Microfluidic Dean-flow enhanced electrochemical detection of lead in water

We present a cost-effective microfluidic electrochemical sensor (MES) that operates without electrode surface modification, utilizing curved microchannels to promote efficient analyte transport and enhance electrochemical sensing via Dean flow. Despite significant progress in MESs for lead (Pb) detection, current designs often rely on complex and costly fabrication, as well as environmentally taxing surface modifications. Additionally, the use of laminar flow-based straight microchannels limits mass transport and sensor sensitivity. The present MES was fabricated using pressure-sensitive adhesive and polyethylene terephthalate sheets via laser machining. Square wave voltammetry and square wave anodic stripping voltammetry were employed to evaluate the performance of the curved-channel MES.

The sensor achieved a Pb²⁺ limit of detection (LOD) of 2.26 μg/L, meeting the regulatory limits set by Health Canada and the U.S. Compared to the straight-channel MES, the curved-channel design showed a 66-fold increase in sensitivity and a 75-fold reduction in LOD, attributed to enhanced analyte transport via Dean flow. Further experiments with Cadmium (Cd) in water showed Cd²⁺ LOD of 38.3 μg/L, showcasing the expandability of the sensor to other heavy metals. Additionally, the MES demonstrated Pb²⁺ selectivity in the presence of interfering ions, including Cd²⁺, Cu²⁺, Zn²⁺, Fe³⁺, and Mn²⁺. Real water sample analysis confirmed the sensor's practicality in complex matrices, reinforcing its utility for real-world applications.

Results demonstrate that the proposed curved-channel MES enables reliable, modifier-free, and scalable detection of Pb²⁺, even in complex water matrices, offering strong potential for expansion to other heavy metals detection in water.