Fabrication and Characterization of a Tunable Microelectrode Array Probe for Simultaneous Multiplexed Electrochemical Detection

Individually addressable microelectrode arrays (MEAs) enable the simultaneous and independent measurement of multiple analytes and benefit from a small size scale, which enables highly localized electrochemical detection. In this work, we describe a new methodology to fabricate low-cost and tunable MEA probes in which the number, spatial arrangement, and spacing of the electrodes and electrode material can be changed and controlled. This was achieved using a 3D printed support assembly to position wires of the electrode material into designated positions and a mold to seal the electrodes in place using epoxy resin. After curing of the epoxy, mechanical polishing exposed the surface of closely spaced disk microelectrodes embedded in the insulating material, which formed the MEA. The individual electrodes of the array were characterized using electrochemical methods and optical and electron microscopy to evaluate the surface quality and the integrity of the seal with the insulating epoxy. To validate the fabrication method and to demonstrate the controlled electrode spacing, we used a dual-disk electrode device, while four-, five-, and seven-electrode probes were used to demonstrate some of the different numbers and geometric arrangements of electrodes that are possible. While the developed probes have numerous potential applications, including as probes or substrates in scanning electrochemical microscopy, we fabricated electrochemical aptamer-based sensors on the individual electrodes, for the simultaneous detection of adenosine triphosphate and dopamine in phosphate-buffered saline solution, with and without 10% fetal bovine serum.