3D-Printed Templates Converted into Graphite, Ruthenium, or Copper Are Used as Monolithic Sensors

Sensors based on 3D-printed pieces made with conductive filaments are promising to decrease the cost and time of analysis. However, the conductivity of these sensors is lower than that necessary for electrochemical detection, requiring postprinting treatment. Considering that the post-treatment is mandatory to date, we used an electrochemical surface modification to convert an insulating plastic into a conductive material, eliminating the need for using a conductive filament. We used cyclic voltammetry to grow polyaniline on a polylactic acid surface in the presence of graphite (GR) in the form of trails. This simple step built a monolithic 3D-printed sensor integrated with a GR working electrode (WE). Such a sensor coupled to a minipotentiostat was used to detect caffeine by chronoamperometry in an aqueous solution with a limit of detection of 57.7 μmol L–1. We also electrodeposited Ru and Cu on the WEs, which were used for H2O2 and glucose sensing with the detection limited to 2.3 and 49.3 μmol L–1, respectively. This technique can be applied to any existing plastic object to manufacture integrated (all-in-one), stable, low-cost, and disposable sensors.