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Patterning of Small Particles & Surface Tension vs. Temperature

Patterning of Small Particles & Surface Tension vs. Temperature. Lu Zou Group meeting Jul. 10, ’06 Ref: Nguyen, V.X.; Stebe, K. J.; PRL, Vol. 88, 16, 164501, 2002. Patterning of Nanoparticles. A drop containing finely divided particles Evaporation

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Patterning of Small Particles & Surface Tension vs. Temperature

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  1. Patterning of Small Particles&Surface Tension vs. Temperature Lu Zou Group meeting Jul. 10, ’06 Ref: Nguyen, V.X.; Stebe, K. J.; PRL, Vol. 88, 16, 164501, 2002

  2. Patterning of Nanoparticles • A drop containing finely divided particles • Evaporation • Particles are deposited in macroscopic patterns • Interactions among the particles can be exploited to create local order

  3. R. D. Deegan and others 1997. "Capillary flow as the cause of ring stains from dried liquid drops", Nature, volume 389, pp827-829 M. Maillard, L. Motte, M.-P. Pileni ; Rings and Hexagons Made of Nanocrystals, Adv. Mater. 2001, 13, 200-204 (or say, periodic flow patterns, Hexagon patterns) “Coffee Ring” & “Benard Cells”

  4. Why a drying drop forms a “Coffee Ring”? Ref:http://mrsec.uchicago.edu/ Nuggets/Coffee/

  5. Benard Convection physics.ucsd.edu/was-daedalus/ convection/rb.html

  6. A Droplet with Surfactant Pentadecanoic Acid (PDA) Dyed by NBD-HDA HCl + 0.01% microspheres (D = 0.8um) Modified SiO2 Substrate Contact angle for water is 50o +/- 3o

  7. Isotherm of PDA w/ NBD-HDA

  8. For the LC-LE State

  9. For the LE State When the interface is in LC-LE coexistence, the Benard convection is present, even though the concentration of the surfactant is significant.

  10. 2 Possible Explanation • In the LE-LC coexistence regime, compositional Marangoni stresses are weak. • In the LE-LC coexistence regime, temperature-driven Marangoni stresses are strong.

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