Spreading of a liquid crystal droplet on a solid surface resembles the collapse of a zigguratlike structure and ends up with only two molecular terraces. A model is proposed to describe the time evolution of this late stage structure. It differs from the previous de Gennes-Cazabat theory by several aspects: (1) it avoids previous approximations and gives exact solutions of the kinetic equations; (2) it covers strongly layered liquids such as smectic liquid crystals; (3) it introduces the two-dimensional Laplace pressure as an essential motor for spreading; (4) it takes into account the liquid∕gas transition in the surface layer that was consistently reported in experiments with 8CB.

Using the surface enhanced ellipsometric contrast microscopy, we follow the last stage of the spreading of egg phosphatidylcholine nanodroplets on a hydrophilic substrate in a humid atmosphere, focusing on the vanishing trilayer in terraced droplets reduced to coexisting monolayer and trilayer. We find that the line interface between them exhibits two coexisting states, one mobile and one fixed. From there, it is possible to elucidate the internal structure and the spreading mechanism of the stratified liquid in a case of asymmetric wetting, i.e., where the lipid film is made of an odd number of leaflets.

The late stage kinetics of the spreading of a smectic nanodrop on a solid surface was investigated by direct and real time imaging of a three molecular layer patch using the SEEC microscopy. Experimental data do not conform to the only available theory, which covers only weakly stratified liquids. A new model is proposed, in remarkable agreement with experiments, in which the spreading mechanism appears to be a quasi-static process ruled by solid/liquid interactions, 2D Laplace pressure, and separate edge and surface permeation coefficients.

The last stage of the spreading of a stratified droplet in the odd wetting case is the evolution from a trilayer to a monolayer, that is, vanishing of the last bilayer in the stack. We studied it in the case of 8CB smectic liquid crystal on a hydrophilic surface. Receding of the last bilayer is accompanied by formation of pores in it, which appear in the outer part of it. From analysis of real-time experimental observations of this phenomenon, we demonstrate that the dislocation loops which border these pores are not located at the same height in the trilayer stack as the dislocation lines that border the bilayer. Also, careful analysis of our results using a recently developed theoretical approach of smectic liquid nanodrop spreading strongly suggests that pore nucleation is triggered by differences in chemical potential between adjacent layers, which contrasts with the classical scheme where it is attributed to lateral tension along the layers.

The spreading of a smectic nanodrop (8CB liquid crystal) on a solid surface was investigated by direct and real time imaging using the Surface Enhanced Ellipsometric Contrast (SEEC) microscopy [1-2]. The spreading ends with two molecular terraces (made of one monolayer and a bilayer). Two different behaviors were observed. In the first one the upper layer stays dense while shrinking. At the end of the process, the last molecules to disappear are located at the center of the initial disk. In the second one, nucleation and growth of holes is observed in the upper layer, in addition to shrinking. A model is proposed to describe the time evolution of the late stage structure. This model gives exact solutions of the kinetic equations, it covers strongly layered liquids such as smectic liquid crystals, it introduces the two dimensional Laplace pressure as an essential motor for spreading and it takes into account the liquid/gas transition in the surface layer that was consistently reported in experiments with 8CB. This model is in remarkable agreement with the experimental data and can explain the two observed behaviors [3].