Experimental observations of dynamic critical phenomena in a lipid membrane

TL;DR

This study investigates the critical dynamics of a lipid membrane near a phase transition, demonstrating that its fluctuation behavior aligns with theoretical predictions for 2D conserved order parameter systems, showing a crossover in dynamic exponent.

Contribution

First experimental verification of dynamic critical phenomena in a 2D lipid membrane with conserved order parameter, confirming theoretical universality class predictions.

Findings

Dynamic exponent $z_{eff}$ crosses from ~2 to ~3 as correlation length increases.

Critical dynamics in lipid membranes match 2D universality class predictions.

Fluctuation time scales diverge near the critical point as expected.

Abstract

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.