IFSpray Coater: Development and Validation of a Low-Cost Open-Source Spray Coating Platform for Gas Diffusion Electrode Fabrication Using a Repurposed 3D Printer

Automation has become increasingly important in laboratory environments, enhancing reproducibility, precision, and efficiency while reducing operator-dependent variability. In materials processing, where small deviations in experimental parameters can strongly affect final properties, automated systems enable tighter control and systematic exploration of process variables. This is particularly relevant for the fabrication of functional electrochemical materials such as gas diffusion electrodes (GDEs), where coating uniformity and thickness directly influence performance in CO₂ electrochemical reduction (CO₂ER) systems. Low-cost and open-source approaches based on repurposed equipment therefore provide accessible alternatives for expanding experimental capabilities in research laboratories. This work aims to develop and experimentally validate a low-cost spray coater, named IFSpray Coater, based on a 3D printer platform for thin-film deposition in GDE fabrication. The system was built from a modified Ender-3 Pro architecture, combining planar motion with a fixed pneumatic spray unit. Trajectory generation was performed using the open-source software 2D SprayPath (PauloFalsetti/2D_SprayPath), enabling parameterized control of x–y scanning patterns. Nozzle height, safety distance, and bed configuration were optimized to ensure stable spray formation and reproducible coatings. A zig-zag scanning strategy was employed, with defined scan area, step size, velocity, and number of repetitions. System performance was assessed by comparing nominal and measured deposition parameters. Results showed strong agreement, with relative errors below 1% for most spatial variables. Scan area deviations remained below 1%, while step size showed slightly higher variation (up to 1.5%) due to mechanical tolerances and motion resolution limits. Spray width remained stable at 3.2 ± 0.5 mm. Two configurations were evaluated (100 × 100 mm² and 60 × 60 mm²), with the latter improving overlap and coating homogeneity. Experimental patterns closely matched simulated trajectories, confirming reliable translation from design to deposition. Overall, the system demonstrated high accuracy and repeatability, supporting low-cost fabrication of GDEs for CO₂ electroreduction systems.