Thermoplastic Electrode Arrays in Electrochemical Paper-Based Analytical Devices

Electrochemical paper-based analytical devices (ePADs) have garnered significant interest as an alternative to traditional benchtop methods due to their low cost and simple fabrication. Historically, ePADs have relied almost exclusively on single electrode detection, limiting potential gains in sensitivity and selectivity achievable with multiple electrodes. Herein we describe incorporation of thermoplastic electrode (TPE) arrays into flow ePADs. Quasi-steady flow was solely generated by capillary action through a fan-shaped paper device. The electrode arrays were fabricated using a simple solvent-assisted method with inexpensive materials (i.e., graphite and thermoplastic binder). These electrodes can be employed as an array of individually addressable detectors or connected as an interdigitated electrode array. The TPEs were characterized through SEM, optical profilometry and cyclic voltammetry. Chronoamperometry was used to characterize the flow-based TPE-ePADs. Trace detection of a ferrocene complex (FcTMA⁺) was demonstrated through generation-collection experiments, achieving a limit of detection of 0.32 pmol. These TPE arrays containing ePADs show great promise as a rapid, sensitive, and low-cost sensor for point-of-need (PON) applications.