Recently, the concentration of 〖CO〗_2, one of the major air pollutants for greenhouse effect, is increasing due to the massive use of fossil fuels. Thus, research about gas sensors for monitoring 〖CO〗_2 gas have performed, and conventional methods have the challenge of requiring complex structures. Thus, research about gas sensors using nanomaterials has been conducted, and graphene-based gas sensors have been actively researched since its extraordinary conductivity. However, there are challenges that the gas absorption site is limited in chemically unstable site. In this study, ZnO/graphene heterostructure to improve the gas absorption area with high conductivity through ZnO on graphene was presented. Each layer acted as a gas adsorption and a carrier conducting layer respectively, and the sensitivity by the thickness of ZnO and the effect of the annealing temperature were evaluated. This work exhibited a sensitivity of 78% at room temperature, and repeatability and selectivity were also studied.
Phosphorus (P) is one of the most important elements in the aquatic ecosystem, but its overuse causes eutrophication, which is a serious issue worldwide. In this study, we developed a miniaturized portable total phosphorus (TP) analysis device by integrating a TP sensor with a photocatalyst to pretreat analyte and optical components (LED and photodetector) to measure the absorbance of the blue-colored analyte for real-time TP monitoring and prevention of eutrophication. The size of the miniaturized portable TP analysis device is about 10.5 cm × 9.5 cm × 8 cm. Analyte-containing phosphorus was pretreated and colored blue by colorizing agent as a function of the phosphorus concentration. Absorbance of the blue-colored analyte was estimated by the LED and the photodetector such that the phosphorus concentration was quantitatively measured. This device can obtain a wide linear response range from 0.5 mg/L to 2.0 mg/L (R2 = 0.97381), and its performance can be improved by increasing the intensity of the UV light emitted from the LED array. Consequently, the performance of this miniaturized portable TP analysis device was found to be similar to that of a conventional TP analysis system; thus, it can be used in automated in situ TP analysis.
We presented microfluidic resistive pulse sensing for submicron particles and exosomes with high sensitivity via multiple gates and gate structure modification.
With introducing the possibility of early diagnosis through biomarker detection, this method has become important in the field of disease diagnosis. Particle sorting based on conventional digital microfluidics (DMF) mostly employs magnetic beads. In this study, the micropillar-based DMF device confirmed the ability of microbead filtering to detect specific biomarkers. The proposed device was implemented using micro-electromechanical systems, and SU-8 micropillar was realized based on the micro-patterning technology. DMF was able to control droplet movements considering the principle of electrowetting on dielectric. The moving speed of a droplet varied according to the electrode shape and applied voltage. As the droplet moved, the polystyrene bead was sorted corresponding to the interval of the fabricated SU-8 micropillar.
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