title: Evaporative deposition in receding drops.
abstract: We present a framework for calculating the surface density profile of a stain deposited by a drop with a receding contact line. Unlike a pinned drop, a receding drop pushes fluid towards its interior, continuously deposits mass across its substrate as it evaporates, and does not produce the usual "coffee ring." For a thin, circular drop with a uniform evaporation rate, we find the surface density of the stain goes as η(r) ∝ ((r/a0)(-1/2)-r/a0), where r is the radius from the drop center and a0 is the initial outer radius. Under these conditions, the deposited stain has a mountain-like morphology. Our framework can easily be extended to investigate new stain morphologies left by drying drops.
authors.affiliation: Department of Physics, The James Franck Institute, University of Chicago, 929 E 57th Street, Chicago, IL 60637, USA. jfreedbrown@uchicago.edu.
authors.forename: Julian
authors.initials: J
authors.lastname: Freed-Brown