Generation of the smallest coffee-ring structures by solute crystallization reaction on a hydrophobic surface

Abstract

We have successfully produced micro-scale “coffee-rings” by crystallization reaction on a hydrophobic surface. The diameter of the rings is only about 8 μm, which to the best of our knowledge is the smallest of any artificial coffee-ring structures in the world. Furthermore, these new patterns are distributed uniformly over the whole macro-scale substrate, which is meaningful for real applications.