A poly(methyl methacrylate) (PMMA) microfluidic platform with a hot-embossed microchannel, 150 mm wide by 20 mm deep, was developed for multiple purpose electrochemical detection and mechanistic studies. The platform was tested using a redox couple consisting of Fe(CN)₆⁻³ and Fe(CN)₆⁻⁴ with 100 mM KCl supporting electrolyte. The device includes microelectrodes installed in the microchannel. It accommodates a three-electrode system, with each electrode encased in 1/16” diameter PEEK tubing. These electrodes are removable so they can be re-used after cleaning, polishing and can be calibrated before and after experimental runs. The working microelectrode is a micro-disc made of platinum, and a platinum wire is the counter electrode. Other types of working and counter electrodes can be used and their surfaces can be modified depending on the target analyte under consideration. A commercial, true "leak-less" reference electrode was employed, which is stable, durable and which avoids cross-contamination.

Characterization of the microchip was performed using electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry. Hydrodynamic tests were performed at flow rates between 0.1 and 10 mL/min, and analyte concentrations between 5 and 20 mM. The effect of scan rates in the range 20-100 mV/s during cyclic voltammetry was also studied. It was found that application of convection greatly enhances the current density at the micro electrode surface. At sufficiently high flow rates the voltammetric response exhibits the expected steady-state curve, at any of the studied scan rates. The limiting current increased in direct proportion to the concentration, and a cube root proportionality between limiting current and average fluid velocity was found. This is in agreement with 3D numerical modeling done in COMSOL Multiphysics® v5.3, using Butler-Volmer electrode kinetics, the Nernst-Planck equations for ion transport and Navier-Stokes equations for the hydrodynamic flow. Our model is used to simulate cyclic voltammetry and chronoamperometry at different flow rates, concentrations, and scan rates as well as for data regression and parameter estimation.