Wetting of bio-inspired, stimulus-responsive polymer surfaces by lipid vesicles

类似于液滴，囊泡的形状由其封闭体积、膜-基底相互作用（界面电位）以及内部和外部之间的界面（膜）的性质决定。囊泡润湿的独特之处在于膜固有的弯曲刚度和封闭液体的浮力。实验Tanaka团队建立了一个生物启发的聚合物刷平台，能够切换囊泡的粘附，并通过3D共聚焦显微镜监测大规模囊泡形状。这种设置将由显微干涉技术补充，提供有关刷囊接触区边缘的局部几何形状的信息。Müller团队在并行GPU加速的MD程序中实现了可切换聚合物刷的高度粗粒度粒子模型和薄脂质膜的三角化Helfrich-Hamiltonian，并将Helfrich描述推广到包括有限范围的界面势和浮力。在新的时期，他们将明确包括溶剂来解释粘性dissipation. Two团队将共同调查的动态变化的囊泡形状响应于开关的粘附和适应刷接触囊泡的囊泡几何形状的随时间变化的测量。热力学力（弯曲能、附着力和浮力）和耗散机制（例如，在接触区和周围液体的耗散）表现出对囊泡尺寸的不同依赖性，其系统变化将允许我们区分不同的耗散机制，并有助于实验和模拟之间的比较。此外，我们将考虑如何运输膜物种（例如，带正电荷的脂质，结合到刷的-COOH基团）朝向接触区影响囊泡的动力学。这条线的研究将扩展到异质基板，其中的润湿性梯度可能会导致在接触区的钉扎或逐渐变化可能会导致翻译和传播的囊泡。我们还将研究时间周期性开关的润湿性和润湿性梯度，在基板上移动。囊泡的横向运动将产生额外的动力学，例如囊泡的滑动或滚动运动/坦克踩踏。

Analog to liquid drops, the shape of a vesicle is dictated by its enclosed volume, the membrane-substrate interaction (interface potential), and the properties of the interface (membrane) between the interior and exterior. Unique to wetting by vesicles is the importance of the membrane’s intrinsic bending rigidity and the buoyancy of the enclosed liquid.The experimental Tanaka team has established a bio-inspired polymer brush platform, capable of switching the adhesion of vesicles, and has monitored the large-scale vesicle shape by 3D confocal microscopy. This setup will be complemented by a micro-interferometry technique, providing information about the local geometry of the edge of the brush-vesicle contact zone. The theoretical Müller team has implemented a highly coarse-grained particle model of the switchable polymer brush and a triangulated Helfrich-Hamiltonian of the thin lipid membrane in a parallel, GPU-accelerated MD program and has generalized the Helfrich description to include a finite-ranged interface potential and buoyancy. In the new period, they will explicitly include solvents to account for viscous dissipation.Both teams will jointly investigate the dynamic change of vesicle shapes in response to a switch in adhesion and the adaptation of the brush to the contact with a vesicle by time-dependent measurements of the vesicle geometry. Thermodynamic forces (bending energy, adhesion, and buoyancy) and dissipation mechanisms (e.g., dissipation at the contact zone and of the surrounding liquids) exhibit different dependencies on the vesicle size, whose systematic variation will allow us to distinguish between different dissipation mechanisms and aid the comparison between experiment and simulation. Additionally, we will consider how transport of membrane species (e.g., positively charged lipids, binding to -COOH groups of the brush) toward the contact zone influences the dynamics of the vesicle. This line of study will be extended to heterogeneous substrates, where a wettability gradient may result in a pining of the contact zone or a gradual variation may induce a translation and spreading of the vesicle. We will also study time-periodic switches of the wettability and wettability gradients that move over the substrate. The lateral motion of vesicles will give rise to additional dynamics such as e.g. sliding or rolling motion/tank-treading of the vesicle.