Fluctuations and defects in quasi 2D smectic phases
We found a surface freezing transition in a mixture of colloidal liquid crystals and non-adsorbing
polymers. In the surface induced phase, smectic layers wet the isotropic-nematic interface with rods lying in the place of the
interface. Using optical microscopy we can directly visualize the quasi-2D smectic phase and quantify its fluctuations.
Surprisingly we find that by changing the conditions it is possible to continuously swell the surface induced smectic phase to the
point where individual smectic layers are observed.
Movie: 2D smectic with
splay. [MOV - 2mb]
Fluctuations of the surface induced smectic phase are shown in the above movie. A dense
nematic phase is below the image plane while a polymer rich isotropic phase is above the image plane. The thickness
of the surface-induced smectic phase is about 100 nm while the diameter of an individual fd rod is about 10 nm. There
is a strong coupling between the surface smectic layer and the background nematic phase which results in novel
An isotropic-nematic surface which is partially covered by smectic layers. A bacterium often gets
trapped at the interface and swims along the nematic director. The flagella of the bacterium can easily distort the
smectic layers as is visible in the movie. Alternatively it is possible to scan a laser tweezer along the interface and
create novel defects.
Movie: Bacteria on
surface. [MOV - 2mb]
[MOV - 2mb]
A low volume fraction of rods is fluorescently labeled and fluorescent image is overlaid over DIC
image. We hope to simultaneously study the dynamics of individual rods using fluorescence microscopy and long
wavelength fluctuations using DIC microscopy.