Have you ever spilled your cup of coffee? You may have noticed how the coffee dries into an intriguing stain with a bright centre and a dark ring encircling it. This “coffee ring” forms because the liquid evaporates faster at the edges, inducing a flow from the droplet interior towards the outside. Suspended solid coffee particles thus accumulate at the drop edge, causing the characteristic ring pattern.
In Nature Communications, we present a simple, yet versatile strategy to overcome the omnipresent coffee ring effect and achieve homogeneous drying patterns of particle dispersions. Our trick is to modify dispersed particles with surface-active polymeric additives. This induces additional steric repulsion, which prevents particle accumulation at the droplet edge and promotes adsorption to the droplet surface, resulting in a homogeneous particle film upon drying. Importantly, the presented method is independent of particle shape and applicable to a variety of commercial pigment particles and different dispersion media.