This paper presents a study on the formation of ring-like deposits in evaporating drops. The phenomenon occurs when solids are dispersed in a drying drop and migrate to the edge, forming a ring. The researchers show that this migration is caused by an outward flow within the drop, driven by evaporation and the geometric constraint that the drop maintains an equilibrium shape. They develop a theory that predicts the flow velocity, the rate of growth of the ring, and the distribution of solute within the drop. The theory is validated against experimental results. The study shows that the migration of solute to the edge of the drop is due to an outward flow of liquid, which is driven by evaporation and the need to maintain the drop's shape. This flow can transfer 100% of the solute to the contact line, resulting in the strong perimeter concentration of many stains. The theory relies on the presence of surface roughness or chemical heterogeneities that produce contact line pinning, which is a common feature of many surfaces. The researchers conducted a series of experiments using various carrier fluids, solutes, and substrates, and found that the preferential deposition at the contact line is insensitive to a wide range of experimental conditions. They observed ring-like deposits on a variety of surfaces, including glass, metal, polyethylene, and silicon, with solutes ranging in size from molecular to colloidal. The results showed that the evaporation rate is diffusion-limited, and the deposition is primarily due to the outward flow of liquid. The theory was tested against experimental results, and the predictions were found to be in agreement with the experiments. However, there were some discrepancies that suggest the importance of other mechanisms. The researchers also demonstrated that the ring growth initially follows a power law in time and then rapidly increases and diverges. The theory predicts that the solute is completely transferred to the edge of the drop, which is supported by the experimental results. The study concludes that the theory provides a useful tool for understanding and predicting the ring-formation process. It accounts for the widespread occurrence of solute rings, as few ingredients are required—a weakly pinning substrate and evaporation—and these ingredients occur commonly. The theory also indicates how manipulating the vapor field around the drop provides a means of controlling the deposition process. The potential for controlling deposition on a surface using this contact line deposition remains virtually unexplored, and the study suggests that further research is needed to explore this potential.This paper presents a study on the formation of ring-like deposits in evaporating drops. The phenomenon occurs when solids are dispersed in a drying drop and migrate to the edge, forming a ring. The researchers show that this migration is caused by an outward flow within the drop, driven by evaporation and the geometric constraint that the drop maintains an equilibrium shape. They develop a theory that predicts the flow velocity, the rate of growth of the ring, and the distribution of solute within the drop. The theory is validated against experimental results. The study shows that the migration of solute to the edge of the drop is due to an outward flow of liquid, which is driven by evaporation and the need to maintain the drop's shape. This flow can transfer 100% of the solute to the contact line, resulting in the strong perimeter concentration of many stains. The theory relies on the presence of surface roughness or chemical heterogeneities that produce contact line pinning, which is a common feature of many surfaces. The researchers conducted a series of experiments using various carrier fluids, solutes, and substrates, and found that the preferential deposition at the contact line is insensitive to a wide range of experimental conditions. They observed ring-like deposits on a variety of surfaces, including glass, metal, polyethylene, and silicon, with solutes ranging in size from molecular to colloidal. The results showed that the evaporation rate is diffusion-limited, and the deposition is primarily due to the outward flow of liquid. The theory was tested against experimental results, and the predictions were found to be in agreement with the experiments. However, there were some discrepancies that suggest the importance of other mechanisms. The researchers also demonstrated that the ring growth initially follows a power law in time and then rapidly increases and diverges. The theory predicts that the solute is completely transferred to the edge of the drop, which is supported by the experimental results. The study concludes that the theory provides a useful tool for understanding and predicting the ring-formation process. It accounts for the widespread occurrence of solute rings, as few ingredients are required—a weakly pinning substrate and evaporation—and these ingredients occur commonly. The theory also indicates how manipulating the vapor field around the drop provides a means of controlling the deposition process. The potential for controlling deposition on a surface using this contact line deposition remains virtually unexplored, and the study suggests that further research is needed to explore this potential.