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Microfluidic Free-Surface Flows: Simulation and Application

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  1. Microfluidic Free-Surface Flows: Simulation and Application The University Of Birmingham J.E Sprittles Y.D. Shikhmurzaev Indian Institute of Technology, Mumbai November 5th 2011

  2. Worthington 1876 – First Experiments

  3. Worthington’s Sketches Millimetre sized drops of milk on smoked glass.

  4. Millimetre Drop Impact 1 2 3 4 Courtesy of Romain Rioboo

  5. Flow Control Using Chemically Patterned Solids Hydrophobic Hydrophilic

  6. Inkjet Printing: Impact of Microdrops • 100 million printers sold yearly in graphic arts. • Drops ejected have: • Radius ~ 10microns • Impact ~ 10m/s • Surface physics are dominant. • Inkjet printing is now replacing traditional fabrication methods...

  7. Polymer – Organic LED (P-OLED) Displays

  8. Inkjet Printing of P-OLED Displays Microdrop Impact & Spreading

  9. Why Develop a Model? • - Recover Hidden Information • - Map Regimes of Spreading 3 – Experiment Rioboo et al (2002) Dong et al (2002)

  10. Previous Modelling of Drop Spreading Phenomena

  11. The Contact Angle • Contact angle is required as a boundary condition for the free surface shape. r r t Pasandideh-Fard et al 1996

  12. Conventional Approach – Contact Angle ) U Dynamic Contact Angle Formula Young Equation σ1 σ3 - σ2 Assumption: A unique angle for each speed R

  13. Is the Angle Always a Function of the Speed?(Experiments of Bayer & Megaridis 06) 1mm Water )

  14. Hydrodynamic Assist to Wetting U U, cm/s Controlled Flow Rate Blake & Shikhmurzaev 02

  15. Specific Physics of Wetting: Interface Formation

  16. The Simplest Model of Interface Formation (Shikhmurzaev 93) In the bulk: Interface Formation Model Conventional Model On free surfaces: On liquid-solid interfaces: At contact lines:

  17. Numerical Simulation of Drop Impact and Spreading Phenomena

  18. Graded Mesh – For Both Models

  19. The Spine Method for Free Surface Flows Nodes define free surface. The Spine Nodes fixed on solid.

  20. Arbitrary Lagrangian-Eulerian Mesh Design • Spines are Bipolar • Free Surface Captured Exactly JES & YDS 2011, Int. J. Num. Meth. Fluids ; JES & YDS 2011, Submitted to J. Comp. Phys.

  21. Oscillating Drops: Code Validation For Re=100, f2 = 0.9 JES & YDS 2011, MNF, In Print

  22. Oscillating Drops: Code Validation a b

  23. Removal of Spurious Pressure

  24. Pressure Behaviour for Obtuse Angles The pressure plot from a typical simulation.

  25. Testing Ground: Flow in a Corner U U In frame moving with contact line. In frame fixed with solid.

  26. Viscous Flow in a Corner Spurious COMSOL ‘Solution’ Our FEM Solution JES & YDS 2011, IJNMF 65; JES & YDS 2011, CMAME 200

  27. Results

  28. Microdrop Spreading from Rest(Capillarity Driven Spreading) Pressure Scale Apex Velocity Scale Capillary Wave

  29. Microdrop Impact and Spreading Pressure Scale Velocity Scale

  30. Speed – Angle Relationships:Comparison of IFM with Conventional Model. Jump in Contact Line Speed Rest (IFM) Increase in Contact Line Speed Impact (IFM) Conventional Model. 0.01 1 100 Jiang et al 79

  31. Typical Microdrop Experiment (Dong et al 07) ? ?

  32. Early Stages of Spreading 2.2 m/s 4.4 m/s 12.2 m/s

  33. Recovering Hidden Information

  34. Influence of Wettability

  35. Surfaces of Variable Wettability 1 1.5

  36. Impact on a Surface of Variable Wettability 4m/s Impact 5m/s Impact

  37. Current/Future Work & Possible Avenues for Collaboration

  38. Current Research: Dynamics at Different Scales Millimetre Drop Microdrop Nanodrop

  39. Current Research:Unexplained Phenomena in Coating Processes Ca Simpkins & Kuck 03

  40. Current Research: Nanofluidics “While inertial effects may also be important, the influence of the dynamic contact angle should not be ignored.” (Martic et al 02)

  41. Future Research: Pore Scale Dynamics Wetting Mode Threshold Mode

  42. Future Research: Additional Physical Effects Liquid-Liquid Displacement Surfactant Transport

  43. Future Research: Impact on Powders Mitchinson (2010) Marston et al (2010) Aussillous & Quéré (2001)

  44. Future Research: Complex Capillary Phenomena

  45. Thanks

  46. Qualitative Test: Pyramidal Drops (mm size drop) Experiment Renardy et al.

  47. Future Research: Multi-Physics Platform ) • Multiphysics Platform + • Dynamic Wetting Patch

  48. Hysteresis of the Dynamic Contact Angle • Hyteresis: Receding angle • No hysteresis

  49. Analytic Progress: When Does ? High Impact Speed Small Drops Stokes Region (viscous forces dominate inertial forces) Length of interface formation process Slow Spreading of Large Drops