Interfacial microrheology of phospholipid monolayers at the - - PowerPoint PPT Presentation

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ISSP soft matter 2010 Interfacial microrheology of phospholipid monolayers at the air/water Interface Siyoung Choi K. Kim, J. Zasadzinski, T. Squires University of California, Santa Barbara Motivation Science Engineering Cell membrane

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SLIDE 1

Interfacial microrheology

  • f phospholipid monolayers

at the air/water Interface

Siyoung Choi

  • K. Kim, J. Zasadzinski, T. Squires

University of California, Santa Barbara ISSP soft matter 2010

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SLIDE 2

Lung surfactants High Internal Phase Emulsion(PS-P2VP) Kramer group (2003) Zasadzinski group (2003)

Cell membrane Coating Process Shampoo, detergents, etc. Foams

Science Engineering

Motivation

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SLIDE 3

Interfacial viscoelasticity

A magnetic needle at the air/water Interface

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SLIDE 4

Interfacial viscoelasticity

A magnetic needle at the air/water Interface A few drops of water-insoluble surfactants

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SLIDE 5

Systems we are working on

DPPC (phospholipid) DPPC +Chol (60:40) Colloidal crystal at the oil/water interface

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SLIDE 6

Systems we are working on

DPPC (phospholipid) DPPC +Chol (60:40) Colloidal crystal at the oil/water interface

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SLIDE 7

Systems we are working on

DPPC (phospholipid) DPPC +Chol (60:40) Colloidal crystal at the oil/water interface

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SLIDE 8

Systems we are working on

DPPC (phospholipid) DPPC +Chol (60:40) Colloidal crystal at the oil/water interface

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SLIDE 9

Viscometry of 2D interfaces

s

  • a

s : surface viscosity : subphase viscosity a : disk radius P : Contact perimeter to 2D surface A : Contact Area to bulk phase

High perimeter/area ratio: higher sensitivity High aspect ratio (e.g. needles – Brooks, Fuller,

Vermant, Fischer, Zasadzinski …) Small probes (microrheology – Sickert & Rondelez, Fischer, Dai, Weeks, …)

“Boussinesq Number” High aspect ratio (e.g. needles - Brooks, Fuller, Vermant, Fischer, Zasadzinski, ...) Small probes (microrheology - Weeks, Sickert & Rondelez, Fischer, Dai, ...

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SLIDE 10

General Experimental Procedure

DATA acquisition board microscope Camera Image analysis Angular strain(t) (Red) Magnetic torque(t) (Green) electromagnets interface subphase

Applied Torque ~ Stress Rotational displacement ~ Strain

Imposed oscillatory magnetic field Can compute viscoelasticity(G’, G’’)

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SLIDE 11

General Experimental Procedure

DATA acquisition board microscope Camera Image analysis Angular strain(t) (Red) Magnetic torque(t) (Green) electromagnets interface subphase

Applied Torque ~ Stress Rotational displacement ~ Strain

Imposed oscillatory magnetic field Can compute viscoelasticity(G’, G’’) Imposed constant stress Can measure Creep compliance--J(t)

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SLIDE 12

Janus ferromagnetic microprobes

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SLIDE 13

Janus ferromagnetic microprobes

requirements

  • Small, yet visible
  • Ferromagnetic
  • Amphiphilic
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SLIDE 14

Janus ferromagnetic microprobes

Photolithography

requirements

  • Small, yet visible
  • Ferromagnetic
  • Amphiphilic
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SLIDE 15

Janus ferromagnetic microprobes

Photolithography

Photoresist (~ 1 um) Ni/Co (~100 nm) Au (~10 nm) Thiol monolayer

requirements

  • Small, yet visible
  • Ferromagnetic
  • Amphiphilic
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SLIDE 16

Janus ferromagnetic microprobes

Photolithography

20μm diameter 1μm tall

20µm

bright field image Amphiphilic - Janus

Photoresist (~ 1 um) Ni/Co (~100 nm) Au (~10 nm) Thiol monolayer

requirements

  • Small, yet visible
  • Ferromagnetic
  • Amphiphilic
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SLIDE 17

Janus ferromagnetic microprobes

Photolithography

20μm diameter 1μm tall

20µm

bright field image Amphiphilic - Janus Size, Shape, Magnetic and Surface properties

Control over

Photoresist (~ 1 um) Ni/Co (~100 nm) Au (~10 nm) Thiol monolayer

requirements

  • Small, yet visible
  • Ferromagnetic
  • Amphiphilic
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SLIDE 18

I + + k = m B

!" Oscillatory Magnetic Field Angular displacement m : magnetic moment B : magnetic field ! : angle for magnetic field " : angle for magnetic moment ! : drag coefficient k : spring constant

From field, orientation data

  • – measure (viscosity) and k (elasticity)

Rotational drag Rotational elastic constant Torque

= mBsin( ) mB

How the disk responds

From field vs. orientation: recover ς(~viscosity) and κ (~elasticity)

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SLIDE 19

Surface drag of the probe

h D Total drag Bulk drag Bo = η(bulk viscosity)a ηs(surface viscosity)

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SLIDE 20

Apparatus

Allows interfacial visualization during measurement

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SLIDE 21

50 40 30 20 10 Surface Pressure / mN/m 120 100 80 60 40 Area/molecule / Å

2

DPPC and its isotherm

  • Major component of Lung surfactants and cell membranes
  • One of the most common phospholipids

(Equilibrium properties are well known)

high conc. low conc.

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SLIDE 22

50 40 30 20 10 Surface Pressure / mN/m 120 100 80 60 40 Area/molecule / Å

2

DPPC and its isotherm

  • Major component of Lung surfactants and cell membranes
  • One of the most common phospholipids

(Equilibrium properties are well known) Liquid Expanded(LE)

texas red DHPE(0.1mol%)

Inspired by Mcconnell

high conc. low conc.

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SLIDE 23

50 40 30 20 10 Surface Pressure / mN/m 120 100 80 60 40 Area/molecule / Å

2

DPPC and its isotherm

  • Major component of Lung surfactants and cell membranes
  • One of the most common phospholipids

(Equilibrium properties are well known) LC+LE coexistence Liquid Expanded(LE)

texas red DHPE(0.1mol%)

Inspired by Mcconnell

high conc. low conc.

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SLIDE 24

50 40 30 20 10 Surface Pressure / mN/m 120 100 80 60 40 Area/molecule / Å

2

DPPC and its isotherm

  • Major component of Lung surfactants and cell membranes
  • One of the most common phospholipids

(Equilibrium properties are well known) Liquid condensed(LC) LC+LE coexistence Liquid Expanded(LE)

texas red DHPE(0.1mol%)

Inspired by Mcconnell

high conc. low conc.

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SLIDE 25

Elasticity - domain deformation Viscosity - Slipping domains

Linear viscoelasticity of LC phase

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SLIDE 26

Elasticity - domain deformation Viscosity - Slipping domains

Slow dynamics

  • does not flow for 10 sec

Elastic dominant Viscous dominant

8 9

0.1

2 3 4

Surface Dynamic Modulus / uN /m

8

0.1

2 4 6 8

1

2 4 6 8

10

2

Frequency / Hz

G’ G’’

Linear viscoelasticity of LC phase

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SLIDE 27

Elasticity - domain deformation Viscosity - Slipping domains

Incredibly long relaxation time for 2 nm thick film Slow dynamics

  • does not flow for 10 sec

Elastic dominant Viscous dominant

8 9

0.1

2 3 4

Surface Dynamic Modulus / uN /m

8

0.1

2 4 6 8

1

2 4 6 8

10

2

Frequency / Hz

G’ G’’

Linear viscoelasticity of LC phase

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SLIDE 28

Elasticity - domain deformation Viscosity - Slipping domains

Incredibly long relaxation time for 2 nm thick film Slow dynamics

  • does not flow for 10 sec

Elastic dominant Viscous dominant

8 9

0.1

2 3 4

Surface Dynamic Modulus / uN /m

8

0.1

2 4 6 8

1

2 4 6 8

10

2

Frequency / Hz

G’ G’’

Linear viscoelasticity of LC phase

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SLIDE 29

Elasticity - domain deformation Viscosity - Slipping domains

Incredibly long relaxation time for 2 nm thick film Slow dynamics

  • does not flow for 10 sec

Elastic dominant Viscous dominant

8 9

0.1

2 3 4

Surface Dynamic Modulus / uN /m

8

0.1

2 4 6 8

1

2 4 6 8

10

2

Frequency / Hz

G’ G’’

Linear viscoelasticity of LC phase

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SLIDE 30

Where does this G’ come from?

G' ~ γ a a2 ~ γ a

γ ~ G'a ~ 10−7(N / m) ×10−5(m) ~ 1pN

From emulsion theory

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SLIDE 31

Where does this G’ come from?

G' ~ γ a a2 ~ γ a

γ ~ G'a ~ 10−7(N / m) ×10−5(m) ~ 1pN

line tension ~ adhesive energy length kT 1 nm ~ 1 pN ~ Molecular argument From emulsion theory

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SLIDE 32

Where does this G’ come from?

G' ~ γ a a2 ~ γ a

γ ~ G'a ~ 10−7(N / m) ×10−5(m) ~ 1pN

surface tension ~ adhesive energy area ~ kT 1 nm2~ 1 mN/m line tension ~ adhesive energy length kT 1 nm ~ 1 pN ~ Molecular argument From emulsion theory

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SLIDE 33

Linear rheology after large shear

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SLIDE 34

Linear rheology after large shear

Viscous dominant over frequencies

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SLIDE 35

Linear rheology after large shear

Viscous dominant over frequencies

History dependent rheology

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SLIDE 36

Visualization for large shear

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SLIDE 37
  • Domain deformation
  • Interface fractures(plastic)
  • Slip-line forms

Visualization for large shear

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SLIDE 38
  • Domain deformation
  • Interface fractures(plastic)
  • Slip-line forms

Visualization for large shear

Does the interface heal?

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SLIDE 39

Complete healing of the deformed domains

Before deforming

0 sec 30 sec 60 sec 0 sec 60 sec 30 sec

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SLIDE 40

Complete healing of the deformed domains

Before deforming

0 sec 30 sec 60 sec 0 sec 60 sec 30 sec

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SLIDE 41

Complete healing of the deformed domains

Before deforming

0 sec 30 sec 60 sec

20 times smaller moduli after large stress

0 sec 60 sec 30 sec

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SLIDE 42

Complete healing of the deformed domains

Before deforming

0 sec 30 sec 60 sec

20 times smaller moduli after large stress Viscous - Elastic transition

0 sec 60 sec 30 sec

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SLIDE 43

A few clues of yield stress

Elastic dominant Viscous dominant

8 9

0.1

2 3 4

Surface Dynamic Modulus / uN /m

8

0.1

2 4 6 8

1

2 4 6 8

10

2

Frequency / Hz

G’ G’’

3 4 5 6 7 8 9

0.1 Surface Dynamic Modulus / uN /m

3 4 5 6 7 8 9

0.1

2 3 4 5 6 7 8 9

Amplitude / rad

Point that starts to yield Frequency sweep Amplitude sweep

2 nm molecular Mayonnaise??

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SLIDE 44

Steady rotation - yield stress

No yield stress

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SLIDE 45

Steady rotation - yield stress

No yield stress

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SLIDE 46

Steady rotation - yield stress

No yield stress

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SLIDE 47

Steady rotation - yield stress

No yield stress

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SLIDE 48

Steady rotation - yield stress

higher stress

τ  σ yr

c(2πr c)

applied stress~ yield stress

  • Evident yield stress

σ y ~ 10−8 N / m

No yield stress

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SLIDE 49

Steady rotation - yield stress

higher stress

τ  σ yr

c(2πr c)

applied stress~ yield stress

  • Evident yield stress

σ y ~ 10−8 N / m

No yield stress

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SLIDE 50

Steady rotation - yield stress

higher stress

τ  σ yr

c(2πr c)

applied stress~ yield stress

  • Evident yield stress

σ y ~ 10−8 N / m

No yield stress

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SLIDE 51

Steady rotation - yield stress

higher stress

τ  σ yr

c(2πr c)

applied stress~ yield stress

  • Evident yield stress

σ y ~ 10−8 N / m

No yield stress

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SLIDE 52

Yield stress

Theories and experiments by Daniel Bonn

Thixotropic behavior

(time dependent viscosity)

Aging (system) vs Rejuvenation (applied stress)

Can we do analogous experiments after yielding the interface?

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SLIDE 53

After ~ 5 minutes rotation We turn off the field

25x real time

Healing by unwinding

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SLIDE 54

After ~ 5 minutes rotation We turn off the field

25x real time

Healing by unwinding

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SLIDE 55

After ~ 5 minutes rotation We turn off the field

25x real time

Field off

Healing by unwinding

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SLIDE 56

After ~ 5 minutes rotation We turn off the field

25x real time

Field off

Healing by unwinding

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SLIDE 57

After ~ 5 minutes rotation We turn off the field

25x real time

Field off

Healing by unwinding

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SLIDE 58

After ~ 5 minutes rotation We turn off the field

25x real time

Strong memory Slow recovery

Field off

Healing by unwinding

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SLIDE 59

Domains don’t melt - they stretch!

Red - recoiling Blue - T1 transition Green - change its neighbor

Watching individual domains

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SLIDE 60

Rayleigh - Plateau instability

3D

high P low P low P

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SLIDE 61

Rayleigh - Plateau instability

3D

high P low P low P high P low P high P

2D Always stable without fluctuation or defects

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SLIDE 62

Rayleigh - Plateau instability

No Rayleigh-Plateau instability for 2D 3D

high P low P low P high P low P high P

2D Always stable without fluctuation or defects

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SLIDE 63

Asymmetric stress response

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SLIDE 64

Chirality of DPPC

20 um 20 um

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SLIDE 65
  • Direct visualization of individual DPPC domains under stress
  • Shear banding, yield stress, history dependence and aging
  • 2D Soft glassy materials - 2D high internal phase emulsions

Conclusion