A highly sensitive, easy-and-rapidly-fabricable microfluidic electrochemical cell with an enhanced three-dimensional electric field

Abstract

An NP-μFEC is a reusable, novel microfluidic electrochemical cell with multiple non-planar interdigitated microelectrode arrays, minimal sample volume, and enhanced electric field penetration for highly sensitive electrochemical analysis. (i) The NP-μFEC features spatial 3-electrode architecture, and a small sample volume (∼4 μL). (ii) Here, [Fe(CN)6]3-/4- redox couple are used as an electrochemical reporter. The effects on the electrochemical properties of NP-μFEC due to the change in the reference electrode (RE) and counter electrode (CE)'s position with respect to the working electrode (WE) position are analyzed. For NP-μFEC, the position of the RE with respect to the WE does not affect the CV, DPV electrochemical profiles. However, the spacing between the CE and WE plays a significant role. (iii) The enhanced three-dimensional electric field penetration in NP-μFEC is validated by finite element analysis simulation using COMSOL Multiphysics. (iv) Without electrode surface modifications, NP-μFEC shows a detection limit (DL) of ∼2.54 × 10−6 M for aqueous [Fe(CN)6]3-/4- probe. (v) The DL for Cu2+, Fe3+, and Hg2+ are 30.5±9.5 μg L−1, 181±58.5 μg L−1, and 12.4±1.95 μg L−1, respectively, which meets the US Environmental Protection Agency (EPA)'s water contamination level for Cu, Fe, and is close to that for Hg (EPA limits are 1300 μg L−1, 300 μg L−1, and 2 μg L−1, respectively). (vi) Further, using a pressure-sensitive adhesive layer to form the channel and create the NP-μFEC configuration simplifies the manufacturing process, making it cost-effective and allowing for rapid adoption in any research lab. NP-μFEC is used to detect heavy metal ions in water. This demonstrates that cost-effective, easy-to-fabricate NP-μFEC can be a new sensitive electrochemical platform.