Self-powered sensors driven by osmotic energy: From fundamentals to applications

With the rapid development of nanofluidic materials and the urgent demand for low-power self-sustaining sensing systems, developing osmotic energy-driven self-powered sensors has become a research focus. Osmotic energy, a promising blue energy with enormous reserves, has long been underutilized due to the limitations of traditional harvesting technologies. In contrast, integrated self-powered sensing driven by osmotic energy achieves seamless integration of energy conversion and sensing via advanced nanofluidic membranes and selective ion transport, exhibiting superior miniaturization and efficient signal transduction. However, previous research focuses on separated design of such systems; a systematic review focusing on the integrated design of osmotic energy-driven self-powered sensing remains lacking. Herein, we first summarize its fundamentals, including the osmotic energy conversion mechanism, advanced nanomaterials for ion-selective membranes, as well as their selection criteria. Next, typical sensing applications in nutrient, pressure, humidity, and image sensing are discussed, with emphasis on the specific sensing mechanisms underlying each category, such as light-regulated surface charge density for image sensing. Additionally, other emerging applications like self-powered lithium extraction and hydrogen production are presented. Finally, critical challenges and future research directions are proposed, aiming to guide the practical development and large-scale integration of such sensing systems.