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The COVID-19 pandemic exposed difficulties in scaling current quantitative PCR (qPCR)-based diagnostic methodologies for large-scale infectious disease testing. Bottlenecks include lengthy multi-step processes for nucleic acid extraction followed by qPCR readouts, which require costly instrumentation and infrastructure, as well as reagent and plastic consumable shortages stemming from supply chain constraints. Here we report an Oil Immersed Lossless Total Analysis System (OIL-TAS), which integrates RNA extraction and detection onto a single device that is simple, rapid, cost effective, and requires minimal supplies and infrastructure to perform. We validated the performance of OIL-TAS using contrived SARS-CoV-2 viral particle samples and clinical nasopharyngeal swab samples. OIL-TAS showed a 93% positive predictive agreement (n = 57) and 100% negative predictive agreement (n = 10) with clinical SARS-CoV-2 qPCR assays in testing clinical samples, highlighting its potential to be a faster, cheaper, and easier-to-deploy alternative for infectious disease testing., Bottlenecks in qPCR-based COVID-19 diagnostics include the lengthy multistep process and reagent shortages. Here the authors report OIL-TAS which integrates RNA extraction and detection into a single device.

Electrochemical techniques are commonly applied to micro total analysis system (μTAS) devices mainly due to its high sensitivity and miniaturization capacity. Among many electrochemical techniques, capacitively coupled contactless conductivity detection (C4 D) stands out for not requiring direct electrode-solution contact, avoiding several problems such as electrolysis, bubble formation, and metal degradation. Furthermore, the instrumentation required for C4 D measurements is compact, low cost, and easy to use, allowing in situ measurements to be performed even by nonspecialized personal. Contrarily, the production of metallic electrodes and microchannels adequate for C4 D measurements commonly requires specialized facilities and workers, increasing the costs of applying these methods. We propose alternatives to batch manufacture metallic electrodes and polymeric microchannels for C4 D analysis using more straightforward equipment and lower-cost materials. Three devices with different dielectric layer compositions and electrode sizes were tested and compared regarding their analytical performance. The constructed platforms have shown a reduction of more than 64% in cost when compared to traditional techniques and displayed good linearity (R2 ≥ 0.994), reproducibility (RSD ≤ 4.07%, n = 3), and limits of detection (≤0.26 mmol/L) when measuring standard NaCl samples. Therefore, the proposed methods were successfully validated and are available for further C4 D applications such as diagnosis of dry-eye syndrome.

Chain reactions are characterized by initiation, propagation and termination, are stochastic at microscopic scales and underlie vital chemical (e.g. combustion engines), nuclear and biotechnological (e.g. polymerase chain reaction) applications.1–5 At macroscopic scales, chain reactions are deterministic and limited to applications for entertainment and art such as falling domino and Rube Goldberg machines. Appositely, microfluidic lab-on-a-chip (also called a micro total analysis system),6,7 which were envisioned pursuant to microelectronic integrated circuits, are generally not integrated on a chip owing to an enduring dependency on cumbersome connections, peripherals, and on computers for automation.8–11 Capillary microfluidics integrate energy supply and flow control onto a single chip by using capillary phenomena, but programmability remains rudimentary with at most a handful (eight) operations possible.12–19 Here we introduce mesoscopic microfluidic chain reactions (MCRs) based on capillary phenomena for reliable programming and automation of complex liquid handling algorithms integrated in a chip. MCRs are encoded into the chip microarchitecture, 3D printed as a monolithic circuit, and deterministically propagated by the free-energy of a paper pump. With MCR, we sequentially triggered the release of 300 aliquots across chained, interconnected chips, and automated a protocol for SARS-CoV-2 antibodies detection in saliva with visual and quantitative results by cell phone imaging. We automated and miniaturized for the first time the labor-intensive thrombogram with serial and parallel operations including timers and iterative cycles of synchronous flow and stop-flow sequences. Thrombograms with normal, hemophilia-like, and anticoagulant-spiked plasma were generated. MCRs are generalizable, and both the density and number of chain reaction units are scalable. MCRs are untethered from and unencumbered by peripherals, encode programs structurally in situ, and form a frugal, versatile, bona fide lab-on-a-chip with wide-ranging applications in liquid handling and point-of-care diagnostics.

A “ubiquitous human health care system” will require a monolithic optical total analysis system (TAS) consisting of waveguides and microfluidic channels based on a transparent resin chip. Together with the rapid development of the fluorescent marking method, fluorescence analysis by TAS of mixed-microparticle specimen attached to different fluorescent substances will be necessary. Towards realization of this, we here propose a novel method for using a part of the fluorescence acquired by irradiating microparticles with AC-modulated laser power as light dedicated to the discrimination of fluorescent substances. Since the light power for discrimination was extremely weak, we extracted effective signal components using a lock-in detection method. Then, by comparison with the signal of the original fluorescence, we could determine whether the fluorescence signal was from the microparticles attached to the fluorescent substance to be discriminated. Using a mixed specimen composed of microparticle-attached fluorescent substances with emission peaks of 520 nm and 600 nm, we found that 10% of the acquired fluorescence could successfully determine the specified fluorescent substance as a discrimination signal. The peak value of the discrimination signal was approximately double the amplitude of the stationary noise in the discrimination signal.

Refractive index (RI) sensing in microfluidics has the advantage of universal detection, capable of sensing all species from simple monoatomic ions to complex proteins without external labels or additional contrast agents. Various forms of interferometry have been developed for RI sensing in microfluidics. In particular, backscatter interferometry (BSI) is easily implemented and well-suited for miniaturization. This is important for future applications in point-of-care or point-of-interest measurements, where the total analysis system needs to be easily deployed. The optical arrangement in BSI is similar to that used in optical pickup heads (OPHs), found in CD and DVD drives. This offers intriguing possibilities for repurposing OPHs for miniaturized RI detection in microfluidics. To explore the feasibility of this approach, commercially available OPHs are modified for RI detection in 75 μm i.d. (363 μm o.d.) fused silica capillaries. BSI interference patterns measured using a modified OPH positioned near the capillary are compared with simulations as a function of wavelength. Once characterized, the modified OPH is used to measure refractive index changes as sucrose solutions are injected through the 75 μm i.d. capillary. Signal level changes were recorded following the introduction of solutions ranging in concentration from 67 μM to 19.3 mM and the resulting calibration plot (67 μM to 4.8 mM) exhibited good linearity (R2 = 0.9993). Finally, a modified OPH was used to detect the electrophoretic separation of Na+ and Li+ using RI detection. While the measurements reported here used modified OPHs that bypassed the built-in photodiode detector, eventually all on-board components could be utilized for a completely self-contained, inexpensive, universal detector for field deployable microfluidic applications.

The inherent trace quantity of primary fatty acid amides found in biological systems presents challenges for analytical analysis and quantitation, requiring a highly sensitive detection system. The use of microfluidics provides a green sample preparation and analysis technique through small-volume fluidic flow through micron-sized channels embedded in a polydimethylsiloxane (PDMS) device. Microfluidics provides the potential of having a micro total analysis system where chromatographic separation, fluorescent tagging reactions, and detection are accomplished with no added sample handling. This study describes the development and the optimization of a microfluidic-laser induced fluorescence (LIF) analysis and detection system that can be used for the detection of ultra-trace levels of fluorescently tagged primary fatty acid amines. A PDMS microfluidic device was designed and fabricated to incorporate droplet-based flow. Droplet microfluidics have enabled on-chip fluorescent tagging reactions to be performed quickly and efficiently, with no additional sample handling. An optimized LIF optical detection system provided fluorescently tagged primary fatty acid amine detection at sub-fmol levels (436 amol). The use of this LIF detection provides unparalleled sensitivity, with detection limits several orders of magnitude lower than currently employed LC-MS techniques, and might be easily adapted for use as a complementary quantification platform for parallel MS-based omics studies.

Point-of-care diagnostic devices aid in the early and rapid detection of immunological markers leading to better medical outcomes. Lateral flow immunoassays (LFIA) are fast assays that provide both qualitative and semi-quantitative results on site. Sample preparation for LFIA tests is usually done manually with multiple mixing steps and is prone to errors. The iQuant Auto is an entirely automated system that can handle sample preparation, effective transfer to lateral flow test membrane, and subsequent result estimation. The system uses a pneumatic system for fluid handling and sample preparation, and an image-based fluorescence reader for reaction visualization. The device works with test specific milli-fluidic lateral flow kit called iQPrep Kit, which has integrated reagent storage areas and valves for fluid control. The test kit can be manufactured using standard manufacturing techniques and can be produced at scale cheaply. The iQPrep Kit can be modified to test for various markers like HbA1c, Vitamin D, and TSH, while the hardware for sample preparation and the fluorescence reader remains the same. The device has a minimalist and intelligible graphical interface aiding smooth operation by less skilled people at resource-limited settings. Standard reference cartridges of different volume ratios were used to validate the functionality of the instrument. The intra- instrument coefficient of variation (CoV) of the mobile kit reader was found to be less than 0.62%. The positional accuracy of the system to ensure precise kit engagement with the other auxiliary systems was checked, and the CoV was 0.16%. The fluid handling capabilities were tested, and it was found that an average fluid loss of 10 µl results due to the liquid adherence to fluid channel walls and valve interfaces. The iQuant Auto is an easily operable, total analysis system for immunodiagnostics.

The coronavirus disease 2019 (COVID-19) pandemic exposed difficulties in scaling current quantitative PCR (qPCR)-based diagnostic methodologies for large-scale infectious disease testing. Bottlenecks include the lengthy multi-step process of nucleic acid extraction followed by qPCR readouts, which require costly instrumentation and infrastructure, as well as reagent and plastic consumable shortages stemming from supply chain constraints. Here we report a novel Oil Immersed Lossless Total Analysis System (OIL-TAS), which integrates RNA extraction and detection onto a single device that is simple, rapid, cost effective, uses minimal supplies and requires reduced infrastructure to perform. We validated the performance of OIL-TAS using contrived samples containing inactivated SARS-CoV-2 viral particles, which show that the assay can reliably detect an input concentration of 10 copies/μL and sporadically detect down to 1 copy/μL. The OIL-TAS method can serve as a faster, cheaper, and easier-to-deploy alternative to current qPCR-based methods for infectious disease testing.

The authentication of animal species is an important issue due to an increasing trend of adulteration and mislabeling of animal species in processed meat products. Polymerase chain reaction is the most sensitive and specific technique for nucleic acid-based animal species detection. However, it is a time-consuming technique that requires costly thermocyclers and sophisticated labs. In recent times, there is a need of on-site detection by point-of-care (POC) testing methods and devices under low-resource settings. These POC devices must be affordable, sensitive, specific, user-friendly, rapid and robust, equipment free, and delivered to the end users. POC devices should also confirm the concept of micro total analysis system. This review discusses POC testing methods and devices that have been developed for meat species identification. Recent developments in lateral flow assay-based devices for the identification of animal species in meat products are also reviewed. Advancements in increasing the efficiency of lateral flow detection are also discussed.

Micro total analysis system (μTAS) is expected to be applied in various fields. In particular, since electrochemical measurement is inexpensive and easy, electrochemical measurement can be integrated with a microchannel. However, electrochemical detection sensitivity in a microchannel is lowered because the diffusion of the detection target is limited. In an ordinary electrochemical detection system, using a stirrer in a beaker can overcome limited diffusion. We previously proposed a new detection system that combines a microliquid solution agitation technology using surface acoustic waves (SAWs) with the μTAS. The SAWs function as microstirrers, thus making electrochemical detection possible by overcoming limited diffusion of the sample. However, when the solution is stirred by the SAWs, the temperature of the solution increases to 70°C due to vibrational energy. This leads to enzyme inactivation and impaired electrochemical response. Therefore, in this study, we used a hyperthermophile-derived enzyme. Temperature and electrochemical characteristics of the detection system using SAWs and a multi-copper oxidase (MCO) derived from the hyperthermophilic archaea Pyrobaculum aerophilum were studied. Laccase, which is an MCO derived from the thermophilic fungus Trametes versicolor, was also studied. We also characterized the enzyme-electrochemical reaction using SAWs by comparing the magnitude of the reduction current obtained using the two enzymes with different heat resistances. We observed an increase in the electrochemical response with the SAWs, without impaired enzyme activity. Thus, the use of a thermostable enzyme is suitable for the development of a biosensor that uses SAWs for agitation.

We report the development of a micro total analysis system (μTAS) based on electrochemical measurements and dielectrophoretic sorting for screening of NAD(P)-dependent oxidoreductases. In this system, the activity of enzymes immobilized on microbeads, together with their encoding DNA, can be measured with a boron-doped diamond (BDD) electrode in each compartment (∼30 nL) of the microfluidic system. The 30 nL droplets containing microbead-displayed genes of enzymes with higher activity can then be recovered by dielectrophoretic sorting. Previously, we developed the NAD(P)H-measuring device containing the BDD electrode for high-throughput measurement of the activity of NAD(P)-dependent oxidoreductases. In this study, we fabricated an encapsulating device and a droplet-sorting device for nanoliter-size droplets, for the first time, and then combined these three devices to construct a μTAS for directed evolution of NAD(P)-dependent oxidoreductases. We confirmed that this system works by proof-of-principle experiments and successfully applied this system for screening of randomized libraries of NAD-dependent dehydrogenases.

A miniaturised total analysis system (μTAS) was originally defined as “a system that periodically performs ALL sample handing steps required to translate chemical into electronic information at a location that is extremely close to the point of sample collection”(Manz, Sens Actuators B-Chem, 1990). Following rapid progress developing functional units, the integration of these units to allow the automated execution of the analytical workflow has proven to be challenging, especially when taking out-scaling of manufacturing into account. Over almost three decades, scientists and engineers have worked together and microfluidic units have become part of a wide range of instruments. Growing demands from diagnostics sector for point of collection analysis have driven the development of functionally integrated microfluidic devices with sample in/answer out capability. The focus of this review is on the systems that go one step further and are capable of periodically executing the analytical protocol to translate the chemical information into electronic data. With sampling and chip to world interfacing fundamental to a μTAS’ operation, an overview of flow-based sampling techniques is provided, followed by selected examples of μTASs applied for monitoring environmental, biochemical, and physiological processes and extra-terrestrial exploration. Building on the expertise developed in the development of Lab on a Chip systems and innovations in manufacturing, automation and control, the future outlook for μTASs to stream the chemical data required to advance our understanding and subsequently control of the processes in- and around us is looking bright.

Droplet based microfluidics (DBMF) has gained huge recognition in the recent years for performing micro-reactions in droplets with high throughput, sensitivity, specificity and minimum cross-contaminations. This technology enables the researchers to realize highly reliable and rapid detection and screening applications in various fields. The high-throughput nature of droplet microfluidics generates large amounts of valuable but complex droplet dataset. Deeper analysis of this intricate droplet data is very essential for detection, classification, characterization and quantification of reactions/content inside the droplets. This can be carried out by Machine Learning (ML), which has proven itself in processing and providing deeper insights and precise predictions of relatively large amounts of complex data with shorter analysis times and exceptional accuracy. The analytical tools of ML enable to imbibe automation and control of many such diagnostic platforms, including DBMF, with minimum human intervention. In recent times, the potential of ML has been explored in microfluidic technology as well to tackle challenges in biomedical and biotechnological applications. The synergy of both the fields, DBMF and ML, helps in development of optimized and automated tools with higher accuracy for numerous applications. Specifically, this enables complete comprehension of the field to eventually realize a truly microfluidic total analysis system (µTAS). This work comprehends a general review emphasizing the implementation of different ML models with DBMF to automate various activities such as fluid control, droplet size prediction, recognition of flow pattern and identification, classification and sorting of droplets in a microfluidic device.

In-line preconcentration techniques are used to improve the sensitivity of microfluidic DNA analysis platforms. The most common methods are electrokinetic and require an externally applied electric field. Here we describe a microfluidic DNA preconcentration technique that does not require an external field. Instead, pressure-driven flow from a fluid-filled microcapillary into a lower ionic strength DNA sample reservoir induces spontaneous DNA migration against the direction of flow. This migratory phenomenon that we call Molecular Rheotaxis initiates in seconds and results in a concentrated DNA bolus at the capillary orifice. We demonstrate the ease with which this concentration method can be integrated into a microfluidic total analysis system composed of in-line DNA preconcentration, size separation, and single-molecule detection. Paired experimental and numerical simulation results are used to delineate the parameters required to induce Molecular Rheotaxis, elucidate the underlying mechanism, and optimize conditions to achieve DNA concentration factors exceeding 10,000 fold., Implementing a nucleic acid preconcentration method can improve the sensitivity of microfluidic analysis systems. Here Friedrich et al. concentrate DNA by many orders of magnitude using pressure-driven flow, which could lead to a simple and practical microanalysis platform.

The isolation of nucleic acids in the lab on a chip is crucial to achieve the maximal effectiveness of point-of-care testing for detection in clinical applications. Here, we report on the use of a simple and versatile single-channel microfluidic platform that combines dimethyl pimelimidate (DMP) for nucleic acids (both RNA and DNA) extraction without electricity using a thin-film system. The system is based on the adaption of DMP into nonchaotropic-based nucleic acids and the capture of reagents into a low-cost thin-film platform for use as a microfluidic total analysis system, which can be utilized for sample processing in clinical diagnostics. Moreover, we assessed the use of the DMP system for the extraction of nucleic acids from various samples, including mammalian cells, bacterial cells, and viruses from human disease, and we also confirmed that the quality and quantity of the nucleic acids extracted were sufficient to allow for the robust detection of biomarkers and/or pathogens in downstream analysis. Furthermore, this DMP system does not require any instruments and electricity, and has improved time efficiency, portability, and affordability. Thus, we believe that the DMP system may change the paradigm of sample processing in clinical diagnostics.

This paper presents a micro total analysis system (microTAS) integrating digital microfluidics, acoustic wave microsensors and electronic circuits for rapid sample screening based on liquid bulk modulus measurement. The microsystem is designed for in-field analysis where a number of liquid samples need to be processed in a short time. As a preliminary validation, the microsystem processed 7 glycerol-water mixture samples in less than 3 minutes (from sample loading and delivery to measurement and waste collection). In another experiment, the microsystem processed 6 samples in parallel in just 5 seconds. The experimental results demonstrate the features of fast samples-to-results, low consumption, reliable screening ability and high-throughput potentials.

Proactive water pathogen identification process holds significance in view of increasing bioterrorism prospects, quantification of virulence properties and water supply regulation for human welfare. Strikingly, pathogen concentration is rather low in water bodies to be identified using conventional methods and usually involves three typical steps: 1) concentration 2) purification and 3) characterization and assay. Surface enhanced Raman scattering (SERS) analysis on other hand could easily surpass these steps to give a rather robust identification owing to its exceptionally high specificity and sensing abilities. In this article we use SERS as a diagnostic tool to identify low concentrations of noxious pathogens from water, using a two level confinement that results in a superlative SERS analytical assay, capable of analyte identification down to single molecule level. Unlike the regular dip coat process, we restrict the nanostructure deposition only to a very small area of the larger substrate, by restricting its application volume. In this way, we limit our data processing time, increase our probability of target interaction and also reduce nanostructure/analyte sample quantities for analysis. To enhance the signal intensities further, we use natural three phase pinning or the coffee ring effect to pre-concentrate the analytes on our spatially confined nanostructure pocket, allowing maximal deposition at the edges and subsequently higher signal intensities. The methodology was employed to measure the presence of S. aureus and R6 G in spiked drinking water. LOD achieved for R6 G and S. aureus is 10−12 M and 103 CFU/ml respectively. The increasing signal intensities share a linear relationship with analyte concentration. The acquired signals were reproducible and non-degenerate, overcoming the drawback of irregular data patterns associated with conventional metal nanostructure based SERS systems. Estimated RSD value for physical confinement and coffee ring effect measured was 11.6% and 8.37% respectively. This simple, low cost, robust and reproducible method can be useful for increasing the sensitivity of SERS based detection devices with capability to be developed into a micro total analysis system (μTAS).

Recently, the microfluidic system is one of the most trending research topics in the world due to its unique characteristics and great advantages...

Nanomaterials have several advantages in detecting several biomaterials and in enhancing signals and their inherent effects. Thus, they have been widely applied in the biomedical fields such as biosensor and cancer therapeutics. Recently, the development of microfluidic technology has led to superior biological analysis systems to detect biomarkers related to diseases or serve as in vitro drug screening platform. In a microfluidic device, samples could be analyzed more accurately, rapidly and simply. In addition, it is possible to culture the cells in these microfluidic devices, therefore making the in situ analysis of secretomes easy. Nanomaterials can be easily applied in the microfluidic channels as capturing and signaling materials in order to improve the sensing or therapeutic property. In particular, nanomaterial integrated microfluidic cell culture model can replace in vivo disease models for nanotherapeutics screening. In this review, nanomaterial-based sensing systems, which include diverse organic and inorganic nanoparticles, are introduced with specific examples, including microfluidics integrated systems. Moreover, microfluidics derived nanomaterial analytic systems as in vitro 2 or 3-dimensional (2D or 3D) cell culture platform will be presented. We also highlight the future perspectives of the microfluidic-driven system as highly sensitive total analysis system with functional nanoparticles.

An optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the functional components that will be needed to realize a “ubiquitous human healthcare system” in the near future. We have already proposed the fundamental structure for a light waveguide capable of irradiating a living cell or particle running along a microfluidic channel, and of detecting fluorescence even from the extremely weak power of a minute particulate body. In order to foster advanced functions for obtaining information concerning the internal structure of living cells or particles conveniently, an angular scanning method that sequentially changes the direction in which the minute cell or particle is irradiated may be crucial. In this paper, we investigate fluorescence detection from resin particles attached to a fluorescent substance by switching irradiation direction of the exciting laser source power using a newly fabricated TAS chip with a unique intersection structure. To construct the experimental system cost effectively, we adopted a special light waveguide structure in which the intersection to a fluidic channel was arranged radially, with laser power inlet/outlet portions arranged in parallel. In addition, we incorporated a forced vibration mechanism on an optical fiber apex to construct a simple light-switching system. Preliminary experiments combining this unique TAS chip and the optical scanning mechanism revealed that the function of the radially arranged light waveguide switching worked adequately, and variation of transmittance of each light waveguide was accurately evaluated. Results were successfully applied to compensation of detected angular scanning signals. Finally, we performed an angular scanning experiment for a fluorescent substance attached to a microparticle under conditions of higher intersection-passing velocity of several 10s mm/s (single-shot scanning) and lower intersection-passing velocity of several mm/s (multiple-shot scanning). Based on the obtained scanning data, we successfully constructed directivities of emitting fluorescence from particles, and clarified that fluorescence emission indicated its peak at the forward and orthogonal directions of the incident light beam.

Liquid and gas flow sensors are important components of the micro total analysis systems (μTAS) for modern analytical sciences. In this paper, we proposed a self-powered triboelectric microfluidic sensor (TMS) by utilizing the signals produced from the droplet/bubble via the capillary and the triboelectrification effects on the liquid/solid interface for real-time liquid and gas flow detection. By alternating capillary with different diameters, the sensor's detecting range and sensitivity can be adjusted. Both the relationship between the droplet/bubble and capillary size, and the output signal of the sensor are systematically studied. By demonstrating the monitoring of the transfusion process for a patient and the gas flow produced from an injector, it shows that TMS has a great potential in building a self-powered micro total analysis system.

Micro total analysis system or Lab-on-a-chip, in which microfluidic chips are significant components, has caused wide attention in recent years. CD/DVD manufacturing technology is a highly efficient and low-cost solution to fabricate microfluidic chips. In this paper, microfluidic chips made of polycarbonate (PC) were firstly fabricated by CD/DVD manufacturing technology. The manufacturing process is divided to five main sub-processes which are photomask fabrication, photolithography, electroforming, stamping and thermal bonding. Besides, by repeatedly bonding for three times, the bonding success percentage of the chip could reach about 98 %. The surface roughness of the microstructure in microfluidic chips which has significant influences on thermal bonding success percentage and test results are also detailedly studied. Surface roughness of SU-8 pattern, Ni stamper and cover slips of PC microfluidic chips was measured and analyzed. In the process of electroforming and stamping, the surface roughness is increased. Moreover, influences of cover slips' surface roughness on thermal bonding are analyzed by bonding five groups of cover slips on PC plates with different average surface roughness. The thermal bonding success percentage is obviously reduced with the increase of average surface roughness.

The progress made in recent years in the area of micro total analysis system (μ-TAS) has allowed the development of analytical tools for determination and measurement of elements and compounds that previously required bench laboratory equipment for such purposes. μ-TAS provides a high degree of sensitivity and they are simple and affordable. This work details a process by which classical colorimetric methodologies used in analysis have been adapted from discontinuous to continuous flow systems, for determination of cobalt in aqueous solutions in real time. The purpose of this adaptation is the subsequent system miniaturization using low temperature co-fired ceramics (LTCC). The adapted methodology for the colorimetric determination of cobalt uses 3-Hydroxy-4-nitroso-2,7-naphtalene disulfonic acid disodium salt or nitroso-R salt (NRS) as the main reagent, in an environment of acetate and sodium citrate which favors the reaction. The carrier solution is prepared with sulfuric acid. The system encompasses a microfluidic structure in LTCC, a peristaltic pump to maintain the continuous flow, a six-way valve for sample injection, and an issuer of light of 540 nm based on a multiled. Using the integrated circuit TCS3414, the signal is sent to the computer wirelessly through zigbee protocol, and at the end a LabVIEW-based application shows the absorbance for a range of concentrations between 0.5 and 10 mg/L.

It has long been thought that an optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the functional components that will be needed to realize a "ubiquitous human healthcare system" in the near future. We have already proposed the fundamental structure for a light waveguide capable of illuminating a living cell or particle running along a microfluidic channel, as well as of detecting fluorescence even from the extremely weak power of such a minute particle. In order to develop novel functions to detect the internal structure of living cells quickly, an angular scanning method that sequentially changes the direction of illumination of the minute cell or particle may be crucial. In this paper, we investigate fluorescence detection from moving particles by switching the laser power delivery path of plural light waveguides as a preliminary experiment toward this novel method. To construct an experimental system able to incorporate a switching light source mechanism cost effectively, we utilized a conventional TAS chip with plural waveguide pairs arranged in parallel, and a forced vibration mechanism on an optical fiber tip by a piezoelectric actuator. With this system, we performed an experiment to detect extremely weak fluorescence using micro particles with a fluorescent substance attached and an optical TAS chip that incorporated a microfluidic channel and three pairs of laser-power-delivering light waveguide cores. We successfully obtained clear, quasi-triangular-shaped pulses in fluorescent signals from resin particles running across the intersection under three different conditions: (1) a particle with approximately the same velocity as that of a forced-vibrated optical fiber tip of approximately 700 mm/s, (2) a particle with velocity 1 digit smaller than that of an optical fiber tip, and (3) a particle with velocity approximately 1/20 that of an optical fiber tip.

The global risk of viral disease outbreaks emphasizes the need for rapid, accurate, and sensitive detection techniques to speed up diagnostics allowing early intervention. An emerging field of microfluidics also known as the lab-on-a-chip (LOC) or micro total analysis system includes a wide range of diagnostic devices. This review briefly covers both conventional and microfluidics-based techniques for rapid viral detection. We first describe conventional detection methods such as cell culturing, immunofluorescence or enzyme-linked immunosorbent assay (ELISA), or reverse transcription polymerase chain reaction (RT-PCR). These methods often have limited speed, sensitivity, or specificity and are performed with typically bulky equipment. Here, we discuss some of the LOC technologies that can overcome these demerits, highlighting the latest advances in LOC devices for viral disease diagnosis. We also discuss the fabrication of LOC systems to produce devices for performing either individual steps or virus detection in samples with the sample to answer method. The complete system consists of sample preparation, and ELISA and RT-PCR for viral-antibody and nucleic acid detection, respectively. Finally, we formulate our opinions on these areas for the future development of LOC systems for viral diagnostics., Graphical abstract Image 1, Highlights • Conventional methods for viral detection are time consuming and labor intensive. • Newly emerged microfluidic devices can perform practically any conventional laboratory technique. • Here we concentrated on microfluidics-based viral detection by immunoassays as well as by nucleic acid amplification. • We used a few examples of successfully commercialized rapid devices. • We discuss perspectives for technology of viral detection in near future.

The micropump is the most important functional unit of a micro total analysis system (μTAS). An ideal microfluidics system should adopt simple, stable, robust, inexpensive, and integrated on-chip strategies to transport samples for downstream applications, with little or no external energy consumption and limited manual intervention. Nevertheless, it remains a key challenge for traditional micropumps to be directly integrated into self-contained and disposable μTAS for velocity-stable and passive sample transport. The best way to assess the capability of passive micropumps is to evaluate their pumping performance in extreme environments, e.g. a 3D configurated microchannel instead of a 2D configuration, high temperature conditions instead of at room temperature, a long microchannel instead of short microchannel, a complex topological microsystem (e.g. a microvascular network interconnecting multiple inlets and outlets) instead of a simple topological microsystem (e.g. a one-directional microchannel connecting only one inlet and one outlet), and multi-phase microdroplet transport instead of single-phase plug transport. In this review, a novel micropumping methodology - a pressure-driven gas-diffusion/permeation micropump - is described, which is the first review paper dedicated to this subject. A comprehensive overview is provided for comparison between this novel micropumping methodology and traditional passive micropumps, especially for applications in stable velocity control in the aforementioned extreme environments. Compared with mainstream conventional micropumps, we confirm that pressure-driven gas-diffusion/permeation micropumps combine a number of superior properties all into one device, such as small size, simple structure, without the need for microfabrication procedures or external power consumption, strong transport capacity, homogeneous flow velocity, delivery capacity for both multi-phase microdroplets and single-phase plugs, long-distance transport, persistent pumping for both 3D microchannels and complex topological microsystems (e.g. a biomimetic microvasculature), low cost, ease of microdevice integration, bubble suppression and amazing stability at high temperatures. An advanced outlook and perspectives for the future development of this novel micropump are also discussed, which may serve as a starting point for researchers in the microfluidics fields to harness pressure-driven gas-diffusion/permeation micropumps for downstream applications.

Micro total analysis system (μTAS) or lab-on-a-chip (LOC) technology has advanced over decades, and the high performance for chemical and biological analysis has been well demonstrated with advantages of low sample consumption, rapid analysis time, high-throughput screening, and portability. In particular, μTAS or LOC based genetic applications have been extensively explored, and the short tandem repeat (STR) typing on a chip has garnered attention in the forensic community due to its special use for human identification in the field of mass disaster and missing person investigation, paternity testing, and perpetrator identification. The STR typing process consists of sample collection, DNA extraction, DNA quantitation, STR loci amplification, capillary electrophoretic separation, and STR profiling. Recent progress of microtechnology shows its ability to substitute the conventional analytical tools, and furthermore demonstrates total integration of the whole STR processes on a single wafer for on-site STR typing. In this review article, we highlighted some representative results for fluorescence labeling techniques, microchip-based DNA purification, on-chip polymerase chain reaction (PCR), a capillary electrophoretic microdevice, and a fully integrated microdevice for STR typing.

It has long been thought that an optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the essential functional components needed to realize a "ubiquitous human healthcare system". In accordance with this, we have proposed the fundamental structure for a light waveguide capable of illuminating a cell or particle running along a microfluidic channel and detecting fluorescence even from the extremely weak power of such a minute particle. We successfully trial-manufactured an optical TAS chip with a microfluidic channel containing a 15 × 20-μm cross-section, and a higher aspect ratio (6-μm wide, 10-μm high) core of a light waveguide. To obtain extremely weak forward- and side-direction emitted fluorescence within the chip, we utilized the L- or T-shaped microfluidic channels used in previous studies. As we could predict the fluorescent substances would have very low efficiency, we created a high-power light source using a semiconductor laser (488-nm-wavelength), and a high-performance fluorescence detecting optical system, consisting mainly of a dichroic mirror and interference filters. With this system, we were able to obtain fluorescent responses emitted from substances attached to a particle, adjusting gains in value of the maximum photoelectron multiplier tube modules. Response signal waveforms indicated higher signal-to-noise ratio in forward-direction emitted fluorescence and side-direction emitted. These two detected fluorescences and the side-scattered source light were fully synchronized. Furthermore, a series of experiments revealed that the forward-direction and side-direction emitted fluorescence components had approximately the same order of magnitude. Typical pulse magnitude detected in both directions ranged from 1 pW to several hundreds of pW.

Blood is the gold standard sample medium that can provide a wide variety of useful biological information for the diagnosis of various diseases. For portable point-of-care diagnosis, blood extraction systems have attracted attention as easier, safer, and more rapid methods of collecting small blood volumes. In this paper, we introduce a novel self-powered one-touch blood extraction system created by assembling a smart polymer-capped hollow microneedle in a pre-vacuum polydimethylsiloxane actuator. The optimized hollow microneedle was precisely fabricated by drawing lithography for minimally invasive blood extraction, with a length of 1800 μm, an inner diameter of 60 μm, an outer diameter of 130 μm, and a bevel angle of 15°. The system utilizes only a single step for operation; a finger press activates the blood sampling process based on the negative pressure-driven force built into the pre-vacuum activated actuator. A sufficient volume of blood (31.3 ± 2.0 μl) was successfully extracted from a rabbit for evaluation using a micro total analysis system. The entire system was made of low-cost and disposable materials to achieve easy operation with a miniature structure and to meet the challenging requirements for single-use application in a point-of-care system without the use of any external power equipment.