The application of coffee-ring effect in analytical chemistry

Coffee-ring effect is an omnipresent phenomenon, it features the circular deposition on the surface after the evaporation of a droplet containing particles. Ever since the seminal report of coffee-ring effect in 1997 from Deegan (Nature 1997, 389 (6653), 827–829), coffee-ring effect related studies have been thriving in various fields. Coffee-ring effect is a spontaneous phenomenon, the capillary flow from the center to the edge of droplet pushes all solute towards the droplet's edge. Therefore, any process involving small droplets especially in the analytical chemistry has to deal with coffee-ring effect. This review aims to offer an in-depth understanding of coffee-ring effect in analytical chemistry, includes the formation mechanism, controlling factors, as well as categorized applications based on the essence of factors. Lastly, the limitation and the future trends of this technique in analytical chemistry are discussed, offering our insights on the development of this technique and aiming to promote the application of this technique.