Coherent light and x-ray scattering studies of the dynamics of colloids in confinement

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

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

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

7. Confined fluid under shear stress

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

11. X-ray waveguide

12. X-ray waveguide Silica disk Silica disk visible light : n > 1 hard x rays : n < 1 n =1- δ δ ~10-6 Advantage: large sigal-to-noise ratio

13. Waveguides modes

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

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

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 • Confined complex fluids • Blood • Colloidal and granular (dry) lubricants

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

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. DYNAMIC LIGHT SCATTERING (BULK)

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

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

27. Caging of colloidal particles

28. DYNAMIC X-RAY SCATTERING STUDIES OF CONFINED COLLOIDS

29. Confinement-induced friction?

30. Waveguide dynamic x-ray scattering Top view Side view Silica spheres r =115 nm dissolved in water/Glycerol. Volume fraction 7% (‘dilute’). Negligible particle-particle interaction

31. Short-time confined dynamics W3 = 1.2 micron W4 = 0.8 micron Silica spheres r =115 nm In water /Glycerol

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

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

34. Inhomogeneous particle-wall interactions

35. Investigate inhomogeneous particle-wall interactions

36. Outlook Confined fluids • Smaller waveguide gaps (10 nm) • 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

37. 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.

38. 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