3D-printed electrochemical sensors: from the influence of printing parameters to the improvement of conductive filaments

Abstract

Three-dimensional (3D) printing is an additive manufacturing technique, which makes it possible to obtain a great variety of structures with varied geometries and great versatility. The possibility of obtaining complex objects at a relatively low cost using a wide range of materials provided great attractiveness to 3D printing in areas such as electroanalysis. This technology makes it possible to obtain complete analytical apparatus, such as electrochemical cells and devices, as well as sensors from the use of non-conductive and conductive (composites) filaments. In this context, the objective in this work was to explore commercial conductive filaments based on graphene and polylactic acid (G/PLA) as a base material for obtaining improved sensors for the detection of glucose and H2O2. Glucose detection was performed by incorporating Ni(OH)2 into the printing filament, attributing electrocatalytic properties to the obtained sensor. The new material was characterized by microscopic and spectroscopic techniques, in addition to electrochemical techniques. Subsequently, the sensor produced from this filament was used for the non-enzymatic glucose detection, showing a detection limit of 2.4 µmol L-1, providing fast (160 injections h-1), precise (RSD < 5%) and selective detection of the analyte in the presence of potential interferents such as ascorbic acid, urea and uric acid. For the detection of H2O2, the exposure of iron impurities present in the filament (G/PLA) was performed with a chemical treatment with dimethylformamide for 30 minutes. The Fe3+ ions on the electrode surface were then exploited for the electrodeposition of Prussian blue, which was performed using the cyclic voltammetry technique (200 cycles) in the presence of K3[Fe(CN)6], KCl and HCl. The modified electrode was then used in the amperometric detection of H2O2 using a batch injection analysis (BIA) system. A detection limit of 0.56 μmol L-1 was obtained, in addition to adequate recovery values (94 to 101%) for H2O2 in milk samples. Finally, considering the importance of printing parameters in the final performance of sensors obtained by 3D printing, some parameters such as printing orientation, layer thickness, perimeter number and printing speed were evaluated in sensors obtained from filaments containing carbon black and polylactic acid (CB/PLA). To evaluate the effects of these parameters, characterizations by electrochemical techniques were performed using a solution of 10 mmol L-1 [Ru(NH3)6]2+/3+ as redox probe. Results showed that the electrodes printed in vertical orientation, with lower layer thickness (0.05 mm) and print speed (30 mm s-1) using two perimeter numbers provided the best electrochemical performance. In addition, it was observed that from the selected parameters, there was a greater availability and distribution of conducting sites, showing that the printing parameters are important resources to allow the fabrication of improved electrochemical platforms.