From laboratory to community: a perspective on colourimetric membrane sensor technologies for heavy metal monitoring in freshwater

Abstract

Heavy metal (HM) pollution continues to threaten freshwater ecosystems worldwide, disproportionately impacting low-resource communities where routine analytical monitoring is often absent. Despite advances in spectroscopy, electrochemical platforms, and automated sensing networks, regular monitoring of potential pollution events by local agencies remains constrained by high costs, specialised equipment, and the need for trained personnel. As a result, contamination events are frequently detected late—after ecological or public health damage has already occurred. Colourimetric sensing offers a complementary pathway toward decentralised early-warning systems. These sensors translate chemical information into visually interpretable colour changes, enabling rapid, inexpensive screening without laboratory infrastructure. In recent years, the field has seen a rise in bio-based membrane formats—cellulose, biopolymers, protein-derived films, and hybrid natural–synthetic composites—motivated by their sustainability, safety, and tunability. Yet their future impact will depend not only on analytical metrics but also on how well they fit into real-world monitoring ecosystems. This Perspective argues that the next decade of progress should be guided not solely by material innovation and continuously lower detection limits, but by a stronger focus on practical deployability, community integration, and environmental responsibility.