Coherent light and x-ray scattering studies of the dynamics of colloids in confinement Jeroen Bongaerts Thesis defense 16 April 2003, hrs
COHERENT LIGHT AND X-RAY SCATTERING STUDIES OF THE DYNAMICS OF COLLOIDS IN CONFINEMENT University of Amsterdam, Van der Waals-Zeeman Institute Jeroen Bongaerts Dr. Michel Zwanenburg J.F. Peters Dr. Gerard Wegdam ETH-Zürich/PSI-SLS, Switzerland Prof. Dr. Friso van der Veen Dr. Thomas Lackner Heilke Keymeulen
Why study confined fluids? How to study them? Technical improvements Bulk colloidal dynamics Confined colloidal dynamics OUTLINE TALK
WHY STUDY CONFINED FLUIDS?
Examples confined fluids Lubricants Blood in narrow vessels Glue Liquids in porous materials Emulsions used for cold steel rolling Lubricants Blood in narrow vessels Glue Liquids in porous materials Emulsions used for cold steel rolling
From: ‘Intermolecular & Surface Forces’ by Jacob Israelachvili
Confined fluid under shear stress
HOW TO STUDY ULTRATHIN CONFINED FLUIDS? Visible light? No X rays? Yes
X-ray waveguide
visible light : n > 1 hard x rays : n < 1 n =1- δ δ ~10 -6 visible light : n > 1 hard x rays : n < 1 n =1- δ δ ~10 -6 Silica disk X-ray waveguide Silica disk Advantage: large sigal-to-noise ratio
Waveguides modes
x 10 Typical waveguide dimensions 500 nm x 5 mm
Empty waveguide W = 650 nm Experiment Calculation PRL 82 (1999)
Filled x-ray waveguide
CONFINED COLLOIDS (STATIC) Charged colloidal silica spheres r = 54.9 nm, r = 115 nm Solvents: water, water/glucerol, ethanol, DMF Charged colloidal silica spheres r = 54.9 nm, r = 115 nm Solvents: water, water/glucerol, ethanol, DMF Confined complex fluids Blood Colloidal and granular (dry) lubricants Confined complex fluids Blood Colloidal and granular (dry) lubricants
W = 655 nmW = 310 nm Layering of confined colloids (r = 54.9 nm) PRL 85 (2000)
TECHNICAL IMPROVEMENTS 1. Smaller x-ray waveguide gap widths 2. Coherent flux enhancement within the guiding layer
Multi-step-index waveguide geometry Minimum gap: 20 nm (was ca 250 nm)
Enhancing the flux
experimentcalculation No lens With lens
No lens With lens
DYNAMIC LIGHT SCATTERING (BULK)
Dynamic light scattering The dynamic structure factor Speckle Courtesy of J.F. Peters, UvA
Short-time and long-time dynamics (BULK) Dilute bulk suspension Dense bulk suspension
Caging of colloidal particles
Increasing density Increasing Debeye length
DYNAMIC X-RAY SCATTERING STUDIES OF CONFINED COLLOIDS
Confinement-induced friction?
Waveguide dynamic x-ray scattering Silica spheres r =115 nm dissolved in water/Glycerol. Volume fraction 7% (‘dilute’). Negligible particle-particle interaction Silica spheres r =115 nm dissolved in water/Glycerol. Volume fraction 7% (‘dilute’). Negligible particle-particle interaction Top view Side view
Short-time confined dynamics Silica spheres r =115 nm In water /Glycerol W 3 = 1.2 micron W 4 = 0.8 micron
Long-time confinement-induced slowing- down of dynamics Silica spheres r =115 nm In water /Glycerol
Long-time sub-diffusive behavior Silica spheres r =115 nm In water /Glycerol
Inhomogeneous particle-wall interactions
Investigate inhomogeneous particle-wall interactions Investigate inhomogeneous particle-wall interactions
Outlook Smaller waveguide gaps (10 nm) Confined fluids Prefocused x-ray beam (higher flux) J. Synchrotron Rad. 9, (2002) Study particle-wall interactions Surface force measurements combined with static and dynamic x-ray scattering
Summary Confined fluids studied by use of an x-ray waveguide Waveguide technique works Dynamic x-ray scattering in waveguide geometry Confinement affects short and long-time diffusion.
COHERENT LIGHT AND X-RAY SCATTERING STUDIES OF THE DYNAMICS OF COLLOIDS IN CONFINEMENT University of Amsterdam, Van der Waals-Zeeman Institute Jeroen Bongaerts Dr. Michel Zwanenburg J.F. Peters Dr. Gerard Wegdam ETH-Zürich/PSI-SLS, Switzerland Prof. Dr. Friso van der Veen Dr. Thomas Lackner Heilke Keymeulen
Coherent x rays