Jiabei Luo, Antoine Remy, Yujia Zhang
Inspired by the ion transport mechanisms in biological systems, ionic technologies have emerged as a transformative field that bridges biology and electronics. Unlike electrons, ions not only transmit electrical signals but also convey chemical information and exhibit ion-specific transport behaviors. At the center of iontronic devices lie ion channels, highly selective and efficient structures that control ion transport. These ion channels, whether biological nanopores or artificial nanofluidic channels, fundamentally determine the properties of the devices. Therefore, understanding, engineering, and integrating versatile ion channels into artificial systems are critical to advancing the field. This Review provides a comprehensive overview of iontronic devices and systems, mainly covering advances after 2010, beginning with the principles of ion transport in both biological and artificial ion channels. We then examine fabrications and characterizations, with a focus on how material and structural design influence ionic properties. Device architectures are summarized and compared across multiple dimensions and scales. We highlight emerging applications in bioiontronics, neuromorphic computing, energy harvesting, water treatments, and environmental sustainability. Despite significant advancements, we propose that challenges remain in achieving the desired ion selectivity, efficient ionic signal transduction, and seamless integration of iontronics with electronics and biology.