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Dynamics at Nano- and  Microfluidic Interfaces Geoff Willmott NZIP Conference 19 October 2011
<ul><li>Nano- and Microfluidics </li></ul><ul><li>Wetting: Capillaries, Droplets, Surfaces </li></ul><ul><li>Resistive Pul...
<ul><li>Fast Fluidic Microanalysis:  compact, portable, user friendly devices </li></ul><ul><li>Advantages: </li></ul><ul>...
Medical Device Technologies (MDT) MTANZ Report April 2011: Large global demand for MDT -  Aging population with rising rat...
Nanofluidics : The study and application of fluid flow in and around nanosized objects. Eijkel and van den Berg,  Microflu...
Interdisciplinary, Applied Eijkel and van den Berg,  Microfluid. Nanofluid.  1, 249 (2005)
Micro- and Nanofluidics:  Forces and Transport Inertia   - low Reynolds number, laminar flow Eijkel and van den Berg,  Mic...
<ul><li>Nano- and Microfluidics </li></ul><ul><li>Wetting: Capillaries, Droplets, Surfaces </li></ul><ul><li>Resistive Pul...
Thiolated, roughened copper Laurate solution  (applied to any surface) Substrates: Rod Stanley (IRL)  Contact angle > 160 ...
Splash
Capillary Uptake Experiments  Thanks Rod Stanley (IRL) for making the substrates: Larmour, Bell and Saunders,  Angew. Chem...
Classical Capillary Uptake No uptake if   c  > 90 °
Capillary + Droplet  Not widely studied in experiments Marmur,  J. Colloid Interf. Sci. , 209 ( 1988) Schebarchov and Hend...
Application: Drop-Based Microfluidics Baroud, Gallaire and Dangla,  Lab Chip  10, 2032 (2010) Kintses et al.,  Curr. Opin....
Inspiration: Bottom-Up! Schebarchov and Hendy,  Nano Letters  8, 2253 (2008) [Talk O14.1]
(1) Direction of non-wetting meniscus motion depends on drop size Willmott, Neto and Hendy,  Faraday Disc.  146, 233 (2010)
(1) Direction of non-wetting meniscus motion depends on drop size A bound on critical drop size for PTFE  - consistent wit...
(2) Laplace pressure can drive uptake when   c  > 90° PTFE capillary; drop radius 0.38 mm <ul><li>Borosilicate glass capi...
(3) Uptake Speed Depends on Drop Size Willmott, Neto and Hendy,  Soft Matter  7, 2357 (2011)
5 modes of interaction  Willmott, Neto and Hendy,  Faraday Disc. , 146, 233 (2010)
Uptake Enhanced by Detachment 0 ms 4.8 ms 0.8 ms 1.6 ms 2.4 ms 3.2 ms 4.0 ms
Uptake Enhanced by Detachment Direct correlation between pressure and meniscus motion with < 1 ms precision
Pressure Estimates Significant uncertainty: image analysis method Laplace:
A Can of Physics Worms  (i) Geometry:   - drop asphericity, pinning and dynamic shape change - tube entrance and interior ...
<ul><li>Nano- and Microfluidics </li></ul><ul><li>Wetting: Capillaries, Droplets, Surfaces </li></ul><ul><li>Resistive Pul...
“ Resistive Pulse Sensing” Membrane Electrolyte “ Translocations” +/- Current Time
Motivation: Duration & shape Magnitude Frequency Willmott et al.,  J. Phys. Cond. Matt.  22, 454116 (2010)
A Semi-Analytic Model:  R ( z 0 ) Homogeneous resistivity (assume: uniform electric field across width)
End Effects Artificial cone: ‘approximate’ or ‘estimate’ - cone pitch agrees with infinite half space result
End Effects: Important
FEM Comparison: On-Axis Bryan Smith (IRL Auckland):  Comsol 3.3, triangular mesh, ~ 60k degs freedom
Transport: Nernst-Planck for for  z 0 ( t ) Willmott et al.,  J. Phys. Cond. Matt.  22, 454116 (2010) DIFFUSION ELECTROKIN...
Result: Resistive Pulse Shape <ul><li>Parameters: </li></ul><ul><li>pH 8.0 </li></ul><ul><li>a  = 465 nm (fit) </li></ul><...
Summary of Assumptions  Homogeneous resistivity Artificial cone end effects Locally cylindrical Azimuthal symmetry Surface...
Electrophoretic Mobility of a Charged Particle Schoch, Han and Renaud,  Rev. Mod. Phys.  80, 839 (2008) a  -1 E v
Electrophoretic Mobility of a Charged Particle Smoluchowski + no curvature dependence Nanoparticle Detection and Charge Qu...
Thanks! Email: G.WILLMOTT@IRL.CRI.NZ Mike Arnold and  NMF team , esp. Rod Stanley (surfaces),  Bethan Parry, &  James ‘Elf...
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  1. 1. Dynamics at Nano- and Microfluidic Interfaces Geoff Willmott NZIP Conference 19 October 2011
  2. 2. <ul><li>Nano- and Microfluidics </li></ul><ul><li>Wetting: Capillaries, Droplets, Surfaces </li></ul><ul><li>Resistive Pulse Sensing </li></ul>Introduction
  3. 3. <ul><li>Fast Fluidic Microanalysis: compact, portable, user friendly devices </li></ul><ul><li>Advantages: </li></ul><ul><li>reduced volumes of sample and waste; power use </li></ul><ul><li>increased speed, resolution, control and safety </li></ul><ul><li>multifunctional/integrated devices </li></ul><ul><li>High Growth Areas: </li></ul><ul><li>pharmaceuticals; drug delivery </li></ul><ul><li>analytical/diagnostic devices </li></ul><ul><li>point of care </li></ul><ul><li>veterinary </li></ul><ul><li>food safety </li></ul><ul><li>biosecurity </li></ul>Microfluidics 1 4 5 2 3
  4. 4. Medical Device Technologies (MDT) MTANZ Report April 2011: Large global demand for MDT - Aging population with rising rates of chronic disease - $437 b globally, driven by the USA NZ has an emerging industry … - >$0.61 b revenues FY2010-11 with double-digit growth (wine approx $0.8 b) - 95% exports; <10% of NZ health expenditure is on devices - Good standard of clinicians and medical researchers - Innovative approach to primary health care … but faces challenges - $0.5 b of that revenue is F&P Healthcare - 165 skilled workers required in the next two years - 22 companies looking to raise $44 M capital
  5. 5. Nanofluidics : The study and application of fluid flow in and around nanosized objects. Eijkel and van den Berg, Microfluid. Nanofluid. 1, 249 (2005) Branton et al., Nature Biotechnology 26, 1146 (2008) D’Acunzi et al., Faraday Disc. 146, Paper #3 (2010) Schoch, Han and Renaud, Rev. Mod. Phys. 80, 839 (2008) Tas et al., Appl. Phys. Lett. 85, 3274 (2004)
  6. 6. Interdisciplinary, Applied Eijkel and van den Berg, Microfluid. Nanofluid. 1, 249 (2005)
  7. 7. Micro- and Nanofluidics: Forces and Transport Inertia - low Reynolds number, laminar flow Eijkel and van den Berg, Microfluid. Nanofluid. 1, 249 (2005) Viscosity Surface tension Electrostatics and electrokinetics Surface slip Molecular interactions (e.g. van der Waals, brush polymers) Geometry - because measurement is difficult!! Body forces (e.g. gravity, pressure)
  8. 8. <ul><li>Nano- and Microfluidics </li></ul><ul><li>Wetting: Capillaries, Droplets, Surfaces </li></ul><ul><li>Resistive Pulse Sensing </li></ul>Introduction
  9. 9. Thiolated, roughened copper Laurate solution (applied to any surface) Substrates: Rod Stanley (IRL) Contact angle > 160  Superhydrophobic Surfaces
  10. 10. Splash
  11. 11. Capillary Uptake Experiments Thanks Rod Stanley (IRL) for making the substrates: Larmour, Bell and Saunders, Angew. Chem. Int. Edit. , 1710 (2007) Willmott, Neto and Hendy, Soft Matter 7, 2357 (2011); Faraday Discuss. 146, 233 (2010) <ul><li>PTFE capillary (i.d. 300  m) - drop on a superhydrophobic surface - slowly brought into contact </li></ul>
  12. 12. Classical Capillary Uptake No uptake if  c > 90 °
  13. 13. Capillary + Droplet Not widely studied in experiments Marmur, J. Colloid Interf. Sci. , 209 ( 1988) Schebarchov and Hendy, Phys Rev E 78, 046309 (2008)
  14. 14. Application: Drop-Based Microfluidics Baroud, Gallaire and Dangla, Lab Chip 10, 2032 (2010) Kintses et al., Curr. Opin. Chem. Biol. 14, 548 (2010) Generation Merging
  15. 15. Inspiration: Bottom-Up! Schebarchov and Hendy, Nano Letters 8, 2253 (2008) [Talk O14.1]
  16. 16. (1) Direction of non-wetting meniscus motion depends on drop size Willmott, Neto and Hendy, Faraday Disc. 146, 233 (2010)
  17. 17. (1) Direction of non-wetting meniscus motion depends on drop size A bound on critical drop size for PTFE - consistent with contact angle 107.8  - 110.6  Willmott, Neto and Hendy, Faraday Disc. , 146, 233 (2010)
  18. 18. (2) Laplace pressure can drive uptake when  c > 90° PTFE capillary; drop radius 0.38 mm <ul><li>Borosilicate glass capillary (diameter 100 micron) </li></ul><ul><li>Silanized: contact angle of internal surface with water ~110  </li></ul>Willmott, Neto and Hendy, Soft Matter 7, 2357 (2011)
  19. 19. (3) Uptake Speed Depends on Drop Size Willmott, Neto and Hendy, Soft Matter 7, 2357 (2011)
  20. 20. 5 modes of interaction Willmott, Neto and Hendy, Faraday Disc. , 146, 233 (2010)
  21. 21. Uptake Enhanced by Detachment 0 ms 4.8 ms 0.8 ms 1.6 ms 2.4 ms 3.2 ms 4.0 ms
  22. 22. Uptake Enhanced by Detachment Direct correlation between pressure and meniscus motion with < 1 ms precision
  23. 23. Pressure Estimates Significant uncertainty: image analysis method Laplace:
  24. 24. A Can of Physics Worms (i) Geometry: - drop asphericity, pinning and dynamic shape change - tube entrance and interior (ii) Entrance dynamics: - meniscus reorientation - prelinear inertial acceleration - viscous flow (iii) Surfaces: - Pinning due to chemical / physical heterogeneity - The non-wetting dynamic contact angle (iv) Pre-filled capillaries: - Incl. ‘jet’ vs ‘sink’ flow for filling/drainage applications (v) Electrokinetics: - Electroviscosity and double layer structure (vi) Close to 100 nm: - violation of the non-slip boundary condition - thermal capillary waves - disjoining pressure - thin film precursors to wetting - nanobubbles
  25. 25. <ul><li>Nano- and Microfluidics </li></ul><ul><li>Wetting: Capillaries, Droplets, Surfaces </li></ul><ul><li>Resistive Pulse Sensing </li></ul>Introduction
  26. 26. “ Resistive Pulse Sensing” Membrane Electrolyte “ Translocations” +/- Current Time
  27. 27. Motivation: Duration & shape Magnitude Frequency Willmott et al., J. Phys. Cond. Matt. 22, 454116 (2010)
  28. 28. A Semi-Analytic Model: R ( z 0 ) Homogeneous resistivity (assume: uniform electric field across width)
  29. 29. End Effects Artificial cone: ‘approximate’ or ‘estimate’ - cone pitch agrees with infinite half space result
  30. 30. End Effects: Important
  31. 31. FEM Comparison: On-Axis Bryan Smith (IRL Auckland): Comsol 3.3, triangular mesh, ~ 60k degs freedom
  32. 32. Transport: Nernst-Planck for for z 0 ( t ) Willmott et al., J. Phys. Cond. Matt. 22, 454116 (2010) DIFFUSION ELECTROKINETICS PRESSURE (CONVECTION) OTHER …
  33. 33. Result: Resistive Pulse Shape <ul><li>Parameters: </li></ul><ul><li>pH 8.0 </li></ul><ul><li>a = 465 nm (fit) </li></ul><ul><li>b = 16.1  m (fit) </li></ul><ul><li>d = 150  m </li></ul><ul><li>a’ = 110 nm </li></ul><ul><li>0.3 V applied </li></ul><ul><li>= 0.86  m </li></ul><ul><li>q = -1.54 x 10 -3 C m -2 </li></ul>Willmott and Parry, J. Appl. Phys , DOI: 10.1063/1.3580283 (2011) Half max
  34. 34. Summary of Assumptions Homogeneous resistivity Artificial cone end effects Locally cylindrical Azimuthal symmetry Surface charges and electro-osmosis Electrode and electronic effects Particle on-axis Spherical particle Quasi-static Simplified drag in confinement Other transport insignificant
  35. 35. Electrophoretic Mobility of a Charged Particle Schoch, Han and Renaud, Rev. Mod. Phys. 80, 839 (2008) a  -1 E v
  36. 36. Electrophoretic Mobility of a Charged Particle Smoluchowski + no curvature dependence Nanoparticle Detection and Charge Quantification Using Tunable Nanopores: Poster 9 Drag + Gauss … point charge <ul><li>Calculation of “effective charge” based on 2 nd (classical) method </li></ul><ul><li>Expect for constant surface charge, so </li></ul><ul><li>… conceptual difficulty for measurements? </li></ul>
  37. 37. Thanks! Email: G.WILLMOTT@IRL.CRI.NZ Mike Arnold and NMF team , esp. Rod Stanley (surfaces), Bethan Parry, & James ‘Elf’ Eldridge (qNano) U.Syd. : Chiara Neto (surfaces) ESR : Michael Taylor (HSP) Izon Science esp. Robert Vogel, Ben Glossop, Hans van der Voorn U of Q Collaborators
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