The document discusses electrified liquid-liquid interfaces from both a theoretical and applications perspective. It begins by covering concepts like Debye screening and the structure of electric double layers that form at electrolyte interfaces. It then discusses theories of electrowetting, where an applied electric field can change the shape of a liquid interface. Challenges with electrowetting on dielectric systems are noted due to high operating voltages. Interfaces between two immiscible electrolyte solutions are also discussed, which could enable ultra-low voltage electrowetting. Equilibrium theories of electrowetting at these types of interfaces are presented.
23. Electrowetting
The area of a liquid/fluid interface changes as a result of an
applied electric field.
G. Lippmann(1875)
−
Electrocapillarity: electrostatic charge
modifies capillary forces
∂γ
∂Φ = −Q
A
+
24. Electrowetting
The area of a liquid/fluid interface changes as a result of an
applied electric field.
G. Lippmann(1875)
−
Electrocapillarity: electrostatic charge
modifies capillary forces
∂γ
∂Φ = −Q
A
A. Frumkin(1930)
Chemical reactions at electrode surface, Hg
electrode
+
25. Electrowetting
The area of a liquid/fluid interface changes as a result of an
applied electric field.
G. Lippmann(1875)
Electrocapillarity: electrostatic charge
modifies capillary forces
∂γ
∂Φ = −Q
A
A. Frumkin(1930)
+ +
Chemical reactions at electrode surface, Hg
electrode
+++++
26. Electrowetting
The area of a liquid/fluid interface changes as a result of an
applied electric field.
G. Lippmann(1875)
Electrocapillarity: electrostatic charge
modifies capillary forces
∂γ
∂Φ = −Q
A
A. Frumkin(1930)
+ +
Chemical reactions at electrode surface, Hg
electrode
B. Berge(1993)
+++++
Polymer coating for applications - ewod
36. ewod
challenges
• Practical
• Electric field divergence ⇒ dielectric coating ⇒ large
operation voltages (20 V) (CD Cdl )
• Theoretical - not thoroughly developed
37. ewod
challenges
• Practical
• Electric field divergence ⇒ dielectric coating ⇒ large
operation voltages (20 V) (CD Cdl )
• Theoretical - not thoroughly developed
• Electric field divergence ⇒ full analytical solution does not
exist
• Contact angle saturation
• No satisfactory model of dynamics
46. Electrowetting with ities
equilibrium theory
∆G = [γde − γse + εde − εse ] Ade + [γds + εds ] Ads + Vd ∆p
¯ ¯ ¯
− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −
> (ds): 2 x Cdl in series
> (de), (se): Cdl , Cil in series α
+ + + + + + + + + + + + + + + + + + + ++ + + + + + + + + + + + +
> spherical, macroscopic droplet
Minimisation G(α) ⇒ α(V)
→ large contact angle variation Φ < 1 V
C. Monroe, M. Urbakh, A. Kornyshev. J. Electrochem. Soc., 156(2009)
47. Electrowetting with ities
equilibrium theory
∆G = [γde − γse + εde − εse ] Ade + [γds + εds ] Ads + Vd ∆p
¯ ¯ ¯
− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −
> (ds): 2 x Cdl in series
> (de), (se): Cdl , Cil in series α
+ + + + + + + + + + + + + + + + + + + ++ + + + + + + + + + + + +
> spherical, macroscopic droplet
Minimisation G(α) ⇒ α(V)
→ large contact angle variation Φ < 1 V
→ effect of α0
C. Monroe, M. Urbakh, A. Kornyshev. J. Electrochem. Soc., 156(2009)
48. Electrowetting with ities
equilibrium theory
∆G = [γde − γse + εde − εse ] Ade + [γds + εds ] Ads + Vd ∆p
¯ ¯ ¯
− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −− −
> (ds): 2 x Cdl in series
> (de), (se): Cdl , Cil in series α
+ + + + + + + + + + + + + + + + + + + ++ + + + + + + + + + + + +
> spherical, macroscopic droplet
Minimisation G(α) ⇒ α(V)
→ large contact angle variation Φ < 1 V
→ effect of α0 ,c
C. Monroe, M. Urbakh, A. Kornyshev. J. Electrochem. Soc., 156(2009)
49. Electrowetting with ities
experiment
A. Kucernak(2010)
> non-ideal electrode ⇒ hysteresis
> new pulsing technique
A. Kornyshev, A. Kucernak, M. Marinescu, C. Monroe, A. Sleightholme, M. Urbakh. J. Phys. Chem. C, in print
50. Electrowetting with ities
experiment
A. Kucernak(2010)
> non-ideal electrode ⇒ hysteresis
> new pulsing technique
A. Kornyshev, A. Kucernak, M. Marinescu, C. Monroe, A. Sleightholme, M. Urbakh. J. Phys. Chem. C, in print
51. Electrowetting with ities
experiment
A. Kucernak(2010)
> non-ideal electrode ⇒ hysteresis
> new pulsing technique
A. Kornyshev, A. Kucernak, M. Marinescu, C. Monroe, A. Sleightholme, M. Urbakh. J. Phys. Chem. C, in print
52. Electrowetting with ities
experiment
A. Kucernak(2010)
> non-ideal electrode ⇒ hysteresis
> new pulsing technique
• eliminate hysteresis
• strong α(V) dependence
• stick-slip motion, step size
A. Kornyshev, A. Kucernak, M. Marinescu, C. Monroe, A. Sleightholme, M. Urbakh. J. Phys. Chem. C, in print
53. Electrowetting with ities
experiment
A. Kucernak(2010)
> non-ideal electrode ⇒ hysteresis
> new pulsing technique
• eliminate hysteresis
• strong α(V) dependence
electric pulsing ←→ effect of
• stick-slip motion, step size
roughness?
A. Kornyshev, A. Kucernak, M. Marinescu, C. Monroe, A. Sleightholme, M. Urbakh. J. Phys. Chem. C, in print
54. Electrowetting with ities
theory of pulsing R(t)
¨
Ff + Fd = mR
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
55. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
56. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
57. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
k(V ) = ∂ 2 G/∂R2
Re (V )
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
58. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
k(V ) = ∂ 2 G/∂R2
Re (V )
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
59. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
k(V ) = ∂ 2 G/∂R2
Re (V )
→ qualitative success
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
60. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
k(V ) = ∂ 2 G/∂R2
Re (V )
→ qualitative success
→ need better system characterisation
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
61. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
k(V ) = ∂ 2 G/∂R2
Re (V )
→ qualitative success
→ need better system characterisation
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
62. Electrowetting with ities
theory of pulsing R(t)
Ff + Fd = mR¨
¨ ˙ ˙
mR + η R = k(Re − R) − F0 sign(R)
k(V ) = ∂ 2 G/∂R2
Re (V )
→ qualitative success
→ need better system characterisation
F0 F0
→ F0 ⇒ Re − k , Re + k metastable
M. Marinescu, M. Urbakh, T. Barnea, A. Kucernak, A. Kornyshev. J. Phys. Chem. C, submitted
63. Electrowetting with ities
remarks
• Theoretical description the dynamics of electrowetting
• Ultra-low electrowetting with ities is real
64. Electrowetting with ities
remarks
• Theoretical description the dynamics of electrowetting
• Ultra-low electrowetting with ities is real
• Pulsing technique
− tool for facilitating electrowetting
− a new electroanalytical method for wetting dynamics
65. Electrowetting with ities
remarks
• Theoretical description the dynamics of electrowetting
• Ultra-low electrowetting with ities is real
• Pulsing technique
− tool for facilitating electrowetting
− a new electroanalytical method for wetting dynamics
• Current focus on minimising F0 (A. Kucernak, N. Cousens)
79. Functionalised ities
remarks
Theory for coverage, reflection/transmission - awaits
experimental proof
Theory of Faraday rotation - in work
Magnetic properties (spin, ferrofluids) - planned
Beyond ities:
Functionalise electrolyte/electrode interface(E-Ink)
85. Fundamental constants
Name Value Units Expression
ε0 8.854 · 10−12 F/m
kB 1.381 · 1023 J/K
8.617 · 10−5 eV/K
e 1.602 · 10−19 C
NA 6.022 · 1023 1/mol
F 9.648 · 104 C/mol NA e
R 8.314 J/(mol K) kB NA
LB 7 · 10−10 ( ) m e2 /(4πε0 εkB T )
kB T @RT 4.11 · 10−21 J
0.026 eV
( ) for ε = 80, water @ RT