Dip-to-detect electrochemical microfluidic device: Integrating sample collection and automated mixing for on-site detection of heavy metals

Abstract

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.