Direct Electrode Modification of Paper-based Microfluidic Sensors through Electrodeposition and Electropolymerization

Commonly employed are screen-printed carbon-based electrodes (SPCE) as a suitable low-cost sensing platform. Microfluidic electrochemical sensors (mu CS) can also be portable, highly sensitive, and low-cost but are less seldom studied and applied. Here we demonstrate the superior performance of mu CS over SPCE arrangements. Additionally, electrodeposition of gold nanoparticles (ED (AuNPs)) and electropolymerization of L-cysteine (EP (Lcys)) are introduced for the first time for modifying the surface of the working electrode through a paper-based microfluidic sensor. The study depicts that by employing such modification the electrochemically active surface area (ECSA) and the electron transfer rate in both arrangements are increased together and result in improved sensitivity. Both arrangements were compared using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in [Fe(CN)6](3-/4-). mu CS offers several advantages over SPCEs in terms of cost, simplicity, and sensitivity, making them a promising platform for point-ofcare diagnostics and environmental monitoring.