Metastability in pixelation patterns of coexisting fluid lipid bilayer phases imposed by e-beam patterned substrates.
Metastability in pixelation patterns of coexisting fluid lipid bilayer phases imposed by e-beam patterned substrates.
复制标题
电子束图案化基底施加的共存流体脂质双层相的像素化图案的亚稳定性。
DOI：
10.1039/c2sm27027g
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发表时间：
2013
期刊：
影响因子：
3.4
通讯作者：
Longo,MarjorieL
中科院分区：
文献类型：
--
作者：
Ogunyankin,MariaO;Longo,MarjorieL
我们研究了脂质多层中与液体无序相共存的液体有序（Lo）相的像素化模式的动态演化。像素化图案是通过使用底层支撑物的曲率图案区域在相分离多层上施加局部高曲率的晶格图案而形成的。使用标准电子束光刻技术，提供局部曲率的底层半球状特征的投影半径从 60 nm 变化到 100 nm，并且特征之间的方形晶格间距在 200 nm 到 400 nm 之间变化。随着时间的推移，室温下基板图案区域上 Lo 相的面积分数逐渐减小至零。图案的这种明显的亚稳定性源于像素化图案的高线能量，其中玻尔兹曼分布显示图案化区域中Lo相的接近零平衡分配。动力学速率分析确定了两种依赖于模式的机制，它们主导着向零 Lo 面积分数的转变；扩散限制了由奥斯特瓦尔德成熟型过程或含有 Lo 相脂质的囊泡的协同形成驱动的 Lo 相的溶解。有趣的是，我们观察到由于应用于膜的高局部曲率，在阵列的角落中自发形成小管。此外，我们表明可以通过冷却到室温以下来在曲率图案区域上重新生成像素化图案。再生面积分数与主要 Ld 相的室温组成一致，并且与原始图案的高度重叠表明固定的成核位点。
We study the dynamic evolution of pixilation patterns of the liquid-ordered (Lo) phase in coexistence with the liquid-disordered phase in lipid multibilayers. The pixilation patterns were formed by imposing lattice patterns of localized high curvature on phase-separating multibilayers using curvature-patterned regions of an underlying support. The projected radius of underlying hemisphere-like features, that provided the local curvature, was varied from 60 nm to 100 nm and the square lattice spacing between the features was varied between 200 nm and 400 nm using standard electron (e)-beam lithography. Over time, the area fraction of the Lo phase on the patterned regions of the substrate decreased toward zero at room temperature. This apparent metastability of the pattern derives from the high line energy of a pixelation pattern where a Boltzmann distribution shows near zero equilibrium partitioning of the Lo phase in the patterned regions. Kinetic rate analysis identifies two pattern-dependent mechanisms that dominate the transition to zero Lo area fraction; diffusion limited dissolution of the Lo phase driven by an Ostwald ripening-type process or the cooperative formation of vesicles containing Lo phase lipids. Interestingly, we observed the spontaneous formation of tubules in the corners of the array due to the high local curvature applied to the membrane. Furthermore we show that it is possible to regenerate pixilation patterns on the curvature-patterned regions by cooling below room temperature. Regenerated area fractions are in agreement with a room-temperature composition of primarily Ld phase and the high degree of overlap with the original patterns is suggestive of fixed nucleation sites.