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Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans PowerPoint Presentation
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Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans

Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans

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Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans

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  1. Drops on patterned surfaces Halim Kusumaatmaja Alexandre Dupuis Julia Yeomans

  2. Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

  3. Equations of motion Navier-Stokes equations continuity Navier-Stokes No-slip boundary conditions on the velocity

  4. Equilibrium free energy bulk term interface free energy surface term Van der Waals controls surface tension controls contact angle

  5. Controlling the contact angle Surface free energy Minimising the free energy leads to: Boundary condition on the Euler-Lagrange equation A relation between the contact angle and the surface field

  6. Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

  7. Chemically striped surfaces: drop spreading

  8. Experiments (J.Léopoldès and D.Bucknall) 64o / 5o

  9. LB simulations on substrate 4 • Two final (meta-)stable state observed depending on the point of impact. • Dynamics of the drop formation traced. • Quantitative agreement with experiment. Simulation vs experiments Evolution of the contact line

  10. Impact near the centre of the lyophobic stripe

  11. Impact near a lyophilic stripe

  12. LB simulations on substrate 4 • Two final (meta-)stable state observed depending on the point of impact. • Dynamics of the drop formation traced. • Quantitative agreement with experiment. Simulation vs experiments Evolution of the contact line

  13. 80o /90o

  14. Two wide stripes: 110o /130o hydrophilic hydrophobic hydrophilic

  15. 80o /90o

  16. Characteristic spreading velocityA. Wagner and A. Briant

  17. Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

  18. Hysteresis

  19. Hysteresis

  20. Hysteresis

  21. Hysteresis

  22. Hysteresis

  23. Hysteresis

  24. Hysteresis

  25. Hysteresis

  26. Hysteresis

  27. Hysteresis slips at angle advancing

  28. Hysteresis pinned until

  29. Hysteresis pinned until

  30. Hysteresis slips smoothly across hydrophobic stripe

  31. Hysteresis slips smoothly across hydrophobic stripe

  32. Hysteresis jumps back to

  33. Hysteresis advancing stick slip jump (slip)

  34. Hysteresis advancing stick slip jump (slip) receding stick (slip) jump slip

  35. (Hysteresis) loop a a a contact angle volume advancing contact angle receding contact angle

  36. (Hysteresis) loop slip jump stick contact angle volume advancing contact angle receding contact angle

  37. Hysteresis: 3 dimensions A. squares 60o background 110o B. squares 110o background 60o

  38. Hysteresis: 3 dimensions A B squares hydrophilic squares hydrophobic

  39. Hysteresis: 3 dimensions macroscopic contact angle versus volume A B stick jump

  40. Hysteresis: 3 dimensions macroscopic contact angle versus volume A B 94o 92o 110/60

  41. Hysteresis on chemically patterned surfaces 1.Slip, stick, jump behaviour, but jumps at different volumes in different directions (but can be correlated) 2. Contact angle hysteresis different in different directions 3. Advancing angle (92o) bounded by qmax (110o) Receding angle (80o) bounded by qmin (60o) 4. Free energy balance between surface / drop interactions and interface distortions determines the hysteresis

  42. Summary The model Chemically patterned surfaces Spreading on stripes Hysteresis Superhydrophobic surfaces Introduction Hysteresis Transitions between states Dynamics

  43. Superhydrophobic surfaces

  44. Superhydrophobic surfaces

  45. Two drop states suspended drop collapsed drop He et al., Langmuir, 19, 4999, 2003

  46. Suspended and collapsed drops Suspended, q~160o Collapsed, q~140o Homogeneous substrate, qeq=110o