Gel---Soft & Wet Matter with Spatiotemporal Functions

Gel is a two-component, inhomogeneous system consisting of 3D polymer network and fluid. Due to the strong and multiple local interactions between the network and the fluid, gel is inherently dynamic system undergoing continuous and vigorous thermal vibrations with a wide range of frequencies. Gel exhibits a variety of behaviors which bridge solid and liquid states depending on temporal and spatial scales. Owing to their inhomogeneity, gel is able to exhibit discrete and coherent phenomena called emergence with stimuli-responsive functions. This article overviews and discusses the recent progress of gel science emphasizing nonlinear phenomena— emergence— aiming to inspire readers to engage future challenges in gel science.