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Dynamic Photocontrol of the Coffee‐Ring Effect with Optically Tunable Particle Stickiness
Author(s) -
Anyfantakis Manos,
Baigl Damien
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201406903
Subject(s) - drop (telecommunication) , coffee ring effect , particle (ecology) , materials science , particle deposition , on demand , nanoparticle , chemical physics , nanotechnology , homogeneous , colloid , deposition (geology) , particle aggregation , chemical engineering , optics , chemistry , range (aeronautics) , composite material , physics , organic chemistry , telecommunications , paleontology , oceanography , multimedia , engineering , sediment , geology , biology , computer science , thermodynamics
When a colloidal drop dries on a surface, most of the particles accumulate at the drop periphery, yielding a characteristic ring‐shaped pattern. This so‐called coffee‐ring effect (CRE) is observed in any pinned evaporating drop containing non‐volatile solutes. Here, the CRE is dynamically controlled for the first time by using light, and an unprecedented reconfigurability of the deposit profile is demonstrated. This is achieved through a new mechanism where particle stickiness is optically tuned on demand, thus offering reliable modulation of the deposition pattern. The system consists of anionic nanoparticles and photosensitive cationic surfactants dispersed in water. It is shown that light‐dependent modulation of surfactant–particle interactions dictates particle attraction and trapping at the liquid–gas interface, which allows us to direct particle deposition into a wide range of patterns from rings to homogeneous disks. Patterning from single drops is photoreversible upon changing the wavelength whereas spatial control in multiple drop arrays is achieved using a photomask.