Post on 03-Nov-2018
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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
viscosity resists Hagen-‐Poiseuille
spherical-‐cap response
V
P
Poincare Newton Chandrasekhar Jacobi Euler Liouville
dynamical-system
9
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
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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sessile-drop recap
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• spectra split for • damped (effec6ve dissipa6on) for
[3,3] mode
side
CT Video here
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