Brown University School of Engineering

Fluids Seminar: Impact of Surface-absorbed particles on Interfacial Phenomena: From Landau-Levich Problem to Armored Drops

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Tuesday, October 15, 2013 3:00pm - 4:00pm

Malika Ouriemi Brown University Impact of surface-absorbed particles on interfacial phenomena: from Landau-Levich problem to armored drops We present an experimental study of the impact of surface-absorbed particles on interfacial phenomena, focusing on two particular configurations. 1. Coating of liquids with particles absorbed on the interface Experiments realized with small hydrophobic particles show a thickening effect compared with Newtonian fluids on a smooth substrate and a different power of capillary number than the classical Landau-Levich law. The measured power law is consistent with the recent theory [Dixit and Homsy, 2013] that extends the Landau-Levich law for the case in which the interface possesses both elasticity and surface tension. 2. Electrodynamics of drops with an interface partially or completely covered with microscopic particles A weakly conductive drop immersed in a more conductive liquid first undergoes an oblate deformation, and then experiences a rotation similar to Quincke rotation when submitted to an increasing DC uniform electrical field. We show that adding particles at the drop interface, leads to more complex behaviors. Depending on the field intensity, and the characteristics of the particles, the drop exhibits: (i) prolate deformation, (ii) emergence of pattern of sustained particle motions, or (iii) decrease of the electrical field that induces rotation.