Interfacial microrheology of phospholipid monolayers at the - PowerPoint PPT Presentation

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 Foams Shampoo, detergents, etc. Coating Process Lung surfactants High Internal Phase Emulsion(PS-P2VP) � Zasadzinski group (2003) � Kramer group (2003) �

Interfacial viscoelasticity A magnetic needle at the air/water Interface

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

Systems we are working on DPPC DPPC +Chol Colloidal crystal (phospholipid) (60:40) at the oil/water interface

Systems we are working on DPPC DPPC +Chol Colloidal crystal (phospholipid) (60:40) at the oil/water interface

Systems we are working on DPPC DPPC +Chol Colloidal crystal (phospholipid) (60:40) at the oil/water interface

Systems we are working on DPPC DPPC +Chol Colloidal crystal (phospholipid) (60:40) at the oil/water interface

Viscometry of 2D interfaces � s � : surface viscosity � � : subphase viscosity a : disk radius a � � s � P : Contact perimeter to 2D surface � � A : Contact Area to bulk phase “Boussinesq � Number” High perimeter/area ratio: higher sensitivity � High aspect ratio (e.g. needles – Brooks, Fuller, Vermant, Fischer, Zasadzinski …) � High aspect ratio (e.g. needles - Brooks, Fuller, Vermant, Fischer, Zasadzinski, ...) Small probes (microrheology – Sickert & Rondelez, Fischer, Dai, Weeks, …) � Small probes (microrheology - Weeks, Sickert & Rondelez, Fischer, Dai, ...

General Experimental Procedure Angular strain(t) � Image analysis Camera (Red) microscope electromagnets interface � Applied Torque ~ Stress � Rotational displacement ~ Strain subphase � Magnetic torque(t) � DATA acquisition board (Green) Imposed oscillatory Can compute magnetic field viscoelasticity(G’, G’’)

General Experimental Procedure Angular strain(t) � Image analysis Camera (Red) microscope electromagnets interface � Applied Torque ~ Stress � Rotational displacement ~ Strain subphase � Magnetic torque(t) � DATA acquisition board (Green) Can measure Imposed oscillatory Imposed constant Can compute Creep compliance--J(t) magnetic field stress viscoelasticity(G’, G’’)

Janus ferromagnetic microprobes

Janus ferromagnetic microprobes requirements • Small, yet visible • Ferromagnetic • Amphiphilic

Janus ferromagnetic microprobes Photolithography requirements • Small, yet visible • Ferromagnetic • Amphiphilic

Janus ferromagnetic microprobes Photolithography requirements • Small, yet visible • Ferromagnetic • Amphiphilic Thiol monolayer Au (~10 nm) Ni/Co (~100 nm) Photoresist (~ 1 um)

Janus ferromagnetic microprobes Photolithography requirements • Small, yet visible • Ferromagnetic • Amphiphilic Thiol monolayer 20 μ m diameter 1 μ m tall Au (~10 nm) Ni/Co (~100 nm) Photoresist (~ 1 um) 20 µ m bright field image Amphiphilic - Janus

Janus ferromagnetic microprobes Photolithography requirements • Small, yet visible • Ferromagnetic • Amphiphilic Thiol monolayer 20 μ m diameter 1 μ m tall Au (~10 nm) Ni/Co (~100 nm) Photoresist (~ 1 um) Control over Size, Shape, 20 µ m Magnetic and Surface bright field image Amphiphilic - Janus properties

How the disk responds I �� � + � � � + k � = m � B Rotational drag Rotational � Torque elastic constant = mB sin( � � � ) !" � mB m : magnetic moment � B : magnetic field � ! : angle for magnetic field � Oscillatory Magnetic Field � " : angle for magnetic moment � Angular displacement � ! : drag coefficient � k : spring constant � From field, orientation data � From field vs. orientation: – measure � (viscosity) and k (elasticity) � � � recover ς (~viscosity) and κ (~elasticity)

Surface drag of the probe Total drag Bulk drag D h η s(surface viscosity) Bo = η (bulk viscosity)a

Apparatus Allows interfacial visualization during measurement

DPPC and its isotherm 50 • Major component of Lung surfactants and cell membranes • One of the most common phospholipids (Equilibrium properties are well known) 40 Surface Pressure / mN/m 30 20 10 0 40 60 80 100 120 2 low conc. high conc. Area/molecule / Å

DPPC and its isotherm 50 • Major component of Lung surfactants and cell membranes • One of the most common phospholipids (Equilibrium properties are well known) 40 Surface Pressure / mN/m Inspired by Mcconnell texas red DHPE(0.1mol%) 30 20 10 Liquid Expanded(LE) 0 40 60 80 100 120 2 low conc. high conc. Area/molecule / Å

DPPC and its isotherm 50 • Major component of Lung surfactants and cell membranes • One of the most common phospholipids (Equilibrium properties are well known) 40 Surface Pressure / mN/m Inspired by Mcconnell texas red DHPE(0.1mol%) 30 20 LC+LE coexistence 10 Liquid Expanded(LE) 0 40 60 80 100 120 2 low conc. high conc. Area/molecule / Å

DPPC and its isotherm 50 • Major component of Lung surfactants and cell membranes • One of the most common phospholipids (Equilibrium properties are well known) 40 Surface Pressure / mN/m Inspired by Mcconnell texas red DHPE(0.1mol%) 30 20 LC+LE coexistence Liquid condensed(LC) 10 Liquid Expanded(LE) 0 40 60 80 100 120 2 low conc. high conc. Area/molecule / Å

Linear viscoelasticity of LC phase Elasticity - domain deformation Viscosity - Slipping domains

Linear viscoelasticity of LC phase 4 Surface Dynamic Modulus / uN /m Viscous dominant 3 G’ 2 Elastic dominant G’’ 0.1 9 8 8 2 4 6 8 2 4 6 8 2 0.1 1 10 Frequency / Hz Slow dynamics Elasticity - domain deformation - does not flow for 10 sec Viscosity - Slipping domains

Linear viscoelasticity of LC phase 4 Surface Dynamic Modulus / uN /m Viscous dominant 3 G’ 2 Elastic dominant G’’ 0.1 9 8 8 2 4 6 8 2 4 6 8 2 0.1 1 10 Frequency / Hz Slow dynamics Elasticity - domain deformation - does not flow for 10 sec Viscosity - Slipping domains Incredibly long relaxation time for 2 nm thick film

Linear viscoelasticity of LC phase 4 Surface Dynamic Modulus / uN /m Viscous dominant 3 G’ 2 Elastic dominant G’’ 0.1 9 8 8 2 4 6 8 2 4 6 8 2 0.1 1 10 Frequency / Hz Slow dynamics Elasticity - domain deformation - does not flow for 10 sec Viscosity - Slipping domains Incredibly long relaxation time for 2 nm thick film

Linear viscoelasticity of LC phase 4 Surface Dynamic Modulus / uN /m Viscous dominant 3 G’ 2 Elastic dominant G’’ 0.1 9 8 8 2 4 6 8 2 4 6 8 2 0.1 1 10 Frequency / Hz Slow dynamics Elasticity - domain deformation - does not flow for 10 sec Viscosity - Slipping domains Incredibly long relaxation time for 2 nm thick film

Where does this G’ come from? G ' ~ γ a a 2 ~ γ From emulsion theory a γ ~ G ' a ~ 10 − 7 ( N / m ) × 10 − 5 ( m ) ~ 1 pN

Where does this G’ come from? G ' ~ γ a a 2 ~ γ From emulsion theory a γ ~ G ' a ~ 10 − 7 ( N / m ) × 10 − 5 ( m ) ~ 1 pN Molecular argument kT adhesive energy line tension ~ ~ 1 pN ~ length 1 nm

Where does this G’ come from? G ' ~ γ a a 2 ~ γ From emulsion theory a γ ~ G ' a ~ 10 − 7 ( N / m ) × 10 − 5 ( m ) ~ 1 pN Molecular argument kT adhesive energy line tension ~ ~ 1 pN ~ length 1 nm kT adhesive energy 1 nm 2 ~ 1 mN/m surface tension ~ ~ area

Linear rheology after large shear

Linear rheology after large shear Viscous dominant over frequencies

Linear rheology after large shear Viscous dominant over frequencies History dependent rheology

Visualization for large shear

Visualization for large shear • Domain deformation • Interface fractures(plastic) • Slip-line forms

Visualization for large shear Does the interface heal? • Domain deformation • Interface fractures(plastic) • Slip-line forms

Complete healing of the deformed domains 0 sec 0 sec Before deforming 30 sec 30 sec 60 sec 60 sec

Complete healing of the deformed domains 0 sec 0 sec Before deforming 30 sec 30 sec 60 sec 60 sec

Complete healing of the deformed domains 0 sec 0 sec Before deforming 30 sec 30 sec 60 sec 60 sec 20 times smaller moduli after large stress

Complete healing of the deformed domains 0 sec 0 sec Before deforming 30 sec 30 sec 60 sec 60 sec 20 times smaller moduli after large stress Viscous - Elastic transition

A few clues of yield stress 2 nm molecular Mayonnaise?? Frequency sweep Amplitude sweep 4 Surface Dynamic Modulus / uN /m Surface Dynamic Modulus / uN /m Point that starts to yield Viscous dominant 0.1 3 9 8 G’ 7 2 6 5 Elastic dominant 4 G’’ 0.1 9 3 8 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 8 2 4 6 8 2 4 6 8 2 0.1 0.1 1 10 Amplitude / rad Frequency / Hz

Steady rotation - yield stress No yield stress

Steady rotation - yield stress No yield stress

Steady rotation - yield stress No yield stress

Steady rotation - yield stress No yield stress