The Math Behind Growth of 'Coffee Rings' (video) University of Pennsylvania Loading video... Caption Last year, a team of University of Pennsylvania physicists showed how to undo the "coffee-ring effect," a commonplace occurrence when drops of liquid with suspended particles dry, leaving a ring-shaped stain at the drop's edges. Now the team is exploring how those particles stack up as they reach the drop's edge, and they discovered that different particles make smoother or rougher deposition profiles at the drop edge depending on their shape. These resultant growth profiles offer tests of deep mathematical ideas about growing interfaces and are potentially relevant for many commercial and industrial coating applications. The video demonstrates the difference between the three types of growth processes the researchers observed in the drying drops. Credit Peter Yunker et. al., University of Pennsylvania Usage Restrictions Must retain credit information on at beginning and end of video. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.