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A novel assay platform consisting of a finger pump microchip (FPM) and a WiFi-based analytical detection platform is presented for measuring the concentration of methylparaben (MP) in commercial foods. In the presented approach, a low quantity (5 μL) of distilled food sample is dripped onto the FPM and undergoes a modified Fenton reaction at a temperature of 40 °C to form a green-colored complex. The MP concentration is then determined by measuring the color intensity (RGB) of the reaction complex using APP software (self-written) installed on a smartphone. The color intensity Red(R) + Green(G) value of the reaction complex is found to be linearly related (R

A novel assay platform consisting of a microfluidic sliding double-track paper-based chip and a hand-held Raspberry Pi detection system is proposed for determining the albumin-to-creatine ratio (ACR) in human urine. It is a clinically important parameter and can be used for the early detection of related diseases, such as renal insufficiency. In the proposed method, the sliding layer of the microchip is applied and the sample diffuses through two parallel filtration channels to the reaction/detection areas of the microchip to complete the detection reaction, which is a simple method well suited for self-diagnosis of ACR index in human urine. The RGB (red, green, and blue) value intensity signals of the reaction complexes in these two reaction zones are analyzed by a Raspberry Pi computer to derive the ACR value (ALB and CRE concentrations). It is shown that the G + B value intensity signal is linearly related to the ALB and CRE concentrations with the correlation coefficients of R2 = 0.9919 and R2 = 0.9923, respectively. It is additionally shown that the ALB and CRE concentration results determined using the proposed method for 23 urine samples were collected from real suffering chronic kidney disease (CKD) patients are in fine agreement with those acquired operating a traditional high-reliability macroscale method. Overall, for point-of-care (POC) CKD diagnosis and monitoring in clinical applications, the results prove that the proposed method offers a convenient, real time, reliable, and low-spending solution for POC CKD diagnosis.

An electrochemical-biosensor (EC-biosensor) microchip consisting of screen-printed electrodes and a double-layer reagent paper detection zone impregnated with amaranth is proposed for the rapid determination of microalbuminuria (MAU) in human urine samples. Under the action of an applied deposition potential, the amaranth is adsorbed on the electrode surface and the subsequent reaction between the modified surface and the MAU content in the urine sample prompts the formation of an inert layer on the electrode surface. The inert layer impedes the transfer of electrons and hence produces a drop in the response peak current, from which the MAU concentration can then be determined. The measurement results obtained for seven artificial urine samples with known MAU concentrations in the range of 0.1–40 mg/dL show that the measured response peak current is related to the MAU concentration with a determination coefficient of R2 = 0.991 in the low concentration range of 0.1–10 mg/dL and R2 = 0.996 in the high concentration range of 10–40 mg/dL. Furthermore, the detection results obtained for 82 actual chronic kidney disease (CKD) patients show an excellent agreement (R2 = 0.988) with the hospital analysis results. Overall, the results confirm that the proposed detection platform provides a convenient and reliable approach for performing sensitive point-of-care testing (POCT) of the MAU content in human urine samples.

Lab-on-paper, or microfluidic paper-based analytical devices (μPADs), use paper as a substrate material, and are patterned with a system of microchannels, reaction zones and sensing elements to perform analysis and detection. The sample transfer in such devices is performed by capillary action. As a result, external driving forces are not required, and hence the size and cost of the device are significantly reduced. Lab-on-paper devices have thus attracted significant attention for point-of-care medical diagnostic purposes in recent years, particularly in less-developed regions of the world lacking medical resources and infrastructures. This review discusses the major advances in lab-on-paper technology for blood analysis and diagnosis in the past five years. The review focuses particularly on the many clinical applications of lab-on-paper devices, including diabetes diagnosis, acute myocardial infarction (AMI) detection, kidney function diagnosis, liver function diagnosis, cholesterol and triglyceride (TG) analysis, sickle-cell disease (SCD) and phenylketonuria (PKU) analysis, virus analysis, C-reactive protein (CRP) analysis, blood ion analysis, cancer factor analysis, and drug analysis. The review commences by introducing the basic transmission principles, fabrication methods, structural characteristics, detection techniques, and sample pretreatment process of modern lab-on-paper devices. A comprehensive review of the most recent applications of lab-on-paper devices to the diagnosis of common human diseases using blood samples is then presented. The review concludes with a brief summary of the main challenges and opportunities facing the lab-on-paper technology field in the coming years.

Cyclamate is an artificial sweetener with high sweetness and low calories, and is a common sugar substitute for weight control and diabetic patients. However, excessive cyclamate consumption is associated with various health disorders, and hence it is prohibited as a food additive in many countries around the world. The current research proposes a light-shading reaction microfluidic PMMA/paper detection (MPD) system for determining the cyclamate concentration in food. In the current system, inject 10 μL of the extracted sodium cyclamate sample into the sample chamber of the MPD device, perform the diazotization reaction under shading conditions, and then suck it into the detection area through a paper strip, which consists of a paper chip embedded with modified Bratton-Marshall reagent. Once the paper chip is thoroughly wetted, the MPD device is inserted into a microanalysis box, where a fuchsia azo reaction compound is produced through heating at 40 °C for 3 min. The reaction complex is observed by a camera and the reaction image is wirelessly transmitted to a smartphone, and the concentration of sodium cyclamate is measured through the self-developed grayscale software. The results obtained for the sodium cyclamate samples with a concentration in the range of 50-1000 ppm show that the measured gray value changes linearly with the sodium cyclamate concentration, and the correlation coefficient (R

Due to the sparsity in knowledge, we investigated the presence of various estrogenic endocrine-disrupting chemicals (EEDCs), including phthalates (PAEs), bisphenol-A (BPA), and nonylphenol (NP), as well as microplastics (MPs) in samples of the most widely consumed fish collected from different estuaries in northern Taiwan. We then proceeded to determine the likely contribution that this exposure has on the potential for health impacts in humans following consumption of the fish. Six hundred fish caught from five river estuaries (producing 130 pooled samples) were analyzed to determine how different factors (such as the river, benthic, pelagic, and migratory species) influence EEDCs’ contamination and the possible impacts on human health following typical consumption patterns. The predominant EEDCs was diethyl phthalates (DEP), bis (2-ethylhexyl) phthalates (DEHP), and di-iso-nonylphthalate (DINP) in fish, present at 52.9 ± 77.3, 45.3 ± 79.8, and 42.5 ± 79.3 ng/g dry weight (d.w.), respectively. Residual levels of NP, BPA, and MPs in the fish were 17.4 ± 29.1 and 1.50 ± 2.20 ng/g d.w. and 0.185 ± 0.338 mg/g d.w., respectively. EEDCs and MPs levels varied widely among the five river estuaries sampled due, in part, to differences in habitat types and the associated diversity of fish species sampled. For DEP, the Lao-Jie River and pelagic environments produced the most severely contaminated fish species, respectively. DEP residues were also associated with the burden of MPs in the fish. Based on our analysis, we predict no substantial direct human health risk by EEDCs based on typical consumption rates of estuarine fish by the Taiwanese people. However, other sources of EEDC exposure cannot be ignored.

A multifunctional microchip-based distillation apparatus is presented for the distilled of sulfur dioxide (SO2) in food products. The microchip is fabricated on poly(methyl methacrylate) (PMMA) substrates, and comprises a sample zone, a buffer zone, a serpentine distillation column, and a collection zone. In the process, the sample is introduced into the sample zone and is heated under carefully controlled temperature and time conditions. The resulting SO2 and water vapor are carried by nitrogen (N2) gas to the distillation column, where the SO2 is separated from the water vapor via the condensing effects of a continuous cold water flow. Finally, the SO2 is transported to the collection zone, where it is collected with hydrogen peroxide (H2O2) and its concentration determined using an alkali-based titration and paper-based detection method. A distillation efficiency of 90.5% is obtained under the optimal distillation conditions at concentrations of 20–4000 ppm. Moreover, a linear correlation (R2 = 0.9997) is observed between the experimental measurements of the SO2 concentration and the known concentration. The validity of the presented microchip-based distillation apparatus is further investigated by distilling the SO2 concentrations of 25 commodity samples. The detection results show that the deviation does not exceed 5.4% compared with the traditional official method.

Insulator-based dielectrophoresis has to date been almost entirely restricted to Newtonian fluids despite the fact that many of the chemical and biological fluids exhibit non-Newtonian characteristics. We present herein an experimental study of the fluid rheological effects on the electroosmotic flow of four types of polymer solutions, i.e., 2000 ppm xanthan gum (XG), 5% polyvinylpyrrolidone (PVP), 3000 ppm polyethylene oxide (PEO), and 200 ppm polyacrylamide (PAA) solutions, through a constriction microchannel under DC electric fields of up to 400 V/cm. We find using particle streakline imaging that the fluid elasticity does not change significantly the electroosmotic flow pattern of weakly shear-thinning PVP and PEO solutions from that of a Newtonian solution. In contrast, the fluid shear-thinning causes multiple pairs of flow circulations in the weakly elastic XG solution, leading to a central jet with a significantly enhanced speed from before to after the channel constriction. These flow vortices are, however, suppressed in the strongly viscoelastic and shear-thinning PAA solution.

A rapid analytical platform composed of a paper-based chip (µPB-Chip) and a small analytic box is developed to determine the concentration of human serum albumin (HSA). In this study, a Bromocresol Green (BCG) reagent is dropped into the reaction area of the µPB-Chip, and the HSA concentration was derived from the R (red) value intensity of the albumin-BCG complex formed after a reaction process at 37 °C for 12 min. The effectiveness of the developed method is displayed using albumin concentrations ranging from 0 to 5 g/dL in HSA control samples. The measurement results acquired from 36 volunteer patient’s HSA samples are presented to be in good consistency with those obtained utilizing a conventional assay technique (R2 = 0.9912). Ultimately, the results show that the developed platform provides a convenient, economical and dependable method for HSA concentration detection.

A method is proposed for determining the concentration of albumin (ALB) in human whole blood samples using a 3-dimensional (3D) microfluidic paper-based chip and a smart detection module. In fabricating the paper-based chip, the reaction area is implanted with bromocresol green (BCG) reagent and the device is stored in a nitrogen (N2) environment at a temperature of —15 °C until needed for use. In the detection process, 10 μl of whole blood is dropped onto the entrance area of the chip and the plasma within the sample diffuses through a separation channel into the reaction zone. A reaction is induced between the ALB in the plasma and the BCG reagent in the reaction area by heating the chip at 37 °C for 6 min. The ALB concentration is then detected using a colorimetry technique implemented on a cell phone in the form of a self-written app. It is shown that the detection results obtained for 40 pure ALB samples and 30 whole blood samples are consistent with those obtained using a traditional spectrophotometry method (R2 = 0.9837 and R2 = 0.9968). The proposed detection system thus provides a reliable tool for practical ALB determination purposes.

A microfluidic colorimetric detection (MCD) platform consisting of a sliding hybrid PMMA/paper microchip and a smart analysis system is proposed for the convenient, low-cost and rapid analysis of human urine and whole blood samples. The sliding PMMA/paper microchip comprises a PMMA microfluidic chip for sample injection and transportation, a paper strip for sample filtration (urine) or separation (blood), and a sealed paper-chip detection zone for sample reaction and detection. In the proposed device, the paper-chip is coated with bicinchoninic acid (BCA) and biuret reagent and is then assembled into the PMMA microchip and packaged in aluminum housing. In the detection process, the PMMA/paper microchip is slid partially out of the housing, and 2 μL of sample (urine or whole blood) is dripped onto the sample injection zone. The chip is then slid back into the housing and the sample is filtered/separated by the paper strip and transferred under the effects of capillary action to the sealed paper-chip detection zone. The housing is inserted into the color analysis system and heated at 45 °C for 5 min to produce a purple-colored reaction complex. The complex is imaged using a CCD camera and the RGB color intensity of the image is then analyzed using a smartphone to determine the total protein (TP) concentration of the sample. The effectiveness of the proposed method is demonstrated using TP control samples with known concentrations in the range of 0.03–5.0 g/dL. The detection results obtained for 50 human urine samples obtained from random volunteers are shown to be consistent with those obtained from a conventional hospital analysis system (R2 = 0.992). Moreover, the detection results obtained for the albumin (ALB) and creatine (CRE) concentrations of 50 whole blood samples are also shown to be in good agreement with the results obtained from the hospital analysis system (R2 = 0.982 and 0.988, respectively).

An integrated microfluidic Au nanoparticle (AuNP) aptasensor device is proposed for monitoring the concentration of potassium (K

Sodium dehydroacetate (NADH) has good antibacterial effects and is widely used as a preservative in dairy products. However, NADH is toxic in large amounts, so it must be added to food in accordance with regulations. Accordingly, the current study has developed a microfluidic analysis detection (MAD) system for the determination of NADH in foods incorporating a microfluidic PMMA-paper chip and a smart analysis device. In this system, the extracted NADH sample is dropped into the sample chamber of the microfluidic PMMA-paper chip and is then wicking/filtering through paper strips and transferred to a detection zone embedded with Fe-Alum reagent. The chip is heated at 35 °C for 5 min to produce a compound reaction and the color compound image acquired by a camera is then transmitted wirelessly to a smartphone, where the NADH concentration is obtained by the intensity inversion of RGB analysis. A standard calibration curve is determined using NADH control samples with concentrations in the range of 30–5000 ppm. The feasibility of the proposed MAD system is then evaluated by analyzing the NADH concentrations of 15 commercial dairy products. It is shown that the measured values deviate from those obtained using an official high performance liquid chromatography (HPLC) method by no more than 5.0%.

This review reports on recent advances in state-of-the-art detection methods for microfluidic paper-based analytical devices (μPADs). The review commences by describing the materials, fabrication methods and driving mechanisms employed in μPADs. The review then explores the main detection methods and applications of μPADs proposed over the past five years. The discussions focus on seven detection technologies, namely (1) colorimetric detection, (2) fluorescent detection, (3) electrochemical detection and photoelectrochemical detection, (4) chemiluminescent detection, (5) electrochemiluminescent detection, (6) nanoparticle-based detection, and (7) spectrometry detection. Overall, the review provides a useful insight into recent advances in the μPAD detection field and serves as a useful source of reference for further research and innovation in the field.

An integrated platform consisting of a three-dimensional (3-D) microfluidic paper-based analytical device (µPAD) and a portable detection system is proposed for the determination of human whole blood creatinine. In the proposed detection method, the reaction region of the 3-D µPAD is implanted with picric acid and NaOH reagent and allowed to dry. Whole human blood is then dripped onto the inlet region of the chip and the blood plasma diffuses through the separation channel into the reaction zone under the effects of capillary action. The µPAD is heated at a temperature of 37 °C for 5 min to induce a Jaffe reaction between the creatinine in the blood plasma and the reagent. Finally, the creatinine concentration is detected using a colorimetric method. The validity of the proposed approach is demonstrated using control samples with creatinine concentrations ranging from 0.19 to 7.64 mg/dL. The detection results obtained for 40 real-world human serum creatinine samples and 30 real-world whole blood samples are shown to be in excellent agreement with those obtained using a conventional macroscale assay technique. Overall, the results show that the proposed platform provides a compact, low-cost and reliable approach for whole blood creatinine concentration detection.

Modern microflow cytometers are sophisticated instruments capable of measuring multiple physical characteristics of a single cell simultaneously as the cells flow in suspension through a measuring device. Cytometers are the tool of choice for the high-speed acquisition and analysis of large single cell populations. However, traditional devices lack the ability to provide intracellular spatial information. In the past few decades, various flow cytometer systems with the ability to combine cell/particle detection and the acquisition of two or three-dimensional spatial information have been proposed. However, these devices suffer a number of drawbacks Accordingly, the problem of developing more sophisticated microflow cytometers based on electrical impedance, optical detection and image analysis methods has received significant attention in the literature. This review describes some of the major advances made in the microfluidic cytometry field over the past ten years. The review focuses specifically on recent proposals for enhanced microfluidic focusing techniques and detection/analysis methods, respectively. Overall, the review provides a useful insight into the microflow cytometer technology field for both new and existing users.

This paper presents a review of the current state-of-the-art in micropumping technology for biomedical applications. The review focuses particularly on the actuation schemes, flow directing methods and liquid chamber configurations used in the devices proposed over the past five years. A comparative study is presented of the various mechanical and non-mechanical micropumps proposed for biomedical applications. The performance of the various devices is compared in terms of their actuation voltage, power consumption, operating frequency range, flow rate, backpressure, and so forth. The basic operating principles and advantages of each method are introduced, and their limitations described where appropriate. The review provides a useful source of reference for selecting micropumping schemes capable of meeting the specific flow rate requirements of different biomedical applications. In general, the review is expected to be of interest to both seasoned researchers and practitioners in the micropumping and biomedical technology fields and those entering the field for the first time.

Micromixers are crucial components within micro biomedical systems. This article presents a comprehensive review of the main state-of-the art applications of micromixers in biomedical systems over the past ten years. The article commences by reviewing the fundamental fluidic behaviors involved in microfluidic mixing. The biomedical applications of micromixers are then described in regard to their use particularly for (1) sample concentration, (2) chemical synthesis, (3) chemical reaction, (4) polymerization, (5) extraction and purification, (6) biological analysis, and (7) droplet/emulsion processes and others. The review concludes with a brief statistical analysis of the published literature in the micromixer field and an overview of the relative advantages of passive micromixers compared to active micromixers.

An integrated microfluidic loop-mediated isothermal amplification (LAMP) platform consisting of a microfluidic chip and a portable operating system is proposed for koi herpesvirus (KHV) detection applications. The microfluidic chip is fabricated using a CO2 laser system and comprises a sample chamber, two reagent chambers, a mixing chamber, a serpentine channel, a reaction chamber, and three flow rectifiers based on PDMS membranes. The main components of the operating system include a power source, a time relay, a microfluidic chip holder, four gas pressure valves, a microheater, and a temperature controller. In the proposed detection method, the KHV sample and LAMP reagent are loaded into the sample and reagent chambers, respectively, and are mixed under the effects of an external gas pressure driving force. The mixed solution is then heated at a temperature of approximately 63 °C for 60 min in order to replicate the KHV sample. Finally, the replicated sample is mixed with SYBR Green I dye in order to facilitate fluorescence-based KHV detection. The feasibility of the proposed microfluidic platform is confirmed by comparing the detection results obtained for a sample containing 10 ng/μL KHV with those obtained using a gel electrophoresis PCR-based method. The experimental results shows that the proposed LAMP platform has a KHV detection limit of around 3 × 10−2 ng/μL. Overall, the results presented in this study show that the proposed microfluidic platform provides a compact, reliable and portable tool for KHV detection purposes.

An integrated platform consisting of a microfluidic paper-based analytical device (μPAD) and a portable detection system is proposed for low concentration formaldehyde (CH 2 O) detection. In the proposed approach, the reaction zone of the μPAD is coated with ammonium acetate (AA) and acetoacetanilide (AAA) indicator and is dried at 40 °C for 30 min. The formaldehyde sample is then dripped on the reaction zone and the μPAD is transferred to a hot plate in the portable detection system. A Hantzsch reaction is induced by heating the μPAD at 30 °C for 10 min. The resulting fluorescent formaldehyde-Acetoacetanilide complex (dihydropyridine derivative) is observed by a CMOS camera and the color image is transferred to a smartphone by means of a connector. Finally, the CH 2 O concentration is derived using self-written RGB color analysis mobile software implemented on the phone. The experimental results obtained using control samples with known CH 2 O concentrations in the range of 0.2–2.5 ppm show that the B (blue) fluorescence intensity (Y) and formaldehyde concentration (X) are related as Y = 29.455 X + 117.64. Moreover, the correlation coefficient is equal to R 2 = 0.9937. The real-world applicability of the proposed detection platform is demonstrated by measuring the CH 2 O concentration in twelve commercial food samples. It is shown that the concentration measurements obtained using the proposed system deviate by no more than 6.2% from those obtained using a conventional spectrophotometric technique. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based system provides a compact and reliable tool for low concentration CH 2 O measurement purposes.

An integrated platform consisting of a microfluidic paper-based chip and a mini-box detection system is proposed for the concentration detection of formaldehyde. In the proposed approach, the reaction region of the paper-based chip is implanted with Acetoacetanilide reagent, and the formaldehyde concentration is deduced from the UV light-induced fluorescence intensity of the formaldehyde-Acetoacetanilide complex (dihydropyridine) produced in a Hantzsch reaction process at room temperature for 2 min. The experimental results obtained using control samples with formaldehyde concentrations ranging from 0 to 8 ppm show that the formaldehyde concentration (Y) and fluorescence intensity (X) are related as Y = 0.0039 e0.058X. Moreover, the correlation coefficient (R2) is equal to 0.9987. The real-world applicability of the proposed paper-based platform is demonstrated by measuring the formaldehyde concentration in eleven commercial food samples. It is found that the measurement results deviate from those obtained using a standard bench top method by no more than 4.7%. Overall, the results presented in this study show that the proposed system provides a rapid and reliable technique for formaldehyde concentration detection.

Cadmium exposure is associated with chronic kidney disease (CKD), but the optimal biomarker for early cadmium-associated nephrotoxicity in low-level exposure has not yet been established. We conducted a cross-sectional investigation involving 167 CKD patients stratified according to tertiles of urinary cadmium levels (UCd), in which enzyme-linked immunosorbent assay (ELISA)-measured novel renal biomarkers were utilized to assess the extent of renal injury associated with cadmium burden. In the analyses, urinary kidney injury molecule-1 (KIM-1) levels and age were the independent factors positively correlated with UCd after adjusting for covariates in non-dialysis-dependent CKD patients (high vs. low UCd, odds ratio (95% confidence interval), 1.0016 (1.0001–1.0032), p = 0.043, and 1.0534 (1.0091–1.0997), p = 0.018). Other conventional and novel renal biomarkers, such as serum creatinine, estimated glomerular filtration rate, CKD staging, urinary protein/creatinine ratio, urinary 8-hydroxy-2-deoxyguanosine (8-OHdG), and urinary epidermal growth factor (EGF) were not independently correlated with UCd in the analyses. In conclusion, our study found that the ELISA-measured urinary KIM-1 level could serve as an early renal injury marker in low-level cadmium exposure for non-dialysis-dependent CKD patients. In addition, age was an independent factor positively associated with UCd in this population.

Artificial sweeteners are often used by food manufacturers as a low-calorie alternative to sugar. However, an excessive consumption of artificial sweeteners can be harmful to human health. Consequently, their concentration in foods and beverages must be carefully controlled. The current study therefore proposes a microfluidic chromatography detection (MCD) system for the simultaneous concentration determination of two common sweeteners, namely saccharin sodium (SAC) and acesulfame potassium (Ace-K). In the proposed system, the sample is dropped on the MCD chip with a developing solution consisting of DI water, ethyl acetate, acetic acid and ethanol the chip is then placed in a UV microanalysis device. After allowing sufficient time for the developing solution to separate the SAC and Ace-K sweeteners from the interfering substances, the chip is illuminated by a 254-nm ultraviolet lamp and captured by a CMOS camera. Then wirelessly transfer the captured image to a smartphone, where the Ace-K or SAC sweetener concentration is derived using self-developed chromatography analysis app on the smartphone. Results obtained using control samples with known SAC and Ace-K concentrations show that the current MCD system provides a reliable detection performance for both sweeteners over the concentration range of 50 ~ 2000 ppm. Furthermore, the detection results of the concentrations of SAC and Ace-K in 16 commercial food samples are within 6.3% of the results obtained using traditional macroscale HPLC systems.

Pyroelectric infrared sensors incorporating suspended zinc oxide (ZnO) pyroelectric films and thermally insulated silicon substrates are fabricated using conventional MEMS-based thin-film deposition, photolithography, and etching techniques. The responsivity of the pyroelectric films is improved through annealing at a temperature of 500 °C for 4 h. The temperature variation and voltage responsivity of the fabricated sensors are evaluated numerically and experimentally for substrate thickness in the range of 1 to 500 μm. The results show that the temperature variation and voltage responsivity both increase with a reducing substrate thickness. For the lowest film thickness of 1 μm, the sensor achieves a voltage sensitivity of 3880 mV/mW at a cutoff frequency of 400 Hz. In general, the results presented in this study provide a useful source of reference for the further development of MEMS-based pyroelectric infrared sensors.

Microfluidic paper-based analysis devices (μPADs) have undergone tremendous development in recent years and now provide a feasible low-cost alternative to traditional laboratory tests for the diagnosis of many common diseases and disorders. As such, they are of great interest and importance in developing regions of the world with a lack of medical resources and associated infrastructures. This review examines the advances made in microfluidic paper-based diagnostic technology in the past five years and describes the application of microfluidic paper-based assays to the detection of many common human diseases using 3 non-invasive samples sources such as saliva, tears and sweat. The review commences by introducing the basic principles of fluid transport in microfluidic paper-based devices. The structures and actuation systems used in common paper-based devices are then introduced and explained. A systematic review of recent proposals for the application of paper-based devices to the diagnosis of common human diseases is then presented. The review concludes with a brief discussion of the challenges facing the microfluidics paper-based diagnosis field in the coming years and the emerging opportunities for future research.

A novel detection system consisting of a three-dimensional (3-D) sliding hybrid microchip (SHM) and a smart analysis device is presented to determine the phosphorus concentration in whole blood samples. The novelty of the SHM detection system includes filtering whole blood directly into serum, reacting different reagents in stages, performing a closed-type reaction to prevent evaporation of the test sample and uniform heating. The SHM is fabricated on PET and PMMA substrates and incorporates a sample injection zone, a filter paper-strip, two paper-chip reagent zones (reagent A and reagent B), and a detection zone. In the proposed detection method, 6 μL of whole blood sample is injected into the sample chamber and is filtered / separated by the paper-strip as it diffuses toward reagent zone A under the effects of capillary action. After 1 min, the sliding mechanism of the SHM is activated such that reagent zone B is positioned over reagent zone A in the detection/reaction zone. The SHM is then inserted into the smart analysis device and heated at 35°C for 4 min to prompt a modified molybdenum blue reaction. Finally, the blood phosphorus concentration is measured through a colorimetric method performed by a self-developed color analysis app installed on a smartphone. The feasibility of the current SHM detection system is demonstrated by the known control serum phosphorus concentrations ranging from 0.1–9 mg/dL. It is shown that the total R + B + G color intensity of the reaction complex image (Y) is linearly related to the serum phosphorus concentration (X) as Y = -31.502X + 600.740. The coefficient of determination (R2) and detection limit are 0.9936 and 0.06 mg/dL, respectively. The phosphorus concentration detection results obtained using the current SHM system for the whole blood samples of 100 real-world chronic kidney disease (CKD) patients are shown to be in excellent consistent with the detection results acquired through a macroscopic technique. Overall, the current SHM detection system provides a rapid and reliable method to detect the phosphorus concentration in whole blood samples.

Sodium benzoate (SBA) is a widely-used additive for preventing food spoilage and deterioration and extending the shelf life. However, the concentration of SBA must be controlled under safe regulations to avoid damaging human health. Accordingly, this study proposes a microfluidic colorimetric analysis (MCA) system composing of a wax-printed paper-microchip and a self-made smart analysis equipment for the concentration detection of SBA in common foods and beverages. In the presented method, the distilled SBA sample is mixed with NaOH to obtain a nitro compound and the compound is then dripped onto the reaction area of the paper-microchip, which is embedded with two layers of reagents (namely acetophenone and acetone). The paper-microchip is heated at 120 °C for 20 min to cause a colorimetric reaction and the reaction image is then obtained through a CMOS (complementary metal oxide semiconductor) device and transmitted to a cell-phone over a WiFi connection. Finally, use the self-developed RGB analysis software installed on the cell-phone to obtain the SBA concentration. A calibration curve is constructed using SBA samples with known concentrations ranging from 50 ppm (0.35 mM) to 5000 ppm (35 mM). It is shown that the R + G + B value (Y) of the reaction image and SBA concentration (X) are related via Y = −0.034 X +737.40, with a determination coefficient of R2 = 0.9970. By measuring the SBA concentration of 15 commercially available food and beverage products, the actual feasibility of the current MCA system can be demonstrated. The results show that the difference from the measurement results obtained using the macroscale HPLC method does not exceed 6.0%. Overall, the current system provides a reliable and low-cost technique for quantifying the SBA concentration in food and drink products.

Biochemical detection plays a critical role in many analytical fields. For example, blood samples include many proteins with relevance to disease diagnosis and therapeutic monitoring. Foods and beverages contain a large number of chemicals and compounds which must be quantified and characterized to ensure their compliance with safety standards. Detecting trace amounts of contaminants in ambient air or water samples is essential in monitoring the environment and protecting human health. Therefore, effective techniques for performing the rapid and reliable detection of targeted analytes are required. Compared to conventional macroscale devices, microfluidic systems have many advantages, including a greater sensitivity, a faster response time, a reduced sample and reagent consumption, and a greater portability. Accordingly, many microfluidic systems for sample detection have been proposed in recent years. The performance of such devices relies on the target analyte being present in a sufficient concentration to enable its detection. In many biomedical, food testing and environmental applications, the detection limit was restricted. Thus, the sample must first be concentrated before the detection process is carried out. Accordingly, this review provides a comprehensive review of recent advances for sample preconcentration with emphasis on utilizing ion concentration polarization (ICP) effects in micro/nanofluidics platforms. We start with a brief introduction regarding the importance of preconcentration using micro/nanofluidics platforms, followed by in-depth discussions of the ICP effects for the preconcentration and applications to biomedical analysis, food testing and environmental monitoring. Finally, the article concludes with a brief perspective on the future development of the field.

An integrated platform consisting of a microfluidic paper-based/PMMA (Polymethyl-Methacrylate) chip and a small battery-operated detection system is proposed for the concentration detection of sulfur dioxide (SO 2 ). In the proposed method, a small strip of filter paper is coated with acid-base indicator and then inserted into a PMMA microchip. The SO 2 sample is then injected into the reservoir of the chip; prompting a reaction with the acid-base indicator. The chip is transferred to the detection system, where the reaction-induced color change is captured by a CMOS (Complementary Metal-Oxide Semiconductor) camera. Finally, the CMOS image is transferred to a cell phone via a USB (Universal Serial Bus) connector and the SO 2 concentration is derived using self-written RGB color analysis software. The experimental results obtained for 10 control samples show that the correlation coefficient for the variation of the R(ed) signal intensity with the SO 2 concentration is equal to R 2 = 0.9971 in the low-concentration range (20 ∼ 600 ppm) and R 2 = 0.9920 in the high-concentration range (600 ∼ 5000 ppm). The real-world applicability of the proposed platform is demonstrated by measuring the SO 2 concentrations of fifteen commercial food samples. The concentration measurements deviate by no more than 4.29% from those obtained using a standard macroscale technique. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based system provides a cheap, compact and reliable method for SO 2 concentration measurement purposes.

Distillation is a powerful technique for separating the component substance from a miscible fluid mixture by means of selective evaporation and condensation. Distillation is of importance in many microfluidic applications, including food processing, gas/liquid separation, and biochemical. However, at the microscale, surface tension forces exceed gravitational and hydrodynamic forces, and hence traditional gravity-based distillation methods have only a limited efficiency. Consequently, various alternative methods for separating miscible fluid mixtures at the microscale have been proposed in recent years based on techniques such as vacuum forces, capillary forces, centrifugal forces/gravity effect, other types, and so on. The main developments in the micro-distillation field are introduced and discussed in the present review.

A micro-distillation system is presented for formaldehyde concentration detection in food products. The proposed system consists of a micro-distillation device, a micro-condensed device, micro-distillation chip, a high-pressure steam tank, a temperature controller, and a cooling system. The distillation chip is fabricated on polymethylmethacrylate (PMMA) substrates using a CO2 laser system and comprises three distilling chambers, a condenser micro-channel and a cooling micro-channel. In the proposed system, the formaldehyde sample is injected into the distillation chip and a high-pressure steam supply is used to vaporize the formaldehyde and carry it to the condenser region of the chip. The formaldehyde vapor is condensed under the effects of the low-temperature cooling channel and is transported to the collection region of the device. Finally, a colorimetric detection process is performed to measure the formaldehyde concentration of the collected sample using a commercial spectrophotometer. The validity of the proposed system is investigated using a control sample with a formaldehyde concentration of 6 ppm. It is shown that a distillation efficiency as high as 98% can be obtained given a steam pressure of 4 bar. The real-world applicability of the proposed micro-distillation system is demonstrated by measuring the formaldehyde concentrations of 18 commercial Chinese herb samples.

A multifunctional microchip-based distillation apparatus for distilling and detecting formaldehyde (CH2O) in food products is developed. The presented apparatus comprises a disposable microchip, a steam supply system, and a recirculating cooling water supply. The microchip is formed on PMMA substrates by laser ablation and includes a sample zone, a flash distillation zone, a cooling zone, a condensation zone, and a collection zone. In the presented method, the CH2O sample is placed in the microchip and is vaporized by the high-throughput vapor supply and driven through the condensed zone. The condensed CH2O liquid is guided into the collection zone of the microchip. Finally, the distilled CH2O solution is determined using an AHMT spectrometry method and a paper-based RGB (red, green and blue) intensity analysis method. A distilled efficiency is as high as 98%, when a vapor stream rate is 0.4 ml/min and a distilled time is 10 min. Moreover, both detection methods show linear relationships of the corresponding CH2O concentrations. The actual sample suitability of the presented multifunctional microchip-based distillation apparatus is confirmed by analyzing the CH2O concentrations of 21 commodities.

Nanomaterials have attracted significant attention in biomedical and environmental science in recent years due to their unique thermal, optical, electrical and magnetic properties. The properties of nanomaterials are highly correlated with their size and morphology. Consequently, efficient methods for synthesizing nanomaterials with a consistent size and shape are urgently required. Compared to conventional large-scale synthesis systems, microfluidic systems offer a far better control over the growth, nucleation and reaction conditions. As such, microfluidic synthesis has emerged as a key enabling technology for the rapid, low cost and reliable preparation of nanomaterials with complex properties and functions. This review provides a detailed overview of advances in the microfluidic synthesis technology field over the past five years. The review commences by describing the main microfluidic control mechanisms and microfluidic synthesis of particles. Some of the more common applications of microfluidic synthesized micro and nanomaterials are then introduced, including drug delivery, bioimaging, biosensing, environmental analysis, and cell analysis. The review concludes with a brief overview of the challenges facing the microfluidic synthesis field in the coming years, together with possible research directions aimed at overcoming these challenges.

The aim of microfluidic mixing is to achieve a thorough and rapid mixing of multiple samples in microscale devices. In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows. Passive micromixers utilize no energy input other than the pressure head used to drive the fluid flow at a constant rate. Under such conditions, the flow has a laminar characteristic, and hence mixing relies mainly on the induction of a chaotic advection effect to increase the contact surface and contact time between the species flows. Many passive mixers have been proposed to facilitate this task over the past five years. The details of these mixers are briefly described in the following review.

Ferrofluids have many traditional applications in the electrical, mechanical and optical fields, including transformers, dampers, imaging systems, and so on. However, in more recent years, the potential provided by ferrofluids to manipulate tiny quantities of liquid by means of external magnetic fields has attracted great interest in the microfluidics domain; resulting in the emergence of a new branch of scientific known as micro-magnetofluidics. This study reviews recent applications of micro-magnetofluidics techniques to six common microfluidic functions, namely micromixing, pumping, focusing, sorting, droplet formation and transfer phenomena. For each function, the fundamental interaction mechanisms between the ferrofluid and the magnetic field are described and the main experimental and numerical results are discussed.

A novel micropump is proposed comprising a PMMA-based rotor, a circular PDMS micro-chamber, and a semi-circular PDMS microchannel connecting the inlet and outlet reservoirs as the rotor spins, a plug of sample fluid is trapped within the microchannel between neighboring blades of the rotor and is driven through the channel toward the outlet. Meanwhile, the rotors periodically compress and release the inlet and outlet regions of the microchannel. Thus, as the rotor turns, one plug of sample fluid is drawn into the microchannel as another is ejected into the outlet reservoir. In other words, a peristaltic pumping effect is achieved. It is shown that the flow rate in the proposed device can be controlled simply by adjusting the rotational velocity of the rotor. A maximum flow rate of 1.22 ml/min is obtained given de-ionized water as the working fluid and a rotational velocity of 232 rpm. Moreover, given the same rotational velocity, flow rates of 0.724 ml/min and 0.336 ml/min are obtained for salad oil and engine oil, respectively.

A microfluidic colorimetric system comprising of a colorimetric paper-chip device and a microanalysis cassette is presented for detecting the nitrite concentration in foods. In the proposed system, 1 μl of nitrite sample is dropped into the reaction region of the colorimetric paper-chip device, where its reacts with embedded Griess reagent to produce a pink complex. A color image of the reaction complex is caught using an embedded camera and transmitted to a cell phone within the microanalysis cassette via a WiFi connection. Finally, the images were analyzed by self-written RGB (Red, Green, and Blue) software to evaluate the nitrite concentration. The results acquired for 11 known nitrite solutions ranging from 1 to 100 ppm show that the measured R + G + B intensity is related to the nitrite concentration, and the determination coefficient (R2) are 0.9908 and 0.9948 in the two concentration ranges of 1–50 ppm and 50–100 ppm, respectively. The practical feasibility of the current microfluidic system is indicated by analysis the nitrite concentrations of 24 actual samples. Therefore, the difference between the concentration analysis obtained with the current system differ from those obtained using a conventional TFDA (Taiwan Food and Drug Administration) standard method by no more than 7.3%. Furthermore, the detection limit is just 1 ppm.

A microfluidic detection platform is presented for the rapid and low-cost measurement of preservatives in foods. The microfluidic platform consists mainly of an integrated microfluidic reaction chip and a micro-spectrometer detection system. The reaction chip further involves a heater and a micromixer zone for sample/reagent mixing and reaction, and is fabricated on a PMMA substrate using a CO2 laser. The feasibility of the presented platform is confirmed by measuring the concentration of sorbic acid in food samples. In the analysis process, the extracted sample is mixed with Iron(III) reagent and Thiobarbituric acid (TBA) by a gas driving force and a colorimetry reaction (oxidation reaction) of the mixture (pink complex) is then caused by a micro-heater system. The pink complex is driven to the detection chamber of the microfluidic reaction chip, where it is analyzed by the micro-spectrometer system under illumination of a 530 nm (wavelength) LED light source. Finally, the sorbic acid concentration is derived from the measured value using a calibration curve constructed on the basis of seven sorbic acid control samples with known concentrations ranging from 0.02–0.5 g/kg. The results indicated that the sorbic acid concentration detections of the 15 commercial samples obtained using the presented platform differed from the detections obtained using a standard macroscale HPLC method by no more than 7.5%. In a further series of tests, the determination coefficients for benzoic acid, sulfur dioxide and formaldehyde are found to be R2 = 0.9961, 0.9933 and 0.9968, respectively. In other words, the general feasibility of the proposed platform for preservative detection in foods is confirmed.

In the study, a novel micro impedance inclinometer is presented, consisting of a glass substrate, Cr electrodes and a mercury pendulum. The output signal of the proposed inclinometer is read from the moving metal pendulum based on an LED array measurement scheme. A mercury pendulum mass is used for the inclinometer. The adhesion between the liquid metal and the substrate surface is reduced by etching or sandblasting the substrate surface. Experimental results show the developed inclinometer has a high angle resolution (0.3°), a rapid time response (385 ms) and a high repeatability (R2 = 0.9988) with the A280# sandblasted substrate surface and the mercury pendulum of 360 μl. The developed inclinometer provide a simply yet high-performance solution for the inclination measurement.

Microfluidic paper-based analytical devices (μPADs) have experienced rapid growth over the past decade due to their simple design, low cost, minimal sample requirement, and good sensitivity, selectivity and accuracy. While designed originally for point-of-care medical diagnostics, biological, and food safety applications, μPADs are now used increasingly for environmental monitoring purposes. This review provides a detailed overview of the μPADs developed over the past ten years for the environmental analysis of soil, air, ecology (pesticides) and river water. The review commences by introducing the fabrication techniques and detection methods used in μPAD technology. A detailed description of the main μPAD frameworks proposed in the past decade for environmental monitoring is then provided. The review concludes by examining the challenges facing μPADs for environmental monitoring and identifying probable avenues of future research.

An integrated microfluidic platform comprising a microfluidic paper-based analytical device (µPAD) and a portable detection system is proposed for the concentration detection of benzoic acid via Janovsky reaction theory. In the proposed approach, the reaction zone of the µPAD is implanted with 5 N sodium hydroxide and dried at 30 °C for 20 min. The benzoic acid sample is derived to 3,5-Dinitrobenzoic acid using KNO3 and H2SO4 at 40 °C for 40 min and is then dripped on the reaction zone of the µPAD. Finally, the µPAD is transferred to the portable detection system and heated at a temperature of 45 °C for 20 min on a hot plate to prompt a Janovsky reaction. The resulting color change of the detection zone is observed using a CMOS camera. The reaction color image is delivered to a smartphone via a connector and the benzoic acid concentration is determined using self-written RGB analysis software. The experimental results obtained using control samples with known benzoic acid concentrations in the range of 500–4000 ppm show that the R(ed) + B(lue) intensity (Y) and benzoic acid concentration (X) are related as Y = −0.0264 X + 408.79. Moreover, the correlation coefficient is equal to R2 = 0.9953. The proposed detection platform is used to measure the benzoic acid concentrations of twenty-one commercial food samples. It is shown that the concentration measurements deviate by no more than 6.6% from those obtained using a standard HPLC macroscale method. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based chip platform provides a compact and reliable tool for benzoic acid concentration measurement purposes.

A novel vortex micromixer is proposed comprising an injection channel (Y-shaped or Interlaced-shaped), a nozzle structure and a double-heart mixing chamber. In the proposed device, the species are loaded into the injection channel and undergo an initial mixing effect as a result of natural diffusion. The partially-mixed species are then passed through the nozzle structure into the double-heart chamber, where they are further mixed by symmetrical rotating vortex structures before flowing into the exit channel. The flow phenomena and species concentration distributions within the nozzle structure and double-heart mixing chamber are evaluated by means of numerical simulations. The numerical results are confirmed by performing flow visualization experiments. It is shown that the mixing ratio in the Interlaced-shaped micromixer reaches 92% even at Reynolds numbers as low as Re = 1 given a nozzle ratio of 0.25. Overall, the results presented in this study show that the proposed vortex micromixer provides a simple yet effective solution for mixing problems in the micro-total-analysis systems (μ-TAS) field.

An integrated platform comprising a PMMA (Polymethyl-Methacrylate) microfluidic array chip and a LED photometer system is proposed for the concentration detection of sulfur dioxide (SO 2 ) and methanol (CH 4 O). In the proposed device, the sample and reagent are injected into six open chambers on the microfluidic chip and are mixed via a vortex stirring effect. Following the mixing process, a colorimetric reaction is induced between the sample and the reagent by means of a microhotplate positioned beneath the microfluidic chip array. The microfluidic chip is then transferred to a LED photometer system for detection purposes. The experimental results show that correlation coefficients of R 2 = 0.9915 and R 2 = 0.9941 are obtained when plotting the photometer output voltage against the SO 2 and CH 4 O concentrations of control samples with known concentrations ranging from 50 to 500 ppm. The real-world applicability of the proposed experimental platform is demonstrated by measuring the SO 2 concentration in two commercial Chinese herbs and the CH 4 O concentration in two commercial wines. It is shown that the concentration measurements obtained using the proposed system deviate by no more than 9% from those obtained using standard macroscale methods. Overall, the results presented in this study show that the proposed integrated microfluidic platform provides a compact and reliable tool for SO 2 and CH 4 O concentration measurement purposes.

A novel integrated microfluidic chip with a three-layer polymethyl methacrylate (PMMA) structure is proposed for formaldehyde concentration detection applications. In the proposed device, the sample and a fluorescence derivatization reagent (Fluoral-P) are mixed in a circular mixing chamber and then flow through a serpentine reaction channel heated to a temperature of 30 °C by an integrated hotplate. Following a reaction time of 4 min, the microchip is removed from the hotplate and placed in the microscope stage of a laser-induced fluorescence (LIF) detection system. The formaldehyde concentration of the sample is then inversely derived from the measured value of the fluorescence intensity. The validity of the proposed device is confirmed by comparing the detection results obtained for standard samples with known formaldehyde concentrations ranging from 1 to 50 ppm with those obtained using a traditional UV/VIS absorption spectrometry. The real-world applicability of the proposed device is then demonstrated by measuring the formaldehyde concentration in ten commercial Chinese herbs. It is shown that the measurement results deviate by no more than 3.7% from those results obtained using colorimetric method by CAAPIC. Overall, the results presented in this study show that the proposed microchip provides a rapid and reliable tool for formaldehyde concentration measurement purposes.

Electric field is the method of choice in microfluidic devices for precise transport and placement of particles via fluid electroosmosis and particle electrophoresis. However, current studies on particle electrophoresis in microchannels have been focused mainly upon Newtonian fluids though many of the chemical and biological fluids possess non-Newtonian characteristics. Especially lacking is the experimental study of particle electrophoresis in either type of fluids. We report in this work an unprecedented experimental observation that polystyrene particles migrate towards the walls of straight rectangular microchannels in the electroosmotic flow of shear-thinning xanthan gum (XG) solutions. This phenomenon is opposite to the particle focusing along the channel center in our control experiment with the Newtonian base fluid of the XG solutions. It is attributed to a fluid shear thinning-induced lift that overcomes the wall-induced repulsive electrical lift. The parametric effects of the fluid-particle-channel-(electric) field system are systematically investigated.

The subject of study in this work is a 135 Wp high concentration photovoltaic module with III-V solar cells. The module is currently installed in NPUST. Three equation forms for module temperature prediction were investigated. The simplest form predicts the module temperature quite well. Among these forms, the third form which takes into account the direct normal radiation yields the least error. The efficiency of the module was about 21% between 10:00 a.m. and 3:00 p.m. and the amount of power the module generates was linearly dependent on the electricity current.

A method is proposed for detecting microparticles in a microflow cytometer by means of small angle forward-scattered light measurements. The proposed cytometer comprises a commercial photovoltaic cell, an adjustable power laser module, and a PDMS microfluidic chip. The detection performance of the proposed device is evaluated using particles with dimensions of 5, 8, 10, and 15 μm, respectively, given forward-light scattering angles of 5 and 8° and laser powers ranging from 15-25 mW. It is shown that for a constant laser power and particle size, the S/N of the detected light signal increases with a reducing forward-scattering angle. Moreover, for a constant forward-scattering angle and particle size, the S/N increases with an increasing laser power. The intensity of the forward-scattered light signal is found to vary linearly with the particle size and has a correlation coefficient of R(2) = 0.967, 0.967, and 0.963 given laser powers of 15, 20, and 25 mW, respectively, and a forward-scattering angle of 5°. Moreover, the CV of the forward-scattered light intensity is found to lie within the range of 20-30% for both forward-scattering angles. Overall, the present results suggest that the proposed device has significant potential for detection applications in the medical, environmental monitoring, and biological science fields.