Learning from "coffee rings": Ordered structures enabled by controlled evaporative self-assembly

Research into the evaporation of solutions is not only aimed at a better understanding the physics of evaporation, but increasingly at capitalizing on the extremely simple method it offers to assemble diverse nonvolatile solutes into complex ordered structures on the submicron and longer length scales. This Review highlights recent advances in evaporative assembly of confined solutions, focusing especially on recently developed approaches that provide structures with unprecedented regularity composed of polymers, nanoparticles, and biomaterials, by controlled evaporation-driven, flow-aided self-assembly. A broad range of variables that can control the deposition are explored and the future directions of this rich field are presented. Drying out: The evaporation of solutions of nonvolatile solutes is one way to generate complex ordered structures. An array of facile and robust preparative strategies based on controlled evaporative self-assembly (CESA) of confined solutions have been exploited to rationally assemble various soft and hard materials into spatially ordered structures (see picture) with engineered properties and functionality over large surface areas.