However, in this study, the in situ fabrication of the AuNP strip allowed for the accumulation of copper ions and detection in a standard solution down to 3 ppb, linearly up to 400 ppb. The platform was also successfully used to detect copper ions in untreated sweat samples with recovery studies indicating high accuracy. The use of filter paper as a comprehensive tool for the realization of a novel analytical device is particularly noteworthy in the context of sustainable development and autonomous monitoring for nonspecialists. Paper, and in particular filter paper, represents a versatile and costeffective alternative to the more expensive and less sustainable approaches. This approach ensures user-friendly implementation and is a valuable contribution to the development of sustainable analytical tools.