Dynamic and Direct Visualization of the Nanostructure and Functions of Microgels via High‐speed Atomic Force Microscopy

Microgels exhibit fascinating properties and potential for a wide range of applications; however, elucidating the relationships between their structure, properties, and functions remains a major challenge. One of the reasons is the difficulty in visualizing the dynamics of a single microgel swollen by water. In contrast with bulk hydrogels, microgels exist at the submicron scale and cannot be directly observed with the naked eye; therefore, microscopy is essential for the visualization of microgels. Among the many microscopy techniques, we employed high-speed atomic force microscopy (HS-AFM) to evaluate microgels. This technique allows capturing the dynamic behavior of microgels with subsecond-scale temporal resolution and nanometer-scale spatial resolution. In this chapter, recent studies regarding the elucidation of the nanostructure and dynamic behavior of microgels using HS-AFM are overviewed.