1. Coherent light and x-ray scattering studies of the dynamics of colloids in confinement Jeroen Bongaerts Thesis defense 16 April 2003, 14.00 hrs

2. 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

3. Why study confined fluids? How to study them? Technical improvements Bulk colloidal dynamics Confined colloidal dynamics OUTLINE TALK

4. WHY STUDY CONFINED FLUIDS?

5. 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

6. From: ‘Intermolecular & Surface Forces’ by Jacob Israelachvili

7. Confined fluid under shear stress

8. HOW TO STUDY ULTRATHIN CONFINED FLUIDS? Visible light? No X rays? Yes

11. X-ray waveguide

12. 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

13. Waveguides modes

14. x 10 Typical waveguide dimensions 500 nm x 5 mm

15. Empty waveguide W = 650 nm Experiment Calculation PRL 82 (1999)

16. Filled x-ray waveguide

17. 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

18. W = 655 nmW = 310 nm Layering of confined colloids (r = 54.9 nm) PRL 85 (2000)

19. TECHNICAL IMPROVEMENTS 1. Smaller x-ray waveguide gap widths 2. Coherent flux enhancement within the guiding layer

20. Multi-step-index waveguide geometry Minimum gap: 20 nm (was ca 250 nm)

21. Enhancing the flux

24. experimentcalculation No lens With lens

25. No lens With lens

26. DYNAMIC LIGHT SCATTERING (BULK)

27. Dynamic light scattering The dynamic structure factor Speckle Courtesy of J.F. Peters, UvA

28. Short-time and long-time dynamics (BULK) Dilute bulk suspension Dense bulk suspension

29. Caging of colloidal particles

30. Increasing density Increasing Debeye length

31. DYNAMIC X-RAY SCATTERING STUDIES OF CONFINED COLLOIDS

32. Confinement-induced friction?

33. 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

34. Short-time confined dynamics Silica spheres r =115 nm In water /Glycerol W 3 = 1.2 micron W 4 = 0.8 micron

35. Long-time confinement-induced slowing- down of dynamics Silica spheres r =115 nm In water /Glycerol

36. Long-time sub-diffusive behavior Silica spheres r =115 nm In water /Glycerol

37. Inhomogeneous particle-wall interactions

38. Investigate inhomogeneous particle-wall interactions Investigate inhomogeneous particle-wall interactions

39. Outlook Smaller waveguide gaps (10 nm) Confined fluids Prefocused x-ray beam (higher flux) J. Synchrotron Rad. 9, 383---393 (2002) Study particle-wall interactions Surface force measurements combined with static and dynamic x-ray scattering

40. 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.

41. 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

42. Coherent x rays