Prusa i3 mk3 printer

Pendulum-like 3D-printed electrodes were fabricated by fused deposition modeling (FDM) using a Prusa i3 MK3 printer (Prusa Research, Czech Republic). A commercially available Black Magic 3D filament (New York, USA) was used as the raw material, which is made of a conducting graphene-based nanocomposite filler dispersed throughout an insulating PLA polymeric matrix (G/PLA). For the printing, the raw G/PLA filament was extruded down through the nozzle (Olsson Ruby-tipped 0.4 mm, 3DVerkstan, Sweden). The nozzle and the bed temperatures were 215 °C and 60 °C, respectively. For electrochemical measurements, the geometric area employed was 0.28 cm², which corresponds to the one-face spherical part of the pendulum-like 3D-printed G/PLA electrodes exposed in the electrochemical cell, while the linear part was utilized for the electrical contact (see Scheme 1a for illustration). Since the as-printed G/PLA electrodes possess poor conductivity, they were activated by following the standard procedure [39] (link). In brief, as-printed G/PLA electrodes were immersed in DMF for 3 h —in order to partially remove the insulating PLA polymer—, and then electrochemically (EC) activated (bias potential: 2.5 V vs. Ag/AgCl, activation time: 300 s; electrolyte: PBS pH 7.2) to promote the formation of oxygenated groups on the carbon walls exposed on the 3D-printed G/PLA electrode surface.