Wetting, spreading & capillary adhesion: putting shape-instability to purpose

1  11/23/2010  

Paul  Steen  Cornell  University  

Chemical  Engineering  

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Collaborators    Dominik  Barz  Susan  Daniel  Peter  Ehrhard  Amir  Hirsa  Monika  Nitsche  Kyra  Stephanoff  Mike  Vogel  XiuMei  Xu    D  Anderson  S  Grice  

PhD  Students   AL  AlLeri  JB  Bostwick  CT  Chang  BL  Cox  AM  Macner  DM  Slater  HB  van  Lengerich    Cornell  Fluids  

Colleagues  

acknowledgments

Sponsors   NASA  NSF  DARPA  

Eisner & Aneshansley, “Defense by foot adhesion in a beetle”, PNAS 97(12) 2000

as Mother Nature teaches !

BBC ‘Secret Weapons’

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1 mm

attack

10 mµ

defense

50 m

Eisner & Aneshansley, “Defense by foot adhesion in a beetle”, PNAS 97(12) 2000

the beetle’s feat

surface tension

4

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1Adhesion StrengthDroplet Radius

∝

favorable scaling

Q. a man-made device based on perimeter-packing?

macroscale

grab/release concept 1.7 mm tube

diameter

Aluminum foil

lab demo

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capillary coarsening

time

ini6al  

final  -­‐  equilibrium  

van  Lengerich,  Vogel,  PHS,  PRE  

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Q. can passive design mitigate coarsening?

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viscosity  resists  Hagen-­‐Poiseuille  

spherical-­‐cap  response  

V  

P  

Poincare Newton  Chandrasekhar Jacobi Euler Liouville

dynamical-system

9  

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coarsening rates

capillary coarsening recap

 •  neighbors  compete,  self-­‐similarity  

•  no  ‘signature’  for  defec6ve  pads  

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Q. how to make switchable (active)?

Electrodes

Glass frit

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A. electro-osmotic pumping e.g.      Zeng,  S,  Chen,  C.-­‐H,  Mikkelson,  J.  C.  &  SanLago,  J.  G.  (2001)  

probing the barrier

1.7 mm V = 10 Volts

Droplet 1 Droplet 2

PHS, Vogel, Ehrhard, Proc Nat Acad Sci, 2005.

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adhesion device

Electrodes

Glass frit Test plate

Reservoir

Vogel, PHS, Proc Nat Acad Sci, 2010.

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500 mm

big-­‐mac  device  performance  

Linoleum: 700 mg

Plywood: 725 mg

Brick: 670 mg Sandpaper (150 grit): 650 mg Roof shingle: 675 mg

shown tested here

also tested successfully

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silicon-­‐wafer  device  

Glass frit pump (device thickness ~ 5 mm, mass ~ 4 g)

e = 500, 300 (or 150 mm)

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average force measure

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A. perimeter-packing achieved!

Vogel, PHS, Proc Nat Acad Sci, 2010.

literature Theory   ComputaLon   Experiment  

Rodot  et  al.  (1979)  

Bauer  &  Chiba  (04,  05)  

Strani  &  Sabeba  (84,  88)  

Ganan  &  Barerro  (90)  

Lyubimov  et  al.  (04,  06)  Fayzrakhmanova  &  Straube  (09)  

Basaran  &  DePaoli,  94  DePaoli  et  al.  (95)  Wilkes  &  Basaran,  01  James  et  al.  (03)  

James  et  al.  (03)  

Vukasinovic  et  al.  (07)  

Noblin  et  al.  (04)  Daniel  et  al.  (04)  

Brunet  et  al.  (09)  

Couder  et.  al  (05)  

droplet manipulation

   Daniel  et.  al  04  

Smith  et.  al  2007  Noblin  et.  al  09  

Couder  et.  al  05  

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Q.  natural  frequencies?  

Rayleigh oscillations

sphere radius liquid density

surface tension

k = 0, 1, 2, . . .

spectrum

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spherical-cap base-state w/ ‘Hocking’ spreading

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mobile pinned

U

1  

Hocking condition

Hocking,  JFM  1977  Davis,  JFM  1980  

classify mode shapes

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k=1 k=2 k=3 k=4 k=5 k=6 k=7 k=8 k=9

l=0

l=1

l=2

l=3

l=4

l=5

l=6

l=7

l=8

l=9

classify mode shapes

(a0,L) = (90o,0)  

spectrum

(a0,L) = (90o,0)  

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Λ

α0  

90o  

∞ 0 0o  

180o  

60o  

spectrum

unfolding of spectra

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sessile-drop recap

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•  spectra  split  for    •  damped  (effec6ve  dissipa6on)  for    

[3,3]  mode  

side  

CT  Video  here  

top  

•  beetle lessons –  perimeter-packing, switchable

•  coarsening & coalescence mitigation –  passive design

•  grab-release device w/ eo pump –  perimeter-packing, switchable adhesion

•  sessile-drop oscillations –  spectral splitting

 

concluding  remarks  

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