The base of the electrochemical cell with dimensions of 50 mm × 50 mm × 12 mm was built from UV curable resin using a Phrozen Sonic Mini 8K printer. A silica microscope slide of thickness 0.5 µm was embedded into the base for direct visualization of the concentration field via fluorescence microscopy. Flow fields cast from PDMS housed the electrodes. The fluorescent half-cell consisted of a print-and-plate electrode on a 13 mm x 3 mm rectangular flow field designed to snugly fit the electrode inside. The non-fluorescent halfcell has a 2 cm x 1 cm serpentine flow field that can be used with various chemistries.