Device architecture of the microfluidic electrochemical array and microfabrication process flow. The modular architecture allows independent processing of (a) the electrode substrate and (b) the chamber substrate, which are then fusion bonded to form a monolithic device. (c) Integrated PDMS microvalves enable precise fluidic metering of analyte solutions into the 750 nL detection chamber. (d) Optical micrograph of the device illustrating the gold sensor electrodes (S1, S2, and S3), platinum reference electrode (R), and counter electrode (C). The sensor electrodes are 900 μm × 900 μm in size, and the center-to-center pitch between S1 and S2 is 2 mm.