Recent Advances in Reactive Microdroplets for Clean Water and Energy.

Microdroplets have emerged as powerful and sustainable platforms for the design and synthesis of functional materials under mild and environmentally friendly conditions. Their unique physicochemical environments - characterized by high surface-to-volume ratios and confined internal space - enable precise control over mass and heat transfer, interfacial energy conversion, and chemical reactions. These features have been harnessed in two main ways: first, by employing microdroplets as microreactors for the fabrication of advanced materials such as polymeric microlenses, artificial compound eyes, metal oxide nanoparticles, and metal-organic framework microstructures; and second, by using microdroplets as reactive entities to accelerate interfacial reactions relevant to hydrogen and biodiesel production, as well as nitrogen and carbon dioxide fixation. Together, these strategies have driven significant advances in clean energy generation, environmental monitoring, and water treatment. This review provides a critical overview of recent progress in microdroplet-assisted synthesis of functional materials and their integration in energy and environmental technologies. An emerging direction in the integration of microdroplet-based systems into adaptive sensing and human-machine interfaces driven by artificial intelligence is also highlighted.