Wetting When It Isn

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Wetting When It Isnt Simple!P.S. Pershan,
Harvard Univ.
Simple Wetting
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Three Different Experiments

• 1) Casimir Effect Critical Binary Liquid
• Fisher and de Gennes (1978), Krech and Dietrich
  (1991, 1992)
• Correlation Length

M. Fukuto,Y. Yana
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2) Structured SurfaceC. Rascon and A. O. Parry,
Nature 407, 986 (2000).
O. Gang, B.Ocko,, K.Alvine, T. Russell,M. Fukuto,
C. Black
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3) Reconstructing Surface
D. Pontoni, K. Alvine, A. Checco, O. Gang, B.
Ockio, F. Stellacci
Nanoparticles Controlled Solvation
Thiol Stabilized Au Particles( 2 to 8 nm)
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Control of Film Thickness
Vapor Pressure? Thickness
Delicate Control
????P??? ?T?
Van der Waals
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X-Ray Reflectivity Film Thickness
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Example of 1/3 Power Law
Methyl cyclohexane (MC) on Si at 46 C
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Critical Casimir Effect in NanoThick Liquids
Binary Liquid
Fisher and de Gennes (1978), Krech and Dietrich
(1991, 1992)
Methylcyclohexane (MC)
Perfluoro- methylcyclohexane (PFMC)
Heady Cahn, J. Chem. Phys. 58, 896 (1973) Tc
46.13 ? 0.01 C, xc 0.361 ? 0.002
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Thermodynamics
Same Experiment Thickness of Absorbed Film
Critical Point
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X-ray reflectivity Film thickness D
Paths
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Theory
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Experiment vs. Theory
There is prediction for ????????for 3D.
Theory for y-dependence in d3 does not exist!
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Universal Casimir amplitudes
At bulk Tc (t 0), scaling functions reduce to
D ? q(0) Q(0)/(d 1)
For d 3 Ising systems D, D,-
Renormalization Group (RG) Monte Carlo M. Krech, PRE 1997 -0.326 -0.345 2.39 2.450
Local free energy functional theory (LFEF) Z. Borjan P. J. Upton, PRL 1998 -0.42 3.1
Our Result N/A 3 1
For recent experiments with superfluid He (XY
systems), see R. Garcia M.H.W. Chan, PRL
1999, 2002 T. Ueno et al., PRL 2003
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Sculpted Surfaces
Theory Rascon Parry, Nature (2000)
Crossover Geometry to Planar
Planar
Geometry Dominated
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Parabolic Pits Tom Russell (UMA)
Diblock Copolymer in Solvent
40 nm Spacing 20 nm Depth/Diameter
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X-ray Grazing Incidence Diffraction (GID)
In-plane surface structure
Liquid Fills Pore Scattering Decreases
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X-ray Measurement of Filling
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Results for Sculpted Surface
Sculpted is Thinner than Flat
Flat Sample
?c?????
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Tasinkevych Dietrich
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Reconstructing SurfaceGold Nanoparticles
Controlled Solvation
Stellacci et al (MIT) OT MPA (21)OTCH3(CH2)7S
HMPAHOOC(CH2)2SH
Liftoff Area Of Monolayer
Bimodal Size Distribution of Particles
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GID X-ray vs. Liquid Adsorption(small particles)
Return to Dry
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Temperature Dependence of Reflectivity
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Construction of Model Dry Sample
Model Fit Based on Particle Size Distribution
Vertical electron density profile
Core size distribution
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Fits of Physical Model
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Evolution of Model with Adsorption
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Summary of Nano-particle experiments
Bimodal Au nanocrystals in equilibrium with
undersaturated vapor
Poor vs..... Good Solvent
Good Solvent
Aggregation in Poor Solvent
Reversible
Dissolution in Good Solvent
Self Assembly
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Summary

• Delicate Control of Wetting ?????
• Wetting of Critical Liquid (Casimir)
• M. Fukuto,Y. Yana
• Wetting of Structured Surface (Rascon/Parry
  Tasikevych/Dietrich)O. Gang, B.Ocko,, K.Alvine,
  T. Russell,M. Fukuto, C. Black
• Nano-Particles Self Assembly D. Pontoni, K.
  Alvine, A. Checco, O. Gang, B. Ockio, F. Stellacci