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Subject: search.filters.subject.On-site detection

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    Dip-to-detect electrochemical microfluidic device: Integrating sample collection and automated mixing for on-site detection of heavy metals
    (2026-02-01)
    Khamcharoen, Wisarut
    ;
    Jaewjaroenwattana, Jutamas
    ;
    Wajasen, Kwanchanok
    ;
    Naorungroj, Sarida
    ;
    Jampasa, Sakda
    Human exposure to heavy metals poses a global threat due to their harmful health and environmental effects. Standard analytical methods rely on complex operations and sophisticated instruments, making them costly, labor-intensive, and limited in on-site suitability. This work presents a “dip-to-detect” electrochemical microfluidic device that enables direct sample dipping and automated electrolyte mixing. The device is made using stacked layers of transparent and double-sided adhesive films designed to enable sequential flow control. We implement a fluid-triggered valve to allow direct dipping and store the sample solution inside the channel without leakage. The electrolyte is added to the device without fixed-volume pipetting, activating the valve for rapid mixing with the sample solution. The device is equipped with a near field communication (NFC) controlled potentiostat for the portable detection of Cd(II) and Pb(II) with limits of detection of 90 ppb and 80 ppb, respectively. To validate its performance, the microfluidic device was tested with spiked industrial water samples. The device demonstrated good recovery, ranging from 102.2 % to 116.7 %. The dip-to-detect electrochemical microfluidic device eliminates the need for pipetting and manual mixing. This platform introduces a new alternative for field-deployable sensing and has the potential to inspire future designs focused on simple sample collection, automated reagent handling, and minimal user intervention.
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    On-site microfluidic paper- based titration device for rapid semi-quantitative vitamin C content in beverages
    (2021-05-01)
    Kaewchuay, Netnapit
    ;
    Jantra, Jongjit
    ;
    Khettalat, Chanyaphon
    ;
    Ketnok, Supansa
    ;
    Peungpra, Naruemon
    A rapid, simple and on-site redox titration of vitamin C was accomplished using a novel microfluidic paper-based analytical device. The analysis was based on the combination of traditional redox titration and a microfluidic paper-based titration. The device was designed to have one sample zone connected to a titrant zone where ten different concentrations of iodine (titrant) were filled in each well. The top part of the device was a detection zone where the starch solution (indicator) was added. Vitamin C was added into a sample zone and then flowed to the titrant zone where the vitamin C was oxidized by the iodine. The excess iodine reacted with the starch indicator and endpoint of titration was reached when the blue-black product was observed by the naked eye in the detection zone. The proposed method for vitamin C detection showed the working range between 2.5 and 1,000 mg/L. The limit of detection was 2.5 mg/L. Time for an assay was only 3 sec. The developed paper-based device was applied to detect vitamin C in the real sample of beverage and the results corresponded to those obtained from traditional redox titration. The developed assay proved to be less reagent consumption compared to the traditional one. It is a truly portable device with no glassware and skilled personnel to require.
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