Polylactic acid-based prototypes garner the most attention among sustainable substrates, but biopolymers must satisfy various industry and user requirements. Diverse testing conditions and iterative development are also central to our research, and the Horizon Pathfinder EIC project has greatly enhanced our capabilities. Humidity and moisture are factors whose effects on reliable performance must be considered, so in our laboratory experiments, we monitored the moisture absorption of both copper-coated and uncoated polylactic acid samples. Through extended water absorption and drying, we characterized the sustainable substrates, revealing new directions for further development.