A Low-Cost, Scalable ENIG-PCB Electrode Platform With Reproducible Performance for Electrochemical Biosensing

Abstract

Electrochemical biosensors are widely used in clinical diagnostics, but commercial substrates that meet reproducibility requirements cost several U.S. dollars per electrode, placing both point-of-care deployment and high-throughput biosensor research out of reach. Printed circuit board (PCB) electrodes with an electroless nickel/immersion gold (ENIG) finish offer the same surface metal at a fraction of the cost but suffer from electrode-to-electrode variability driven by the thin commercial gold finish. We report a two-step cleaning and conditioning protocol that brings independently prepared ENIG-PCB electrodes to a single, reproducible electrochemical baseline. Multimodality surface characterization (X-ray photoelectron and scanning electron microscopy (SEM), contact angle, and stylus profilometry) confirms removal of the contaminant overlayer and reduction of nickel-oxide character. Across an independently prepared cohort of N = 49 cleaned electrodes, the charge-transfer resistance averages 45.43 plus-minus 2.67 Omega with a coefficient of variation of 5.88 percnet. Across a 20-fold concentration range of the ferri-/ferrocyanide redox probe, the cleaned platform reproduces the diffusion-controlled Randles-Sevcik scaling (Ipa is proportional to C sup(1.01), R sup(2) = 0.999) and peak symmetry (|Ipa/Ipc| =1.03 plus-minus 0.02 and N = 12) characteristic of standard polycrystalline-gold electrodes. As a proof of concept, a sandwich-format Beta -hCG (Beta -human chorionic gonadotropin) immunoassay on the cleaned platform yields a signal-to-noise ratio of 30 relative to the blank. The per-electrode substrate cost is approximately 6.8 (<| 10), enabling both clinical deployment and biosensor method development on a commercially scalable substrate.