Surfactant-driven flow transitions in evaporating droplets
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This work is able to show that different types of surfactants turn the droplet's surface either rigid or elastic, which alters the evaporating fluid flow, either enhancing the classical coffee-stain effect or leading to a total flow inversion.Abstract:
An evaporating droplet is a dynamic system in which flow is spontaneously generated to minimize the surface energy, dragging particles to the borders and ultimately resulting in the so-called "coffee-stain effect". The situation becomes more complex at the droplet's surface, where surface tension gradients of different nature can compete with each other yielding different scenarios. With careful experiments and with the aid of 3D particle tracking techniques, we are able to show that different types of surfactants turn the droplet's surface either rigid or elastic, which alters the evaporating fluid flow, either enhancing the classical coffee-stain effect or leading to a total flow inversion. Our measurements lead to unprecedented and detailed measurements of the surface tension difference along an evaporating droplet's surface with good temporal and spatial resolution.read more
Citations
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A review on suppression and utilization of the coffee-ring effect.
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References
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Book
CRC Handbook of Chemistry and Physics
TL;DR: CRC handbook of chemistry and physics, CRC Handbook of Chemistry and Physics, CRC handbook as discussed by the authors, CRC Handbook for Chemistry and Physiology, CRC Handbook for Physics,
Journal ArticleDOI
Capillary flow as the cause of ring stains from dried liquid drops
TL;DR: In this article, the authors ascribe the characteristic pattern of the deposition to a form of capillary flow in which pinning of the contact line of the drying drop ensures that liquid evaporating from the edge is replenished by liquid from the interior.
Journal ArticleDOI
Contact line deposits in an evaporating drop
TL;DR: A theory is described that predicts the flow velocity, the rate of growth of the ring, and the distribution of solute within the drop that is driven by the loss of solvent by evaporation and the geometrical constraint that the drop maintain an equilibrium droplet shape with a fixed boundary.
Journal ArticleDOI
Marangoni effect reverses coffee-ring depositions.
Hua Hu,Ronald G. Larson +1 more
TL;DR: It is shown here both experimentally and theoretically that the formation of "coffee-ring" deposits observed at the edge of drying water droplets requires not only a pinned contact line but also suppression of Marangoni flow.
Journal ArticleDOI
Pattern formation in drying drops
TL;DR: The drop itself can generate one of the essential conditions for ring formation to occur: contact line pinning, and it is shown that when self-induced pinning is the only source of pinning an array of patterns-that include cellular and lamellar structures, sawtooth patterns, and Sierpinski gaskets-arises from the competition between dewetting and contact linePinning.