Portable Atmospheric\nAir Plasma Jet Pen for the Surface\nTreatment of Three-Dimensionally (3D)-Printed Electrodes

Three-dimensional (3D) printing is an emerging technology\nto develop\ndevices on a large scale with potential application for electroanalysis.\nHowever, 3D-printed electrodes, in their native form, provide poor\nelectrochemical response due to the presence of a high percentage\nof thermoplastic polymer in the conductive filaments. Therefore, surface\ntreatments are usually required to remove the nonconductive material\nfrom the 3D-printed electrode surfaces, providing a dramatic improvement\nin the electroanalytical performance. However, these procedures are\ntime-consuming, require bulky equipment, or even involve non-eco-friendly\nprotocols. Herein, we demonstrated that portable and low-cost atmospheric\nair plasma jet pens can be used to activate electrodes additively\nmanufactured using a commercial poly(lactic acid) filament containing\ncarbon black as conductive filler, improving the electrochemical activity.\nRemarkable electrochemical results were obtained (voltammetric profile)\nusing [Fe(CN)<sub>6</sub>]<sup>3–/4–</sup>, dopamine\nand [Ru(NH<sub>3</sub>)<sub>6</sub>]<sup>2+/3+</sup> as redox probes.\nMicroscopic, spectroscopic, and electrochemical techniques revealed\nthat the air-plasma jet pen removes the excess PLA on the 3D-printed\nelectrode surface, exposing the conductive carbon black particles\nand increasing the surface area. The performance of the treated electrode\nwas evaluated by the quantification of capsaicin in pepper sauce samples,\nwith a limit of detection of 3 nM, suitable for analysis of food samples.\nRecovery values from 94% to 101% were obtained for the analysis of\nspiked samples. The new treatment generated by a plasma jet pen is\nan alternative approach to improve the electrochemical activity of\n3D-printed electrodes that present sluggish kinetics with great advantages\nover previous protocols, including low-cost, short time of treatment\n(2 min), environmentally friendly protocol (reagentless), and portability\n(hand-held pen).