Nearly-zero contact angle hysteresis on lubricated surfaces Dan Daniel, IMRE, A*STAR
2011
1 mm
Oleoplaning droplets on lubricated surfaces
lubricant film lubricant film
2011
Lubricated
repels blood …
and crude oil
2005
“Slippery composite surface” that is “hemi-solid, hemi-liquid” with “non-measurable” contact angle-hysteresis.
2005
“Slippery composite surface” that is “hemi-solid, hemi-liquid” with “non-measurable” contact angle-hysteresis. Lubricated surfaces, a rose by any other name … SLIPS, LIS, Slippery pre-suffused surfaces, LubiSS
Outline Static: droplet shape and geometry Dynamic: oleoplaning droplet with nearly-zero hysteresis Comparison with lotus-effect surface Thoughts/Open questions
Static droplet: contact angle
θapp θapp ~ 100ο for water
Static droplet: contact angle no cloaking
with cloaking
γl < γlο + γο
γl > γlο + γο
θapp θapp ~ 100ο for water
Static droplet: contact angle no cloaking
with cloaking
γl < γlο + γο
γl > γlο + γο
θapp θapp ~ 100ο for water
Modified Young’s Equation cos θapp = (γο – γlο)/ γeff γeff = γl or γlο + γo no/with cloaking
Static droplet: contact angle no cloaking
with cloaking
γl < γlο + γο
γl > γlο + γο
θapp θapp ~ 100ο for water
Modified Young’s Equation cos θapp = (γο – γlο)/ γeff γeff = γl or γlο + γo no/with cloaking Independent of micro-/nano-structures
Static droplet: contact angle
Data from Wong et al, Nature, 2011 Schellenberger et al, Soft Matter, 2015
Static droplet: contact angle
no cloaking Data from Wong et al, Nature, 2011 Schellenberger et al, Soft Matter, 2015
with cloaking
Static droplet: nm lubricant film γsl > γso + γlo and repulsive A > 0
l
o s
thin film interference
Static droplet: nm lubricant film γsl > γso + γlo and repulsive A > 0
rext
rint
thin film interference
low pressure in ridge
|ΔP| ≈ γo/rext ≈ γlo /rint
Static droplet: nm lubricant film γsl > γso + γlo and repulsive A > 0
25 nm rext
rint
thin film interference
low pressure in ridge
|ΔP| ≈ γo/rext ≈ γlo /rint
balanced by h ~ (r A/ γ)1/3 tens of nm
Π ≈ A/6πh3
Disjoining pressure
Static droplet: nm lubricant film on top of posts
speed 4x nm film
40 um
film thickness set by post heights
no contact line pinning
Comparison with lotus-effect surfaces
speed 4x
50 um
air film instead of lubricant film
with contact line pinning
Droplet oleoplanes with Landau-Levich film static
dynamic
U rint hLLD ~ nm film
~ um film hLLD ~ rint (ηU/γlo)2/3 = rint Ca2/3
rext
Droplet oleoplanes with Landau-Levich film static
dynamic
U rint hLLD ~ nm film
~ um film hLLD ~ rint (ηU/γlo)2/3 = rint Ca2/3 = (γlo / γo) rext Ca2/3
rext
Droplet oleoplanes with Landau-Levich film static
dynamic
U rint hLLD h = hp
h > hp hLLD ~ rint (ηU/γlo)2/3 = rint Ca2/3 = (γlo / γo) rext Ca2/3
rext
Droplet oleoplanes with Landau-Levich film
stationary hfilm = hp
moving hfilm = hLLD
0.1 mm
stop motion hfilm à hp
Droplet oleoplanes with Landau-Levich film dynamic
U
F ~ ηoU/hLLD (2a l ) = 2aγlo Ca2/3
rint hLLD
Viscous dissipation in transition region l ~ rint Ca1/3
l
Droplet oleoplanes with Landau-Levich film dynamic
U
F ~ ηoU/hLLD (2a l ) = 2aγlo Ca2/3
rint hLLD
Viscous dissipation in transition region l ~ rint Ca1/3
l Viscous dissipation in wetting ridge (Tanner’s law) θw ~ Ca1/3 θw
F ~ (ηoU / θw) 2a = 2aγ Ca2/3 o Keiser et al, Soft Matter, 2017
Custom-built force sensor to measure dissipation force F = k Δx 2 μl droplet, U = 0.3 mm/s
U
Δx
Contact angle hystersis Δcos θ ~ Ca2/3
F/2aγ
F ~ ηoU/hLLD (2a l ) = 2aγlo Ca2/3
Ca
Contact angle hystersis Δcos θ ~ Ca2/3
F/2aγ
F ~ ηoU/hLLD (2a l ) = 2aγlo Ca2/3 Δcos θ = F/ 2aγl = (γlo / γl) F/ 2aγlo ~ Ca2/3 Ca
Contact angle hystersis Δcos θ ~ Ca2/3
F/2aγ
F ~ ηoU/hLLD (2a l ) = 2aγlo Ca2/3 Δcos θ = F/ 2aγl = (γlo / γl) F/ 2aγlo ~ Ca2/3 Ca Δcos θ à 0, Ca à 0 Nearly zero hysteresis No contact line pinning
Custom-built force sensor currently at IMRE, A*STAR
light camera
Interference Microscopy vibration-free
Comparison with lotus-effect surfaces
Contact line pinning on lotus-effect surface
100 um
Contact line pinning on lotus-effect surface
Micro-droplets after breakup of capillary bridges
F independent of U for lotus-effect surfaces
F independent of U for lotus-effect surfaces
Δcos θ > 0, Ca à 0 finite hysteresis
Results presented can be found in D. Daniel, J.V.I Timonen, R. Li, S.J. Velling and J. Aizenberg “Oleoplaning droplets on lubricated surfaces” Nat. Phys. 2017 D. Daniel+, J.V.I Timonen, R. Li, S.J. Velling, M.J. Kreder, A. Tetreault and J. Aizenberg+ “Origins of extreme liquid repellency on structured, flat, and lubricated surfaces” in revision to Phys. Rev. Lett. (and ArXiv) +co-corresponding authors M.J. Kreder*, D. Daniel*, A. Tetreault , Z. Cao, B. Lemaire, J.V.I Timonen and J. Aizenberg “Film dynamics and lubricant depletion by droplets moving on lubricated surfaces” in revision to Phys. Rev. X *co-first authors
Useful literature A. Keiser, L. Keiser, C. Clanet and D. Quere “Drop friction on liquid infused surfaces” Soft Matter 2017 M. Tress, S. Karpitschka, P. Papadopoulos, J. H. Snoeijer, D. Vollmer and H.-J. Butt “Shape of a sessile drop on a flat surface covered with a liquid film” Soft Matter 2017 F. Schellenberger et al “Direct observation of drops on slippery lubricant-infused surfaces ” Soft Matter 2015 J. D. Smith et al “Droplet mobility on lubricant-impregnated surfaces ” Soft Matter 2013 A. Lafuma and D. Quere “Slippery pre-suffused surfaces.” Euro. Phys. Lett. 2011
Thoughts and open questions
Contact angle hysteresis for high Ca
our work
Keiser et al, 2017
Keiser et al, Soft Matter, 2017
Contact angle hysteresis for different initial film thicknesses Dissipa0ve force for different lubricant heights
3.0
0.5 μm
Fd (μN)
2.5
3 μm
2.0 1.5 1.0 h = 0.5 um h = 3 um h = 6 um
0.5 0.0 0.0
0.2
0.4 0.6 U (mm/s)
0.8
1.0
Δcos θ ~ Ca2/3 independent of initial h for thick micron-film
6 μm
Contact angle hysteresis for different initial film thicknesses Dissipa0ve force for different lubricant heights
3.0
0.5 μm
Fd (μN)
2.5
3 μm
2.0 1.5 1.0 h = 0.5 um h = 3 um h = 6 um
0.5 0.0 0.0
0.2
0.4 0.6 U (mm/s)
0.8
1.0
Δcos θ ~ Ca2/3 independent of initial h for thin nano-film ?
6 μm
Contact angle hysteresis for structured surfaces with thin nano-film ?
Dai et al, ACS Nano, 2015 Slippery Wenzel State
Thanks to …
Prof. J. Aizenberg
M. J. Aizenberg
R. Li
S. J. Velling
Prof. J. V. I. Timonen
A. Tetreault
Prof. Bob. E Cohen
Prof. Paul V. Braun
I can be contacted at
[email protected] http://dandaniel.me/