Nanoscale-enabled cross-scale chemical sensing for underwater monitoring and beyond

In aquatic environments, such as oceans, lakes, and rivers, molecular-level chemical reactions and the distribution of chemical species are related to global environmental changes through various biogeochemical processes. Understanding this relationship requires addressing cross-scale challenges at two distinct levels: overcoming interfacial physical constraints, such as Debye screening in high-salinity waters, at the sensing level and bridging local microscale measurements with macroscale environmental dynamics at the observational level. In this paper, we describe sensing technologies that can enable cross-scale sensing in aquatic environments. Here, we focus on nanoscale interfacial sensing and molecular recognition technologies, as well as lab-on-a-chip technologies for in situ measurements including power-efficient pumping technologies. Additionally, underwater observation platforms that link the local chemical sensing and global processes are overviewed. Beyond environmental applications, these sensing technologies offer a cross-disciplinary approach that can be extended to analyze biological systems facing similar physicochemical constraints.