Chitosan-modified cotton thread for the preconcentration and colorimetric trace determination of Co(II)

In this work we propose a thread-based microfluidic device (μTAD) for the preconcentration and colorimetric determination of Co(II) in water using a digital image. The reaction is based on complexation of Co(II) by 4-(2- pyridylazo) resorcinol (PAR), which changes the detection zone from yellow to red. PAR is immobilized in a chitosan membrane to retain the complex in the detection zone. The designed μTAD makes it possible to pre- concentrate and determine cobalt between 25 and 600 µg·L−1 with a relative standard deviation of 4% (n = 5), and a detection limit of 6.5 µg·L−1. The device permits an enhancement factor of 11 by combining the use of a chitosan retention membrane and a sample volume of 50 µL. Recovery experiments were performed in tap water to evaluate the accuracy of the method, and the results obtained compared to a reference method presents an error no higher than 5.7%This work was founded by Spanish “Ministerio de Economía y Competitividad” under Project CTQ2016-78754-C2-1-R and Junta de Andalucía under Projects B-FQM-243-UGR18 and P18-RT-2961. The project was partially supported by European Regional Development Funds (ERDF). Supporting Research in the State of Minas Gerais (Fapemig) (CEX-APQ-02436-15)

Multiple semi-quantitative colorimetric assays in compact embeddable microfluidic cloth-based analytical device (mu CAD) for effective point-of-care diagnostic

Cotton fabric is proposed as an alternative material for low-cost point-of-care devices. Cotton fabrics are vastly available, low cost and flexible. Simple wax patterning method was applied to create hydrophilic channels in cotton fabric. Three-dimensional (3D) colorimetric microfluidic device was made by folding 2D pattern along certain predefined lines. Three-dimensional devices show better mixing uniformity between reagents and analyte across the detection zones. On-chip colorimetric calibration is also proposed by putting predefined serially diluted samples next to the detection zones. Multiple assays can be integrated within a small surface area by stacking layers of individual assay device separated by a wax-impregnated fabric. We were able to detect glucose, nitrite and protein having concentration as low as 0.5 mM, 30 μM and 0.8 mg/mL, respectively, by bare eyes. Results of the assays from an unknown analyte sample and precalibrated serially diluted sample standards were displayed in a side-by-side configuration, and the interference of each analyte on the other reaction zones was investigated. These results are better than if the detection is merely taken from the calibration curve without integrated standard calibration. The mechanical durability, robustness and flexibility of 3D microfluidic cloth-based analytical device (μCAD) also make it easily embeddable to daily wearable product. We demonstrated multiple single-step qualitative assays using embedded 3D μCAD and propose a new concept of “point-of-sampling diagnostic”

"Periodic-table-style" paper device for monitoring heavy metals in water

If a paper-based analytical device (mu-PAD) could be made by printing indicators for detection of heavy metals in chemical symbols of the metals in a style of the periodic table of elements, it could be possible for such mu-PAD to report the presence and the safety level of heavy metal ions in water simultaneously and by text message. This device would be able to provide easy solutions to field-based monitoring of heavy metals in industrial wastewater discharges and in irrigating and drinking water. Text-reporting could promptly inform even nonprofessional users of the water quality. This work presents a proof of concept study of this idea. Cu(II), Ni(II), and Cr(VI) were chosen to demonstrate the feasibility, specificity, and reliability of paper-based text-reporting devices for monitoring heavy metals in water

Bilayer graphene nanoribbon mobility model in ballistic transport limit

Bilayer graphene nanoribbon (BGN) with tunable band gap which can be controlled by an external electric field is focused in our study. AB-stacked system with a stable structure is considered in a FET channel. Based on the assumed structure carrier density effect on charge mobility has been reported at different temperatures. Carrier mobility model is explained based on quantum confinement effect which indicates that carriers behave like traveling wave only in channel direction. Their behavior in other two directions can be approximated by standing wave as well. We prove that carrier mobility in BGNs is a function of temperature and carrier density which illustrate good agreement with experimental data

Advancements in magnetic aptasensors: Recent progress and future trends in biosensor technology

Advancements in magnetic aptasensors: Recent progress and future trends in biosensor technolog

Surface modification of cellulose paper for quantum dot-based sensing applications

Cellulose paper specimens with and without surface modification were compared in order to study their physicochemical compatibility with quantum dots (QDs) for biochemical sensing applications. Silane and chitosan modification methods were applied. The distribution of QDs deposited on untreated paper and papers modified with silane and chitosan were investigated in order to understand the interaction between QDs and fibre. Modified papers were shown to significantly reduce the undesirable redistribution of QDs during paper drying. The retention ability and thermal resistance of QDs to the loss of fluorescence on modified papers were also studied for the purpose of determining the most suitable paper surface modification for developing QD-Paper-based analytical devices (QD-PADs). Furthermore, chitosan-modified paper was used to design QD-PADs to quantify glucose concentration in aqueous samples; the quenching effect of the enzymatic product on the fluorescent emission of QDs was used as the indicator system. The change of fluorescence of QDs was measured by a simple in-house constructed fluorescence imaging system. The detection limit of glucose was 5 mg/dL, which is comparable with other reported paper sensors for detection of glucose

Understanding thread properties for red blood cell antigen assays: Weak ABO blood typing

Thread-based microfluidics research has so far focused on utilizing and manipulating the wicking properties of threads to form controllable microfluidic channels. In this study we aim to understand the separation properties of threads, which are important to their microfluidic detection applications for blood analysis. Confocal microscopy was utilized to investigate the effect of the microscale surface morphologies of fibers on the threads separation efficiency of red blood cells. We demonstrated the remarkably different separation properties of threads made using silk and cotton fibers. Thread separation properties dominate the clarity of blood typing assays of the ABO groups and some of their weak subgroups (Ax and A3). The microfluidic thread-based analytical devices (μTADs) designed in this work were used to accurately type different blood samples, including 89 normal ABO and 6 weak A subgroups. By selecting thread with the right surface morphology, we were able to build μTADs capable of providing rapid and accurate typing of the weak blood groups with high clarity

Self-operating seawater-driven electricity nanogenerator for continuous energy generation and storage

The ubiquitous and continuous natural processes of water absorption and evaporation have stimulated interest in generating electricity through the creation of a flow of electrical charge, which can then be collected and stored. However, the resultant low output power density as well as the complicated fabrication and operation processes have hindered the practical applications of this technology. Herein, we demonstrate a highly efficient self-operating hydroelectric nanogenerator (HENG) that produces electricity through the absorption and evaporation of seawater. The single HENG consists of a hydrophilic wool cloth stripe functionalized with ketjen black powders and equipped with two electrodes affixed at its ends. The continuous absorption and evaporation of seawater results in the generation of electricity that can be stored in a capacitor. A series of 16 HENGs, each consisting of 10 stacked wool cloth stripes, can generate sufficient power to charge a supercapacitor to 1.6 V within 5 h 30 min under ambient conditions, outperforming most comparable devices reported. The superior performance observed for the HENG is attributable to the hydrophilicity and porosity of wool cloth which can continuously absorb seawater at a desired rate as well as the 2D structure of ketjen black and its high conductivity. This work paves the way to facilitate the development of HENGs for practical applications

Définition et identification des tables de nomenclatures

International audienceDans une base de données relationnelle, certaines tables ont pour finalité de rassem- bler et d’apporter des informations complémentaires aux lignes des tables constituant le coeur de la base. Ces données sont stockées dans des tables que nous désignons “tables de nomen- clatures”. Pouvoir les distinguer présente de nombreux intérêts dans le cadre de l’étude, la maintenance et l’évolution d’une base de données. Nous proposons des propriétés permettant de définir la nature de ces tables. Une expérience permettant de valider les propriétés propo- sées est décrite puis appliquée à un cas d’étude. Un modèle de classification pour les tables de nomenclatures est construit à l’aide d’un algorithme d’exploration de données (datamining). Son évaluation montre une précision 88, 6% et un rappel de 88, 7%.ABSTRACT. In a relational database, some tables are used to gather additional information to rows of tables forming the core of the database. This data is stored in tables that we call “no- menclature tables”. Being able to distinguish them offers many interests in the study, mainte- nance and evolution of databases. We propose properties to define the nature of these tables. Then, an experiment to validate the proposed properties is described and applied on a case study. A classification model for nomenclature tables is built using a datamining algorithm. Its evaluation shows a precision of 88.6% and a recall of 88.7%