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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.

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 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.

Revealing the spatial and temporal distribution of bacteria in organic tea plantations is of great importance to clarify soil- and/or tea plant-associated community. In this study samples were collected from three rhizo-compartments of tea plant during four seasons, which were further subjected to community level physiological profiling and 16S rDNA next generation sequencing. Organic fertilization caused a short-term disturbance on pH, EC, and organic matter content of soil. Three rhizo-compartments harbored distinct bacterial community as revealed by PCA, PCoA and UPGMA analysis. Utilization of six carbon source categories was positively correlated with root surface community while negatively correlated with root interior community. Although there were variations in microbial parameters during four seasons, higher metabolic potential and diversity were observed in soil-associated rhizo-compartments. Bacterial families Gemmataceae, Pedosphaeraceae, and Solibacteraceae were more abundant in soil and root surface, while root interior were dominated by families Acidothermaceae, Burkholderiaceae, Ktedonobacteraceae, and Xanthobacteraceae. It is proposed that Burkholderiaceae and Xanthobacteraceae which dominate in root surface or root interior samples and other poorly studied phylogenetic groups may serve as potential candidates to study their interaction with tea plant.

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.

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.

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.