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Active microrheology and simultaneous visualization of sheared phospholipid monolayers.

Nature communications (2011-05-19)
S Q Choi, S Steltenkamp, J A Zasadzinski, T M Squires
ABSTRACT

Two-dimensional films of surface-active agents-from phospholipids and proteins to nanoparticles and colloids-stabilize fluid interfaces, which are essential to the science, technology and engineering of everyday life. The 2D nature of interfaces present unique challenges and opportunities: coupling between the 2D films and the bulk fluids complicates the measurement of surface dynamic properties, but allows the interfacial microstructure to be directly visualized during deformation. Here we present a novel technique that combines active microrheology with fluorescence microscopy to visualize fluid interfaces as they deform under applied stress, allowing structure and rheology to be correlated on the micron-scale in monolayer films. We show that even simple, single-component lipid monolayers can exhibit viscoelasticity, history dependence, a yield stress and hours-long time scales for elastic recoil and aging. Simultaneous visualization of the monolayer under stress shows that the rich dynamical response results from the cooperative dynamics and deformation of liquid-crystalline domains and their boundaries.

MATERIALS
Product Number
Brand
Product Description

Avanti
16:0 PC (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, powder
Avanti
16:0 PC (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, chloroform