We present the first systematic measurement of critical dynamics of a 2D liquid with conserved order parameter embedded in bulk 3D fluid, here a lipid membrane in water . We use scaling to collapse time dependent structure factors at multiple wavenumbers and find the effective dynamic exponent z_{ eff } \approx 3 near the critical point. This value and the form of the structure factor are in excellent agreement with recent theoretical predictions invoking hydrodynamic coupling to the bulk. Our result may have biological relevance since membranes isolated from cells are near miscibility critical points .
Near a critical point, the time scale of thermally-induced fluctuations diverges in a manner determined by the dynamic universality class. Experiments have verified predicted 3D dynamic critical exponents in many systems, but similar experiments in 2D have been lacking for the case of conserved order parameter . Here we analyze time-dependent correlation functions of a quasi-2D lipid bilayer in water to show that its critical dynamics agree with a recently predicted universality class. In particular, the effective dynamic exponent z_{ \text{eff } crosses over from \sim 2 to \sim 3 as the correlation length of fluctuations exceeds a hydrodynamic length set by the membrane and bulk viscosities .
R
We present the first systematic measurement of critical dynamics of a
Near a critical point, the time scale of thermally-induced fluctuations diverges in a manner determined by the dynamic universality class. Experiments have verified predicted 3D dynamic critical exponents in many systems, but similar experiments in
R
liquid with
have been lacking for the case of
R
embedded in bulk 3D fluid, here a lipid membrane in water . We use scaling to collapse time dependent structure factors at multiple wavenumbers and find
. Here we analyze time-dependent correlation functions of a quasi-2D lipid bilayer in water to show that its critical dynamics agree with a recently predicted universality class. In particular,
R
eff
\text{eff
R
\approx
crosses over from \sim 2 to \sim
R
near the critical point. This value and the form of the structure factor are in excellent agreement with recent theoretical predictions invoking hydrodynamic coupling to the bulk. Our result may have biological relevance since membranes isolated from cells are near miscibility critical points
as the correlation length of fluctuations exceeds a hydrodynamic length set by the membrane and bulk viscosities