Swollen hydrogel nanotechnology: Advanced applications of the rudimentary swelling properties of hydrogels

Hydrogels, which are three-dimensional networks of crosslinked hydrophilic polymers, have become crucial for various advanced applications owing to their exceptional water absorption and swelling properties. This review explores the applications of hydrogels based on their unique swelling properties, beyond their application in traditional drug delivery, focusing on atmospheric water harvesting, hydrogel actuator, expansion microscopy (ExM), and 3D nanofabrication through controlled deswelling. We first discuss the factors influencing hydrogel swelling, such as network size and polymer properties. Next, we explore the mechanisms underlying hydrogel swelling, emphasizing the interplay between various forces. Hydrogel swelling enables ExM for super-resolution imaging of biological tissues, while controlled deswelling of hydrogels facilitates the creation of intricate 3D structures with nanoscale precision—a breakthrough for additive manufacturing techniques. Despite these advantages, challenges still remain. We conclude this review by emphasizing the need for interdisciplinary research to address these limitations and unlock the full potential of the hydrogel technology. The future of hydrogel research holds promise for revolutionary contributions to environmental science, robotics, and biomedical imaging.