cost, good sensitivity, and rapid detection, providing a strategic pathway to address large-scale disease screening in resource-limited areas. However, existing smartphone-based detection platforms usually rely on large devices or cloud servers for data transfer and processing. Additionally, the implementation of automated colorimetric enzyme-linked immunoassay (c-ELISA) on μPADs can further facilitate the realization of smartphone μPADs platforms for efficient disease detection. This paper introduces a new deep learning-assisted offline smartphone platform for early AD screening, offering rapid disease detection in low-resource areas. The proposed platform features a simple mechanical rotating structure controlled by a smartphone, enabling fully automated c-ELISA on μPADs. Our platform successfully applied sandwich c-ELISA for detecting the β-amyloid peptide 1–42 (Aβ 1–42, a crucial AD biomarker) and demonstrated its efficacy in 38 artificial plasma samples (healthy: 19, unhealthy: 19, N = 6). Moreover, we employed the YOLOv5 deep learning model and achieved an impressive 97 % accuracy on a dataset of 1824 images, which is 10.16 % higher than the traditional method of curve-fitting results. The trained YOLOv5 model was seamlessly integrated into the smartphone using the NCNN (Tencent's Neural Network Inference Framework), enabling deep learning-assisted offline detection. A user-friendly smartphone application was developed to control the entire process, realizing a streamlined "samples in, answers out" approach. This deep learning-assisted, low-cost, user-friendly, highly stable, and rapid-response automated offline smartphone-based detection platform represents a good advancement in point-of-care testing (POCT). Moreover, our platform provides a feasible approach for efficient AD detection by examining the level of Aβ 1–42, particularly in areas with low resources and limited communication infrastructure. The schematic diagram of the overview of an offline deep learning-assisted smartphone-based paper-based microfluidic platform for screening of Alzheimer's disease. [Display omitted] • Deep learning-assisted smartphone-based platform enables offline detection. • Fully automated microfluidic paper analysis devices (μPADs). • Smartphone-based platform for detection of biomarker of Alzheimer's disease. [ABSTRACT FROM AUTHOR]

This study reports a new electrochemical method for tryptamine determination using a paper-based microfluidic device and a thermoplastic electrode (TPE) as an amperometric detector. Tryptamine (Tryp) is a biogenic amine present in drinks and foods. Even though this compound has some beneficial effects on human health, the ingestion of foods with high concentrations of Tryp may be detrimental, which justifies the need for monitoring the Tryp levels. The TPEs were made from 50% carbon black and 50% polycaprolactone and characterized by cyclic voltammetry, demonstrating enhancement in the analytical response compared to other carbon composites. TPEs also showed a better antifouling effect for Tryp compared to conventional glassy carbon electrodes. Once characterized, the electrodes were incorporated into the microfluidic device to determine Tryp in water and cheese samples using amperometry. A linear range was achieved from 10 to 75 μmol L−1 with limits of detection and quantification of 3.2 and 10.5 μmol L−1, respectively. Therefore, this work shows promising findings of the electrochemical determination of Tryp, bringing valuable results regarding the electrochemical properties of thermoplastic composites. Image 1 • Fouling resistant thermoplastic electrodes (TPEs) for tryptamine determination. • 50% carbon black and 50% polycaprolactone were used to prepare the electrodes. • TPE-μPAD can ensure fast analyses and generate less waste. • Possibility of reusing the electrodes by simply polishing them after several uses. • A simple strategy to eliminate ascorbic acid interference. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS) is a key technology for sensitive and high-resolution mass analysis of peptides and proteins. Sample clean-up and chromatographic separation is typically performed prior to MS analysis to limit adduct formation and ionization suppression. Usually, this requires a high-pressure LC pump system equipped with expensive metal chromatographic columns placed in-line of an electrospray ionization (ESI) source. Microfluidic devices coupled to MS have gained considerable attention, due to the promise of low manufacturing costs, low sample consumption and channels with a high surface area to volume ratio and tailorable functional groups. Here, we describe a thiol-ene microfluidic chip capable of fast chromatographic sample clean-up, concentration, and separation of complex protein and peptide mixtures with direct on-chip ESI. On-chip reversed-phase chromatography (RPC) was performed through an in-situ polymerized monolith frit for retaining inexpensive commercially available reversed-phase (RP) spherical particles, while on-chip ESI is achieved through an emitter monolithically implemented by precision micro milling. The on-chip integration of both RPC and ESI emitter allowed for a minimization of dead-volumes and enables very fast sample clean-up, efficient ionization, and mass analysis of peptides and proteins from complex matrices. Image 1 • All thiol-ene microfluidic chip for fast chromatography and MS analysis of peptides and proteins. • In-situ polymerized monolith frit allows packing of reversed-phase chromatography (RPC) materials for on-chip separation. • Precision micro milling of a monolithically implemented emitter allows on-chip ESI. • On-chip integration of RPC and ESI enables fast sample clean-up/concentration and efficient MS of peptides and proteins from complex matrices. [ABSTRACT FROM AUTHOR]

Microfluidics offer novel and state-of-the-art pathways to process materials. Microfluidic systems drastically reduce timeframes and costs associated with traditional lab-scale efforts in the area of analytical sample preparations. The challenge arises in effectively connecting microfluidics to off-chip analysis tools to accurately characterize samples after treatment on-chip. Fabrication of a chip-to-world connection includes one end of a fused silica capillary interfaced to the outlet of a microfluidic device (MFD). The other end of the capillary is connected to a commercially available CEI-100 interface that passes samples into an inductively coupled plasma mass spectrometer (ICP-MS). This coupling creates an inexpensive and simple chip-to-world connection that enables on-chip and off-chip methods of analyzing the separation of rare earth elements. Specifically, this is demonstrated by utilizing isotachophoresis (ITP) on a microfluidic chip to separate up to 14 lanthanides from a homogenous sample into elementally pure bands. The separated analyte zones are successfully transferred across a 7 nL void volume at the microchip-capillary junction, such that separation resolution is maintained and even increased through the interface and into the ICP-MS, where the elemental composition of the sample is analyzed. Lanthanide samples of varying composition are detected using ICP-MS, demonstrating this versatile and cost-effective approach, which maintains the separation quality achieved on the MFD. This simple connection enables fast, low-cost sample preparation immediately prior to injection into an ICP-MS or other analytical instrument. Image 1 • Fourteen non-radioactive lanthanides are separated in a serpentine microchannel using isotachophoresis. • Separation quality is maintained across a ninety-degree turn in a microchannel. • Separation is transferred from a microfluidic device into an ICP-MS via a low-cost capillary transition. [ABSTRACT FROM AUTHOR]

In this survey, a reliable and applicable Y–Y shaped micro–channel in a microfluidic device was designed and manufactured. A number of micro–scaled hedges were precisely fabricated inside the micro–channel to facilitate the immobilization of synthesized core–shell Fe 3 O 4 @SiO 2 magnetic nanoparticles (MNPs), functionalized by triethoxyphenylsilane (TEPS) by sol-gel technique. Both sample and reagents were introduced into the microfluidic device by a syringe pump to perform the extraction and desorption steps. The functionalized MNPs were characterized by transmission electron microscopy, X-ray diffraction spectroscopy and Fourier transform infrared spectroscopy. By adopting the strategy of extraction–on–chip using this microfluidic device, we were benefited from implementing the entire analyses with the minimum amount of desorbing solvent, MNPs, and aqueous/fruit juice samples. In contrast to dispersive solid phase extraction, dispersion of MNPs during experiment is prevented by fabrication of micro-scaled hedges in the micro-channel. Consequently the stabilized MNPs are reused for the entire runs. The microfluidic device was successfully exploited as an efficient extracting plateau to evaluate the extraction/desorption capability in analysis of some organophosphorus pesticides (OPPs) as model compounds. Our results indicate that the functionalization of Fe 3 O 4 @SiO 2 with TEPS, improved their extraction capability due to the existence of phenyl and hydroxyl groups for more efficient π–π and hydrogen bonding interactions. Eventually, μL-scale of the organic solvent was injected into a gas chromatography–mass spectrometry system. The limits of detection (3S b) and quantification (10S b) for the OPPs were 0.03–0.1 and 0.1–0.35 ng mL−1, respectively. In addition, the interday and intraday precisions were lower than 5.3% (n = 3). The obtained recovery was 95–99% for water samples and 88–96% for fruit juice samples while satisfactory regression coefficients of 0.9949–0.9991, could be achieved. • A Y–Y shape micro–channel in a microfluidic device was fabricated. • The micro-channel consists equally spaced micro-scale hedges. • Core–shell Fe 3 O 4 @SiO 2 magnetic nanoparticles were synthesized as extractive phases. • The nanoparticles were firmly retained by the hedges and external magnet. [ABSTRACT FROM AUTHOR]

Micro total analytical systems (μTAS) are attractive to multiple fields that include chemistry, medicine and engineering due to their portability, low power usage, potential for automation, and low sample and reagent consumption, which in turn results in low waste generation. The development of fully-functional μTAS is an iterative process, based on the design, fabrication and testing of multiple prototype microdevices. Typically, microfabrication protocols require a week or more of highly-skilled personnel time in high-maintenance cleanroom facilities, which makes this iterative process cost-prohibitive in many locations worldwide. Rapid-prototyping tools, in conjunction with the use of polydimethylsiloxane (PDMS), enable rapid development of microfluidic structures at lower costs, circumventing these issues in conventional microfabrication techniques. Multiple rapid-prototyping methods to fabricate PDMS-based microfluidic devices have been demonstrated in literature since the advent of soft-lithography in 1998; each method has its unique advantages and drawbacks. Here, we present a tutorial discussing current rapid-prototyping techniques to fabricate PDMS-based microdevices, including soft-lithography, print-and-peel and scaffolding techniques, among other methods, specifically comparing resolution of the features, fabrication processes and associated costs for each technique. We also present thoughts and insights towards each step of the iterative microfabrication process, from design to testing, to improve the development of fully-functional PDMS-based microfluidic devices at faster rates and lower costs. Image 1 • An introduction in PDMS chemistry, surface modification and curing strategies is shown. • A critical evaluation of rapid-prototyping tools for PDMS-based microfluidic devices fabrication is made. • General strategies on the combination of fabrication tools and methods to meet users' requirements are presented. • A comparison among microfabrication methods is made, in terms of feature resolution, cost and fabrication time. [ABSTRACT FROM AUTHOR]

Accumulating evidence suggests that the features associated with epithelial to mesenchymal transition (EMT) in circulating tumor cells (CTCs) reflect intrinsic metastatic potential and associate with therapy resistance. Thus, profiling the EMT phenotypes of CTCs is increasingly important for cancer diagnosis and prediction of therapeutic responses. However, rapid assessment of the EMT status of a global CTC population is still a challenge due to the difficulty in enriching and phenotyping CTCs simultaneously. Here, we report a microfluidic device consisting of an enrichment section and a capture section for differential capture of rare tumor cells from blood according to their EMT phenotypes. A row of micropillars was constructed in the enrichment section to provide cross-flows for the size-dependent filtration of cells. Thus, MCF-7 and MDA-MB-231 tumor cells mimicking CTCs were first separated from white blood cells through the micropillars and continually flowed into the capture section at a reduced velocity under a differential hydrodynamic pressure. In the capture section, the heterogeneous tumor cells were then phenotypically sorted and captured in two cascaded compartments functionalized with either an anti-EpCAM antibody or a cocktail of antibodies against mesenchymal markers including Axl, PD-L1, and EGFR. Direct counting of the captured cells in each compartment resulted in the enumeration of epithelial and mesenchymal subpopulations of the tumor cells without additional labeling. Furthermore, the captured tumor cells were successfully maintained for up to six days in the device with high viability and marked proliferation for downstream analysis. Thus, this integrated microfluidic device may have great potential in phenotyping EMT status of CTCs for precision cancer therapy. Image 1 • A microfluidic device for simultaneously enriching, capturing, and phenotyping epithelial and mesenchymal rare tumor cells. • A special channel topology allows high sample throughput and slow flow rate for immunocapturing. • Regional immunocapturing ensures recognizing and separating phenotypically heterogeneous tumor cells. • A novel triple-antibody cocktail enables specifically capturing mesenchymal tumor cells. [ABSTRACT FROM AUTHOR]

Herein, some (modified) paper–based substrates were prepared and utilized as extractive phases in a microfluidic device and their extraction performances examined for analytes with different polarities. Reagents including hexadecyltrimethoxysilane (HDTMS), phenyltrimethoxysilane (PTES), (3-aminopropyl) triethoxysilane (APTES) and 3–(2,3–epoxypropoxy) propyltrimethoxysilane (EPPTMOS) were implemented for the modification process. Due to the induction of different silane functional groups, it was anticipated to have various interactions for the tested analytes. Eventually, the prepared paper sheets were used as extractive phases for solid–phase extraction within a microfluidic system. The microfluidic setup not only improves the mechanical stability of the paper–based phases but also facilitated the mass transfer process and decreases the energy consumption. The selected analytes contained antidepressant drugs, organophosphates and triazine toxins, having different structures and polarities. Afterward, the existing interactions between the paper–based sorbents and the selected analytes were investigated by Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA) for data analysis. According to the obtained data, the PTES modified surface paper was selected for quantitative investigation and optimization. The major parameters associated with the extraction performance were studied. A linear range was obtained for amitriptyline and trimipramine, 0.05–200 μg L−1, and the calibration graph for clomipramine was linear in the range of 0.02–200 μg L−1. The employment of microfluidic device in conjunction with gas chromatography-mass spectrometry led to the limits of detections of 0.005–0.01 μgL−1 for the antidepressant drugs. The relative recoveries for the tested drugs in urine samples were in the range of 95–103%. Image 1 • Modified paper extractive phases were prepared and used in a microfluidic device. • Different modification reagents were used to induce various functionalities. • The microfluidic setup facilitates mass transfer and improves the efficiency. • The interactions impacts were investigated by PCA and HCA. • Trace levels of some antidepressant drugs were detected in urine samples. [ABSTRACT FROM AUTHOR]

Aptamer based microfluidic platforms have been developed rapidly in recent years, and strategies to improve detection sensitivities of such platforms have attracted a significant amount of attention. To achieve whole cell sensitive detections by microfluidic devices, a new dual-rolling circle amplification (RCA) detection approach is presented in this study. This dual-RCA approach includes a capturing RCA (cRCA) reaction that is designed to modify microfluidic channel surfaces with long tandem repeating aptamers (i.e. poly-aptamers) to effectively capture target E. coli O157:H7 cells. We demonstrate that this poly-aptamers modified microchannels capture 3-fold more target cells in comparison with microchannels modified with mono-aptamers against the target cells. In addition, signalling RCA (sRCA) is employed in the dual-RCA design to further enhance detection signals. Our results show that the detection signals are enhanced by up to 50 times by sRCA when compared with those with single fluorescence probes. Furthermore, by combing both the cRCA and the sRCA in one dual-RCA detection system, we demonstrate that the detection signals can be significantly enhanced by ∼250-fold. We also show that E. coli O157:H7 detections with the dual-RCA approach can be used in different food matrices, including orange juice and milk where the limit of detection of 80 cells/mL is achieved. In conclusion, this microfluidic device in combination with a dual-RCA to enhance both target capturing and detection signals is a simple and promising approach to sensitive whole-cell detections for food safety inspections. Image 1 • A novel dual-RCA whole cell detection system is developed for rapid and sensitive detection applications using microfluidic devices. • A cRCA can significantly enhance target capturing, and a sRCA can significantly amplify detection signals. • The dual-RCA increases overall detection signal intensities by approximately 250 times when compared with detections without RCAs. • The dual-RCA whole cell detection achieves an excellent LOD of 80 cell/mL. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) as a potentially powerful analytical platform have recently gained significant attention for on-site monitoring of heavy metal ions, which are one of the most significant environmental concern because of non-degradability and high toxicity. The commonly applied μPADs suffers from some defects, such as heterogeneous deposition of reagent, resulting in poor detection limits and low sensitivity. So, in this work, a three-dimensional origami μPAD combined with PVC Membrane was developed, which can manage problems of movement of colored products or leaching out the dye and leading to color heterogeneity in the detection zones. Furthermore, a waste layer was added to μPAD for loading of more amounts of the analyte, which results in improvement of detection limit. As a proof of concept, the μPAD was used for the analysis of Cu2+ ion. For this purpose, pyrocatechol violet and chrome azurol S as colorimetric reagents were doped into PVC membrane and injected in the detection zone. The proposed μPAD was presented good linearity in the ranges of 5.0–1400.0 and 5.0–200.0 mg L−1, and the limits of detections of 1.7 and 1.9 mg L−1 in presence of chrome azurol S and pyrocatechol violet, respectively. Image 1 • Development of a new design of paper-based microfluidic device for heavy metal ions. • PVC doping of indicators prevents leaching out the dye and fix it on the paper. • The μPADs combined with PVC immobilization shows higher sensitivity. • Presence of waste layer into μPAD allows loading of more amounts of analyte.. [ABSTRACT FROM AUTHOR]

Porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome-coronavirus (SADS-CoV) are three emerging and re-emerging coronaviruses (CoVs). Symptoms caused by these three viruses are extremely similar, including acute diarrhea, vomiting and even death in piglets. To date, strict biosecurity is still the most effective disease prevention and control measures, and the early detection of pathogens is the most important link. Here, we developed a microfluidic-RT-LAMP chip detection system for the first time, which could detected PEDV, PDCoV and SADS-CoV simultaneously, and had advantages of rapid, simple, sensitive, high-throughput, and accurate at point-of-care settings. The lowest detection limits of the microfluidic-RT-LAMP chip method are 101 copies/μL, 102 copies/μL and 102 copies/μL for PEDV, PDCoV and SADS-CoV, respectively. The whole detection procedure can be finished rapidly in 40 min without any cross-reaction with other common swine viruses. A total of 173 clinical swine fecal samples characterized with diarrheal symptoms were used to evaluate the performance of the newly developed system, which presented good stabilities (C.V.s<5%) and specificities (100%), and possessed sensitivities of 92.24%, 92.19% and 91.23% for PEDV, PDCoV and SADS-CoV respectively. In summary, the established microfluidic-RT-LAMP chip detection system could satisfy the demanding in field diagnoses, which was suitable for promotion in remote areas due to its fast, portable and cost-effective characters. Image 1 • Microfluidic chip and LAMP were firstly integrated for high-throughput and multitarget detection of PEDV, PDCoV and SADS-CoV. • The microfluidic-RT-LAMP chip system established greatly facilitated the rapid diagnosis of the PEDV, PDCoV and SADS-CoV. • The microfluidic chip device provides excellent prospects in swine enteric coronaviruses surveillance for remote areas. [ABSTRACT FROM AUTHOR]

Microfluidics has revolutionized the fields of bioanalytical chemistry, cellular biology, and molecular biology. Advancements in microfluidic technologies, however, are often limited by labor, time, and resource-intensive fabrication methods, most commonly a form of photolithography. The advent of 3D printing has helped researchers fabricate proof-of-concept microfluidics more rapidly and at lower costs but suffers from poor resolution and tedious post-processing to remove uncured resin from enclosed channels. Additionally, custom resins and printers are often needed to create entirely enclosed channels, which increases cost and complexity of fabrication. In this work we demonstrate the ability to create microfluidic devices by covalently sealing 3D-printed parts with open-faced channels to polydimethylsiloxane (PDMS). Open-faced channels are easier to print than fully enclosed channels and can be printed using an inexpensive and commercially available stereolithography 3D printer and resin. The 3D-printed parts are sealed to PDMS, a common substrate used in traditional microfluidic fabrication, using two different techniques. The first involves coating the part with a commercially available silicone spray before sealing to PDMS via plasma treatment. In the second technique, the cured methacrylate resin is silanized with (3-Aminopropyl)triethoxysilane (APTES) before binding to PDMS with plasma treatment. Both methods create a strong seal between the two substrates, which is demonstrated with several types of microfluidic devices including droplet and gradient generators. Image 1 • 3D-printed parts are sealed to poly(dimethylsiloxane) to create microfluidic devices. • 3D-printed parts are silanized before sealing to PDMS. • Two sealing methods are presented for rapid prototyping of microfluidics. • Fabrication techniques are simple and rapid compared to traditional methods. [ABSTRACT FROM AUTHOR]

Nowadays, great efforts are made in developing new technology for rapid detection of specific DNA sequences, for environmental monitoring, forensic analysis and rapid biomedical diagnosis applications. Microfluidic paper-based analytical devices are suitable platforms for the development of point of care devices, due to their simple fabrication protocols, ease of use and low cost. Herein, a methodology for in situ detection of single strand DNA by using a colorimetric assay based on the formation of a DNAzyme within a paper substrate was developed. A DNAzyme that could only be formed in the presence of a specific sequence of the Y human amelogenin gene was designed. The performance of the DNAzyme was followed colorimetrically first in solution and then in paper substrates. The reaction was found to be specific to the Y fragment selected as analyte. The DNAzyme reaction on paper enabled the unequivocal colorimetric identification of the Y single strand DNA fragment both qualitatively, with the naked eye (143 ng), and quantitatively by image analysis (45.7 ng). As a proof of concept, a microfluidic paper-based device, pre-loaded with all DNAzyme reagents, was characterized and implemented for the simultaneous detection of X and Y single strand DNA fragments. Image 1 • Optimized methodology for in situ DNA detection in a paper device format. • Detection based on a DNAzyme using Y human amelogenin fragment. • Presents a non-enzymatic, colorimetric and rapid way to detect DNA sequences. • Detection: quantitatively by calculating the grey intensity values. • Detection: qualitatively by the presence of a green color "coffee ring". [ABSTRACT FROM AUTHOR]

Cancer metastasis, that cancer cells migrate from primary to distance site, is the major cause of death for cancer patients. Investigation of the correlation between cell migration and extracellular stimulation is critical to develop effective therapy for suppressing cancer metastasis. However, the existing cell migration assays remain limitations to faithfully investigate cell migration capability. In this work, a microfluidic device embedded with impedance measurement system was developed for the quantification of cancer cell migration process. Cancer cells were guided and migrated along a Matrigel-filled microchannel mimicking the basement membrane. The microchannel was embedded with 5 pairs of opposite electrodes. Cell migration process was monitored by impedance measurement and migration speed was calculated from the traveling distance divided by the time taken. Impedimetric quantification of cell migration under extracellular stimulation of interleukin-6 was demonstrated. The result showed a higher measurement sensitivity compared to the conventional Transwell assay. The current microfluidic device provides a reliable and quantitative assessment of cellular response under tested conditions. It is potentially beneficial to the study of suppressing cancer metastasis. Image 1 • Impedimetric quantification of migration speed of cells migrating in a Matrigel-filled microchannel. • Successful measurement of cells suspended in 3D environment. • Quantification of the migration capability of Hela and Huh-7 cells. • Demonstration of migration speed measurement of IL-6 cytokine stimulated cells. • Higher measurement sensitivity compared to the conventional Transwell assay. [ABSTRACT FROM AUTHOR]

This study reports, for the first time, the possibility to manufacture analytical devices on polyester substrates using a cutting printer. The protocol involves the design of a layout in a graphical software, the cut into polyester films and the lamination against one or multiple polyester films coated with a thermosensitive layer. The feasibility of the proposed approach was demonstrated through the fabrication of 96-microwell plates, 3D microfluidic mixing and distance-based microfluidic devices. The printer has enabled cutting microchannels wider than 300 μm on polyester films and a thickness of 250 μm. Urea and glucose assays were performed on microwell plates aiming for their quantification in artificial urine and serum samples. The presented results revealed good agreement with the expected values. The complexation reaction between Fe2+ and o -phenanthroline was selected as model to investigate the feasibility of the 3D mixing device. Absorbance measurements were recorded for the reaction product performed in both on and off -chip modes. Considering the achieved data, the on -chip mixing exhibited similar behavior when compared to off -chip reaction, thus demonstrating to be efficient to perform mixtures due to the turbulence generated inside three-dimensional channels. Lastly, a distance-based device was designed to detect H 2 O 2 based on the displacement of a dye plug promoted by the oxygen generation using a copper-modified paper sheet. The distance-based peroxymeter revealed a linear behavior in the concentration range between 1 and 5% (v/v) and a LOD equal to 0.5% (65.2 mM). Based on the results herein reported, the proposed method represents a simple and alternative protocol to produce microdevices, using affordable and inexpensive raw materials, within 10 min, and at a cost lower than US$ 0.10 per unit. Image 1 • A cutting printer was explored to produce analytical devices on polyester films. • The fabrication protocol was able to create microchannels wider than 300 μm. • Microwell plate, 3D mixing and distance-based devices were successfully presented. • The unit cost of the proposed device was estimated to be cheaper than US$ 0.10. • The polymeric devices revealed great potential for bioanalytical applications. [ABSTRACT FROM AUTHOR]

We present a facile sample partitioning method to enable rapid and low-cost digital PCR (dPCR) assays. By subdividing a high percentage of the sample volume into a large number of equal volume compartments with a self-digitization (SD) chip, this method can achieve a low-waste and high-order sample discretization in a matter of minutes. The SD chip contains a set of parallel microfluidic channels used for sample delivery, and each channel is connected with two rows of cylindrical wells to hold the discretized sample. By utilizing a degassed PDMS sealing slab as a detachable vacuum pumping source, the SD chip automatically generate large arrays of small sample volumes without requirement of external pumping and valving components. Unlike most microfluidic chamber-based methods for sample discretization, our detachable SD chip allows for discretizing sample with air flushing, then peeling off the cover PDMS slab and sealing the digitized samples with oil layer. Due to obviation of time-consuming oil flushing, such microfluidic device can achieve much faster digitization of sample volumes. Furthermore, this digitization chip can partition more than 90% of a sample volume, which is important for the applications where the amount of material available is small. We also demonstrated the utility of the proposed SD chip by applying it to a dPCR assay. Image 1 • A facile and fast sample digitization (SD) method is developed. • Air flushing is used for the fast removal of the excess sample. • A low sample waste is achieved by combining closed waste chambers and capillary valves. • Our SD chip can provide low-cost and precise quantitative nucleic acid assays. [ABSTRACT FROM AUTHOR]

Paper-based microfluidic device was designed with wax-printing to combine potentiometric, fluorimetric and colorimetric detection zones. This newly developed trimodal paper chip has been used for on-site determination of ketamine hydrochloride (KET) as a date rape drug in beverages. The device employed polyaniline nano-dispersion as conducting polymer in ion sensing paper electrodes designed to fit USB plug connector. Carbon dots-gold nanoparticles and cobalt thiocyanate were used in fluorescence and color detection zones, respectively. Cellular phone's camera facilitated the on-site fluorimetric and color detection. The implemented trimodal detection system exhibited specificity for KET detection in the presence of several other beverage interferences i.e., biogenic amines. This innovative sensor brings together analytical figures of merit for effective KET detection in single aliquot of spiked beverages. The proposed paper-based chip also fulfils WHO criteria for point-of-care devices posing the proposed trimodal paper device as an active part for rapid, on-site drug diagnostics and to be applied further for other similar drugs. Image 1 • Potentiometric, fluorimetric and colorimetric sensors are developed for Ketamine detection. • The trimodal detection system is fabricated on a paper-based device. • Facile detection with USB plug and UV torch with mobile phone camera. • The microfluidic device is compared favorably to WHO criteria for point-of-care. [ABSTRACT FROM AUTHOR]

Microfluidic and capillary devices are increasingly being used in analytical applications while their overall size keeps decreasing. Detection sensitivity for these microdevices gains more importance as device sizes and consequently, sample volumes, decrease. This paper reviews optical, electrochemical, electrical, and mass spectrometric detection methods that are applicable to capillary scale and microfluidic devices, with brief introduction to the principles in each case. Much of this is considered in the context of separations. We do consider theoretical aspects of separations by open tubular liquid chromatography, arguably the most potentially fertile area of separations that has been left fallow largely because of lack of scale-appropriate detection methods. We also examine the theoretical basis of zone electrophoretic separations. Optical detection methods discussed include UV/Vis absorbance, fluorescence, chemiluminescence and refractometry. Amperometry is essentially the only electrochemical detection method used in microsystems. Suppressed conductance and especially contactless conductivity (admittance) detection are in wide use for the detection of ionic analytes. Microfluidic devices, integrated to various mass spectrometers, including ESI-MS, APCI-MS, and MALDI-MS are discussed. We consider the advantages and disadvantages of each detection method and compare the best reported limits of detection in as uniform a format as the available information allows. While this review pays more attention to recent developments, our primary focus has been on the novelty and ingenuity of the approach, regardless of when it was first proposed, as long as it can be potentially relevant to miniature platforms. [Display omitted] • Covers open and packed capillary HPLC, capillary and μchip electrophoretic platforms. • Optical, Electrochemical and mass spectrometric detection. • Recent coverage on applications but includes classic groundbreaking articles. • Provides a detailed tabulation of topical reviews in last 12 years. • Provides attainable and typical limits of detection for most approaches. [ABSTRACT FROM AUTHOR]

Small endosome-derived lipid nanovesicles (30–200 nm) are actively secreted by living cells and serve as pivotal biomarkers for early cancer diagnosis. However, the study of extracellular vesicles (EVs) requires isolation and purification from various body fluids. Although traditional EVs isolation and detection technologies are mature, they usually require large amount of sample, consumes long-time, and have relatively low-throughput. How to efficiently isolate, purify and detect these structurally specific EVs from body fluids with high-throughput remains a great challenge in in vitro diagnostics and clinical research. Herein, we suggest a nanosized microfluidic device for efficient and economical EVs filtration based on an alumina nanochannel array membrane. We evaluated the filtration device performance of alumina membranes with different diameters and found that an optimized chamber array with a hydrophilic-treated channel diameter of 90 nm could realize a filtration efficiency of up to 82% without any assistance from chemical or physical separation methods. Importantly, by integrating meticulously designed multichannel microfluidic biochips, EVs can be captured in-situ and monitored by antibody barcode biochip. The proposed filtration chip together with the high-throughput detection chip were capable of filtration of a few tens of μL samples and recognition of different phonotypes. The practical filtration and detection of EVs from clinical samples demonstrated the high performance of the device. Overall, this work provides a cost-effective, highly efficient and automated EVs filtration chip and detection dual-function integrated chip platform, which can directly separate EVs from serum or cerebrospinal fluid with an efficiency of 82% and conduct in-situ detection. This small fluidic device can provide a powerful tool for highly efficient identifying and analyzing EVs, presenting great application potential in clinical detection. Microfluidic device for EVs separating based on alumina nanochannel array membrane was developed, achieving EVs separation efficiency up to 82%. The separation chip is integrated with well-designed detection chip to form dual function platform. This work provides low-cost, time-saving and automated universal platform for EVs separation and characterization, which will have great potential in vitro diagnostics and clinical researches. [Display omitted] • The EVs filtration device achieves filtration efficient 82% and speed 1.5 mL/h per chip. • EVs detection chip can be integrated onto the filtration device forming all-in-one system. • The experiments of different sample prove the excellent performance of integrated apparatus. [ABSTRACT FROM AUTHOR]

Digital polymerase chain reaction (digital PCR) is an important quantitative nucleic acid analysis method in both life science research and clinical diagnostics. One important hypothesis is that by physically constraining a single nucleic acid molecule in a small volume, the relative concentration can be increased therefore further improving the analysis performance, and this is commonly defined as the confinement effect in digital PCR. However, experimental investigation of this confinement effect can be challenging since it requires a microfluidic device that can generate partitions of different volumes and an instrument that can monitor the kinetics of amplification. (96). Here, we developed a real-time digital PCR system with a multivolume droplet array SlipChip (Muda-SlipChip) that can generate droplet of 125 nL, 25 nL, 5 nL, and 1 nL by a simple "load-slip" operation. In the digital region, by reducing the volume, the relative concentration is increased, the amplification kinetic can be accelerated, and the time to reach the fluorescence threshold, or Cq value, can be reduced. When the copy number per well is much higher than one, the relative concentration is independent of the partition volume, thus the amplification kinetics are similar in different volume partitions. This system is not limited to studying the kinetics of digital nucleic acid amplification, it can also extend the dynamic range of the digital nucleic acid analysis by additional three orders of magnitude by combining a digital and an analog quantification algorithm. (140). In this study, we experimentally investigated for the first time the confinement effect in the community of digital PCR via a new real-time digital PCR system with a multivolume droplet array SlipChip (Muda-SlipChip). And a wider dynamic range of quantification methods compared to conventional digital PCR was validated by this system. This system provides emerging opportunities for life science research and clinical diagnostics. (63). [Display omitted] • A real-time digital PCR system with a multivolume droplet array SlipChip was developed. • Experimental investigation of the confinement effect was demonstrated. • A wide dynamic range of digital quantification method was developed. [ABSTRACT FROM AUTHOR]

Cellular biomechanics plays a significant role in the regulation of cellular physiological and pathological processes. In recent years, multiple methods have been developed to evaluate cellular biomechanics, such as atomic force microscopy (AFM), micropipette aspiration, and magnetic tweezers. However, most of these methods only focus on a single parameter and cannot automate the process at a high-efficiency level. A novel microfluidic method is necessary to achieve the simultaneous multi-parametric measurement of cellular biomechanics and high-precision cellular mechanical phenotyping at high throughput. To tackle the issue concerning the low-throughput and cellular single-parameter evaluation, we designed and fabricated a microfluidic chip featuring multiple micro-constrained channels structure, providing a simultaneous multi-parametric assessment of cellular biomechanics, including elastic modulus, recovery capability, and deformability. We compared the biomechanical properties of normal human gastric mucosal epithelial cells (GES-1) and human gastric cancer cells (AGS and MKN-45) by the chip. Results demonstrated that the elastic modulus of GES-1, AGS, and MKN-45 cells decreased sequentially, which was the opposite of their invasiveness and metastasis potential, suggesting the inverse correlation between cellular elastic modulus and malignancy. Meanwhile, the recovery capability and deformability of GES-1, AGS, and MKN-45 cells increased sequentially, demonstrating the positive correlation between cellular deformability and malignancy. Furthermore, multiple parameters were used to distinguish gastric cancer cells from normal gastric cells via machine learning. An accuracy of over 94.8% for identifying gastric cancer cells was achieved. This study provides a deep insight into the biophysical mechanism of gastric cancer metastasis at the single-cell level and possesses great potential to function as a valuable tool for single-cell analysis, thereby facilitating high-precision and high-throughput discrimination of cellular phenotypes that are not easily discernible through single-marker analysis. [Display omitted] • A novel microfluidic chip to assess multi-parametric cellular mechanical properties. • Precise cellular deformation model of gastric adenocarcinoma cells crossing physiological barriers. • High-precision mechanical phenotype of gastric cells based on cellular biomechanics via machine learning. • A deep insight into gastric cancer metastasis and great potential to function as a distinctive cellular biomarker. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD), one of the most prevalent neurodegenerative diseases, results in severe cognitive decline and irreversible memory loss. Early detection of AD is significant to patients for personalized intervention since effective cure and treatment methods for AD are still lacking. Despite the severity of the disease, existing highly sensitive AD detection methods, including neuroimaging and brain deposit-positive lesion tests, are not suitable for screening purposes due to their high cost and complicated operation. Therefore, these methods are unsuitable for early detection, especially in low-resource settings. Although regular paper-based microfluidics are cost-efficient for AD detection, they are restricted by a poor limit of detection (LOD). To address the above limitations, we report the ultrasensitive and low-cost nanocellulose paper (nanopaper)-based analytical microfluidic devices (NanoPADs) for detecting one of the promising AD blood biomarkers (glial fibrillary acidic protein, GFAP) using Surface-enhanced Raman scattering (SERS) immunoassay. Nanopaper offers advantages as a SERS substrate, such as an ultrasmooth surface, high optical transparency, and tunable chemical properties. We detected the target GFAP in artificial serum, achieving a LOD of 150 fg mL-1. The developed NanoPADs are distinguished by their cost-efficiency and ease of implementation, presenting a promising avenue for effective early detection of AD's GFAP biomarker with ultrahigh sensitivity. More importantly, our work provides the experimental routes for SERS-based immunoassay of biomarkers on NanoPADs for various diseases in the future. Ultrasensitive SERS-Based Immunoassay NanoPADs for Early Detection of AD. [Display omitted] • Ultrasensitive and low-cost detection of biomarker of Alzheimer's disease. • Nanocellulose-paper-based biosensing microfluidic devices. • Surface-enhanced Raman scattering immunoassay of GFAP. [ABSTRACT FROM AUTHOR]

3D printing has revolutionized the manufacturing process of microanalytical devices by enabling the automated production of customized objects. This technology promises to become a fundamental tool, accelerating investigations in critical areas of health, food, and environmental sciences. This microfabrication technology can be easily disseminated among users to produce further and provide analytical data to an interconnected network towards the Internet of Things, as 3D printers enable automated, reproducible, low-cost, and easy fabrication of microanalytical devices in a single step. New functional materials are being investigated for one-step fabrication of highly complex 3D printed parts using photocurable resins. However, they are not yet widely used to fabricate microfluidic devices. This is likely the critical step towards easy and automated fabrication of sophisticated, complex, and functional 3D-printed microchips. Accordingly, this review covers recent advances in the development of 3D-printed microfluidic devices for point-of-care (POC) or bioanalytical applications such as nucleic acid amplification assays, immunoassays, cell and biomarker analysis and organs-on-a-chip. Finally, we discuss the future implications of this technology and highlight the challenges in researching and developing appropriate materials and manufacturing techniques to enable the production of 3D-printed microfluidic analytical devices in a single step. [Display omitted] • 3D printing technology is a trend in manufacturing microfluidic devices. • Advances in bioanalytical applications on 3D-printed microfluidic devices are presented. • A comparison of the advantages and disadvantages of major 3D printing methods was addressed. • The Internet of Things can help users to potentiate 3D printing technology. • Challenges and future impact of 3D printing in bioanalytical research are discussed. [ABSTRACT FROM AUTHOR]

Preterm birth (PTB) is a leading cause of neonatal mortality, such that the need for a rapid and accurate assessment for PTB risk is critical. Here, we developed a 3D printed microfluidic system that integrated solid-phase extraction (SPE) and microchip electrophoresis (μCE) of PTB biomarkers, enabling the combination of biomarker enrichment and labeling with μCE separation and fluorescence detection. Reversed-phase SPE monoliths were photopolymerized in 3D printed devices. Microvalves in the device directed sample between the SPE monolith and the injection cross-channel in the serpentine μCE channel. Successful on-chip preconcentration, labeling and μCE separation of four PTB-related polypeptides were demonstrated in these integrated microfluidic devices. We further show the ability of these devices to handle complex sample matrices through the successful analysis of labeled PTB biomarkers spiked into maternal blood serum. The detection limit was 7 nM for the PTB biomarker, corticotropin releasing factor, in 3D printed SPE-μCE integrated devices. This work represents the first successful demonstration of integration of SPE and μCE separation of disease-linked biomarkers in 3D printed microfluidic devices. These studies open up promising possibilities for rapid bioanalysis of medically relevant analytes. [Display omitted] • 3D printed microfluidic solid-phase extraction/microchip electrophoresis devices. • On-chip fluorescent labeling and microchip electrophoresis shown for biomarkers. • Lower sample concentrations can be analyzed using on-chip preparation. • On-chip processing yields better separations for complex sample matrices. [ABSTRACT FROM AUTHOR]

Microfluidic techniques have emerged as powerful tools in single-cell research, facilitating the exploration of omics information from individual cells. Cell morphology is crucial for gene expression and physiological processes. However, there is currently a lack of integrated analysis of morphology and single-cell omics information. A critical challenge remains: what platform technologies are the best option to decode omics data of cells that are complex in morphology and size? This review highlights achievements in microfluidic-based single-cell omics and isolation of cells based on morphology, along with other cell sorting methods based on physical characteristics. Various microfluidic platforms for single-cell isolation are systematically presented, showcasing their diversity and adaptability. The discussion focuses on microfluidic devices tailored to the distinct single-cell isolation requirements in plants and animals, emphasizing the significance of considering cell morphology and cell size in optimizing single-cell omics strategies. Simultaneously, it explores the application of microfluidic single-cell sorting technologies to single-cell sequencing, aiming to effectively integrate information about cell shape and size. The novelty lies in presenting a comprehensive overview of recent accomplishments in microfluidic-based single-cell omics, emphasizing the integration of different microfluidic platforms and their implications for cell morphology-based isolation. By underscoring the pivotal role of the specialized morphology of different cells in single-cell research, this review provides robust support for delving deeper into the exploration of single-cell omics data. [Display omitted] • Microfluidic devices enhance precision and efficiency in single-cell omics. • Diverse platforms allow morphological integration for single-cell isolation. • Current sorting techniques need refining to fully capture cell morphology data. [ABSTRACT FROM AUTHOR]

Droplet microfluidics has the ability to greatly increase the throughput of screening and sorting of enzymes by carrying reagents in picoliter droplets flowing in inert oils. It was found with the use of a specific surfactant, the interfacial tension of droplets can be very sensitive to droplet pH. This enables the sorting of droplets of different pH when confined droplets encounter a microfabricated trench. The device can be extended to sort enzymes, as a large number of enzymatic reactions lead to the production of an acidic or basic product and a concurrent change in solution pH. The progress of an enzymatic reaction is tracked from the position of a flowing train of droplets. We demonstrate the sorting of esterase isoenzymes based on their enzymatic activity. This label-free technology, that we dub droplet sorting by interfacial tension (SIFT), requires no active components and would have applications for enzyme sorting in high-throughput applications that include enzyme screening and directed evolution of enzymes. Image 1 • A novel droplet microfluidic device allows the sorting of droplets based on pH without the use of labels or active components. • The technique is used to view the progression of an enzyme reaction via the flow position of droplets. • The device is used to sort droplets containing esterase isoenzymes based on their enzymatic activity. [ABSTRACT FROM AUTHOR]

This article reviews the research contributions along the past five years concerning to monolithic materials for the development of affinity-based sorbents in the field of microextraction techniques. The first part of this paper includes an introduction regarding monolithic affinity media and information of different binding agents (such as immunoglobulin-binding proteins, enzymes, lectins, antibodies, aptamers, dyes and immobilized metal ions and nanoparticles, among others) that can act as affinity ligands. Then, the preparation of monoliths and ligand immobilization strategies as well as the different available formats (syringes, pipette tips, spin columns, capillaries, disks and microfluidic devices) for their use in micro-solid phase extraction are mentioned. On the basis of the binding agents used to prepare affinity monolithic-based sorbents, the last part of manuscript includes several analytical and preparative applications of these monoliths for sample preparation covering different fields (analytical chemistry, biotechnology, proteomics, etc.). Current trends and possible future directions of these affinity-based sorbents in sample preparation are also given. Image 1 • Affinity-based monoliths for extraction of biomacromolecules were reviewed. • The synthesis to enhance selective extraction in affinity materials is debated. • The preparation of affinity materials in microextraction formats were highlighted. • The current challenges and the future perspectives of this field were examined. [ABSTRACT FROM AUTHOR]

Most of the on-site approaches for inferring of the post-mortem interval are still based on observative data from the direct body inspection, whereas, objective and quantitative analyses, such as potassium in the vitreous humor, are require laboratory instrumentation and skilled personnel. The present paper presents a simple and low cost analytical method suitable for use at the crime scene for inferring the time since death. The method uses a microfluidic paper-based device (μPAD) for the determination of ammonium in the vitreous humor (VH) based on the selective interaction between the ammonium and the Nessler's reagent. The color change was measured in terms of "RGB distance" by using a simple and free smartphone application. The optimized device showed a limit of detection of 0.4 mmol L−1, with between days precision less than 9.3% expressed as relative standard deviation, and accuracy between days from 94.5% to 104.5%. The selectivity of the Nessler's reaction was tested towards the main vitreous humor compounds, and no significant interferences were found. This paper-based analytical device was successfully used for the determination of ammonium ion in VH samples from forensic autopsies. The results obtained with the proposed method, although for a limited number of cases (n = 25), showed a close correlation with the data obtained with an instrumental analysis based on capillary electrophoresis. Moreover, in order to make the evaluation of results as simple as possible, a direct correlation between the color intensity, expressed as RGB distance, and the post-mortem interval was studied and a significant correlation was found (R2 > 0.78). In conclusion, the present preliminary study showes that the proposed device could be an additional tool to the traditional methods for a more accurate, although still presumptive, estimation of the time of death directly at the crime scene. Image 1 • A simple and low cost analytical method suitable for use at the crime scene for inferring the time since death is presented. • The device uses the microfluidic paper-based technology and the selectivity of the Nessler's reagent towards ammonium ion. • A concordance between the results obtained with the proposed procedure and those using CE-UV is proved. • The proposed procedure showed significant advantages for thanatochemical analysis at the crime scene. [ABSTRACT FROM AUTHOR]

Field-amplified stacking (FAS) is a commonly used method for enhancing the sensitivity of charged species from low conductive media in capillary electrophoresis. FAS also showed significant sensitivity enhancement effect on a uniform paper fluidic channel by proper design of the electrolyte. In this paper, a novel method of introducing electric field gradient is proposed by geometry design of a 2D paper fluidic channel, and field amplification effect was successfully demonstrated with reduced requirement on the sample's conductivity. Sensitive colorimetric detection of microalbuminuria (MAU) from urine samples was demonstrated by mobile phone camera. Experimental results showed that, with active electric field motivation, up to 93.5% of the loaded protein probe could be effectively transferred and stacked into a narrow band on the newly designed paper fluidic channel. A limit of detection (LOD) of 6.5 mg‧L−1 HSA was achieved with a dynamic range of 10–300 mg‧L−1 (linear in the range of 10–100 mg‧L−1, R2 = 0.991). Combined with selective staining of albumin with bromophenol blue (BPB), the established method was applied to the detection of MAU from clinical urine samples, and consistent results with that of the clinical method were obtained. With this paper-based analytical device (PAD), MAU from highly conductive urine samples can be directly loaded and detected without any pretreatment. This method provides a way to develop highly sensitive point-of-care test (POCT) for rapid screening of some diseases. Image 1 • Novel field amplification achieved mainly by the change of paper channel geometry, rather than the conductivity difference. • Protein probe was actively transported with a high transfer rate up to 93.5%, vs. less than 50% only by capillary force. • Sensitivity was enhanced by 2 orders of magnitude as demonstrated by colorimetric detection of human serum albumin (HSA). • Detection of microalbuminuria (MAU) from clinical urine samples was successfully demonstrated. [ABSTRACT FROM AUTHOR]

Early diagnosis of cancer by biomarker detection has been widely studied since it can lead to an increase in patient survival rates. Magnetic nanoparticles (MNPs) play an important role in this field acting as a valuable tool in the biomarker immunocapture and detection. In this work, Co 0.25 Zn 0.75 Fe 2 O 4 (CoZnFeONPs) nanoparticles were synthesized and applied as enzyme mimics of peroxidase-like catalysis in a disposable enzyme-free microfluidic immunoarray device (μID). The catalytic activity of CoZnFeONPs was evaluated by hydrogen peroxide detection using cyclic voltammetry and the apparent Michaelis-Menten constant was estimated by Lineweaver–Burk equation showing good K m values. In μID, the immunosensors were assembled with monoclonal antibody against CYFRA 21-1 covalently immobilized on graphene oxide previously deposited on the screen-printed carbon-based electrodes. Under optimized conditions, the method presented a good linear response for CYFRA 21-1 in the range of 3.9–1000 fg mL−1 achieving an ultralow limit of detection (LOD) of 0.19 fg mL−1. For comparison, Fe 3 O 4 nanoparticles (FeONPs) was also synthetized and presented results slight inferior to that obtained with CoZnFeONPs. The methods developed using both MNPs exhibited countless advantages when compared with the immunosensors developed for CYFRA-21-1, previously reported in the literature. The methods were successful applied for the detection of CYFRA 21-1 in real serum samples of healthy and prostate cancer patients and showed good correlation with results obtained with the enzyme-linked immunosorbent assay (ELISA). The CoZnFeONPs associated with the disposable microfluidic immunoarray device provides a simple and effective method for biomarker detection that could satisfy the need for a low-cost and rapid test for early diagnosis of cancer. Image 1 • The synthetized Co 0.25 Zn 0.75 Fe 2 O 4 (CoZnFeONPs) were used for the first time for biomarker detection. • CoZnFeONPs nanoparticles were synthesized and applied as enzyme mimics of peroxidase. • The low-cost disposable enzyme-free device were successfully applied for detection of CYFRA 21-1 in patient samples. [ABSTRACT FROM AUTHOR]

This study describes for the first time the development of 3D printed microfluidic devices with integrated electrodes for label-free counting of E. coli cells incorporated inside droplets based on capacitively coupled contactless conductivity detection (C4D). Microfluidic devices were fully fabricated by 3D printing in the T-junction shape containing two channels for disperse and continuous phases and two sensing electrodes for C4D measurements. The disperse phase containing E. coli K12 cells and the continuous phase containing oil and 1% Span® 80 were pumped through flow rates fixed at 5 and 60 μL min−1, respectively. The droplets with incorporated cells were monitored in the C4D system applying a 500-kHz sinusoidal wave with 1 V pp amplitude. The generated droplets exhibited a spherical shape with average diameter of 321 ± 9 μm and presented volume of 17.3 ± 0.5 nL. The proposed approach demonstrated ability to detect E. coli cells in the concentration range between 86.5 and 8650 CFU droplet−1. The number of cells per droplet was quantified through the plate counting method and revealed a good agreement with the Poisson distribution. The limit of detection achieved for counting E. coli cells was 63.66 CFU droplet−1. The label-free counting method has offered instrumental simplicity, low cost, high sensitivity and compatibility to be integrated on single microfluidic platforms entirely fabricated by 3D printing, thus opening new possibilities of applications in microbiology. Image 1 • The label-free counting of E. coli cells inside droplets generated on microfluidic devices has been proposed. • Microfluidic devices with integrated sensing electrodes were entirely fabricated by 3D printing. • E. coli cells were successfully detected by contactless conductivity measurements. • The proposed method provided limit of detection of 63.66 CFU droplet−1. • The label-free counting method offered instrumental simplicity, low cost, and high sensitivity. [ABSTRACT FROM AUTHOR]

Polymerase Chain Reaction (PCR) is an important and prevalent technique in biotechnology because of its crucial role in cloning DNA fragments and diagnostic applications. In the present study, a high-throughput two-phase PCR device is designed and fabricated which utilizes a serpentine microchannel together with a spiral structure. The former is for the droplet-generation and mixing and the latter is for the thermal cycling process. Moreover, the effect of diamond nanoparticles (diamondNP) on the performance of PCR is also investigated while using commercial PCR devices and the fabricated PCR device designed in this study. Using numerical simulation, it is shown that within the simple and easy-to-make microchannel structures designed in this study, there are different transient secondary flows which can help mixing the contents of the droplets including PCR solution and diamondNP. Moreover, a new fabrication process is used for the design of the droplet-generation chip which is applicable for the fabrication of all high-pressure microfluidic devices. It is found that the effect of diamondNPs on the PCR performance depends on the nanoparticle concentration; diamaondNPs can improve the PCR performance more than 5 times. On the other hand, if a high concentration of diamondNPs is used, PCR performance decreases significantly. Moreover, it is shown that the fabricated device is able to do the same PCR procedure faster than the commercial PCR devices. Image 1 • A high-throughput two-phase fast PCR device is designed and fabricated. • A new fabrication procedure for high-pressure microfluidic devices is reported. • The effects of Diamond nanoparticles are investigated for enhancing the performance of the PCR device. • It is found that DiamondNP can increase PCR performance ∼5 times depending on its concentration. • The fabricated device can reduce the PCR time more than 40% compared to available PCR methods. [ABSTRACT FROM AUTHOR]

Abstract Whooping cough also called Pertussis is a highly contagious respiratory infection that affects all age populations. Given recent pertussis outbreaks, there is an urgent need for a point-of-care (POC) device for rapid diagnosis of pertussis. Herein, we report a low-cost microfluidic POC device integrated with loop-mediated isothermal amplification (LAMP) technique for the rapid and accurate diagnosis of pertussis. The 3D-printed bioanalyzer housed not only the biochip but also an in-house-developed portable and fully battery-powered heater for rapid POC detection of pertussis, without the need of external electricity. The fluorescence-based results could be rapidly visualized in about one hour by the naked eye without the need for any additional instrumentation. In addition, a simple centrifuge-free sample preparation process was optimized for the efficient lysis of pertussis samples and successfully used for direct detection of bacteria in nasopharyngeal samples. High sensitivity, with a limit of detection (LOD) of 5 DNA copies per LAMP zone, and high specificity were demonstrated. We envision that the microfluidic POC device can be used in various venues such as medical clinics, schools, and other low-resource settings for the fast detection of pertussis. Graphical abstract We report a low-cost microfluidic point-of-care (POC) platform integrated with loop-mediated isothermal amplification (LAMP) supported by a portable battery-powered heater for rapid and instrument-free detection of whooping cough in resource-limited settings. Image 1 Highlights • We for the first time report a low-cost hybrid microfluidic platform integrated with LAMP for rapid and instrument-free detection of whooping cough (pertussis). • We developed a portable and fully battery-powered heater to support on-chip LAMP reactions, which significantly enhanced the capacity for point-of-care detection without the requirement of the external AC power supply. • The microfluidic approach demonstrated high specificity by detecting B. pertussis and other Bordetella species. The limit of detection of 5 DNA copies per LAMP zone was achieved, demonstrating high detection sensitivity. • By using an optimized centrifuge-free lysis protocol, direct detection of B. pertussis bacteria was achieved. • Our novel microfluidic approach has great potential for point-of-care detection of many other pathogens such as foodborne pathogens, especially for low-resource settings. [ABSTRACT FROM AUTHOR]

Abstract In most cases, three-dimensional paper-based microfluidic analytical devices (3D-μPADs) were fabricated manually by stacking or folding methods. For the first time, digital light processing stereolithography (DLP-SLA) 3D printing technology was adopted to automatically make 3D-μPADs. In the fabrication process, a printing pause was set between two layers to allow paper to be placed in the resin tank. The resin on the fresh paper spontaneously bonded to the former cured paper layer during curing, thus realizing the automatic bonding and alignment between different layers of paper and avoiding the human participation and errors as in stacking and folding methods. There was a gap between two vertical aligned flow paths, therefore the liquid did not flow spontaneously from the upper layer to the lower layer. Most of the fluid flow in 3D-μPADs was spontaneous or manually activated, which was not conducive to complex assays that require different regents to be delivered sequentially. Herein, we used an electric field or airflow to trigger the fluid flow and demonstrated the flow controllability by a proof-of-concept colorimetric assay. The limits of detection of glucose and albumin were 0.8 mM and 3.5 μM, respectively, which were sufficient for clinical requirements. Given the characteristic of flow controllability, we believe that the proposed 3D-μPADs have great potential to make paper-based complex assays automated and programmable. Graphical abstract Image 1 Highlights • DLP-SLA 3D printing technology was used to fabricate 3D-μPADs. • Automatic bonding and alignment between different layers of paper were achieved. • The liquid flow in 3D-μPADs was triggered by an electric field or airflow. • Through an electric field or airflow control, detection could be controllable. [ABSTRACT FROM AUTHOR]

Abstract Chloride (Cl−) is an inorganic anion present in a broad range of samples (e.g. biological, environmental, food, water, etc.), the determination of which is of widespread significance. In this work, we translate the well-established traditional argentometric method (Mohr's precipitation titration) into a small, simple, portable, and low-cost paper-based microfluidic diagnostic device, which provides rapid and quantitative analysis. The developed device enables the determination of chloride sample volumes as small as 5 μL. A distance-based detection method is implemented providing fully instrument-free quantitation. The beneficial effects of channel geometry (variable widths with constant heights) on analytical parameters were investigated. Trapezoidal channels (channel width changes linearly with height) were used to create a gradient of paper surface (titrant) available for the reaction, compared to the typical uniform rectangular channels (constant channel width). The trapezoid with increasing width offered higher sensitivity and lower detection limits (i.e. 0.05 mM vs 0.1 mM from the rectangular channel) for chloride determination across the concentration range of 0.05–25 mM. In addition, the effect of concentration of the deposited reagent on the obtained distance signals was investigated using varying concentrations of titrant (AgNO 3), which allowed determination of chloride across a wider dynamic range (up to 200 mM). The utility of the paper devices was demonstrated by determination of chloride in a variety of matrices including body fluids (sweat, serum, and urine) and water samples (drinking, mineral, river water). Graphical abstract Image 1 Highlights • Distance-based μPADs are developed for determination of microscale volume of chloride samples. • Mass transport along asymmetric microfluidic channels is investigated. • Trapezoidal channels are shown to improve the sensitivity of distance-based detection. • Effect of the amount of deposited reagent on distance-signal is investigated. • Performance of the μPADs is demonstrated by testing body fluid and environmental samples. [ABSTRACT FROM AUTHOR]

Abstract In this study, a novel automatic analytical methodology using a titanium dioxide (TiO 2)-assisted preconcentration/ on-site vapor-generation (VG) chip hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) for online determination of mercuric ions (Hg2+) was developed. Interestingly, the TiO 2 nanoparticle (nano-TiO 2) coating on the channel surface acted not only as a sorbent for preconcentration but also as a catalyst for photocatalyst-assisted VG. Under optimum operation conditions, the developed method was validated by analyzing the certified reference material (CRM) Seronorm™ Trace Elements Urine L-2 (freeze-dried human urine). Based on the obtained results, the dramatic reduction of "hands-on" manipulation and the elimination of hazardous materials (e.g., sodium borohydride (NaBH 4) and stannous chloride (SnCl 2)) from the process enabled a simple and ultraclean procedure with an extremely low detection limit of 0.75 ng L−1 for Hg2+ in urine samples. To the best of our knowledge, this is the first study to report the direct exploitation of a nano-TiO 2 -coated microfluidic device for online sample preconcentration and on-site VG prior to ICP-MS measurement. Graphical abstract Image 1 Highlights • An online preconcentration and on-site vapor generation (VG) device was developed. • Nano-TiO 2 acted not only as a preconcentration sorbent but also as a VG catalyst. • Detection limit of 0.75 ng L−1 for Hg2+ was achieved. • This method was successfully applied to determine urinary Hg at ultratrace levels. [ABSTRACT FROM AUTHOR]