Department of Physics, Indian Institute of Science, Bangalore 560012, India.
Center for Computational Biology, Flatiron Institute, New York, NY 10010.
Proc Natl Acad Sci U S A. 2022 Aug 9;119(32):e2204453119. doi: 10.1073/pnas.2204453119. Epub 2022 Aug 1.
Changes in the geometry and topology of self-assembled membranes underlie diverse processes across cellular biology and engineering. Similar to lipid bilayers, monolayer colloidal membranes have in-plane fluid-like dynamics and out-of-plane bending elasticity. Their open edges and micrometer-length scale provide a tractable system to study the equilibrium energetics and dynamic pathways of membrane assembly and reconfiguration. Here, we find that doping colloidal membranes with short miscible rods transforms disk-shaped membranes into saddle-shaped surfaces with complex edge structures. The saddle-shaped membranes are well approximated by Enneper's minimal surfaces. Theoretical modeling demonstrates that their formation is driven by increasing the positive Gaussian modulus, which in turn, is controlled by the fraction of short rods. Further coalescence of saddle-shaped surfaces leads to diverse topologically distinct structures, including shapes similar to catenoids, trinoids, four-noids, and higher-order structures. At long timescales, we observe the formation of a system-spanning, sponge-like phase. The unique features of colloidal membranes reveal the topological transformations that accompany coalescence pathways in real time. We enhance the functionality of these membranes by making their shape responsive to external stimuli. Our results demonstrate a pathway toward control of thin elastic sheets' shape and topology-a pathway driven by the emergent elasticity induced by compositional heterogeneity.
自组装膜的几何形状和拓扑结构的变化是细胞生物学和工程学中多种过程的基础。类似于脂质双层，单层胶体膜具有面内流体动力学和面外弯曲弹性。它们的开口边缘和微米级长度尺度为研究膜组装和重构的平衡能学和动态途径提供了一个易于处理的系统。在这里，我们发现，用短的可混溶棒掺杂胶体膜会将盘状膜转变为具有复杂边缘结构的鞍状表面。鞍状膜可以很好地用 Enneper 的最小曲面来近似。理论模型表明，它们的形成是由正高斯模量的增加驱动的，而正高斯模量又由短棒的分数控制。进一步的鞍状表面的聚结导致了不同拓扑的不同结构，包括类似于 catenoid、trinoid、four-noid 和更高阶结构的形状。在长时间尺度上，我们观察到形成了一个跨越整个系统的海绵状相。胶体膜的独特特征揭示了伴随真实聚结途径的拓扑转变。我们通过使膜的形状对外界刺激做出响应来增强其功能。我们的结果表明了一种控制薄弹性片的形状和拓扑的途径——一种由组成异质性引起的新兴弹性驱动的途径。
