Topological shape transitions of colloidal membranes

胶体膜的拓扑形状转变

• 批准号: 1905384
• 负责人: Zvonimir Dogic
• 金额: $ 56.13万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1905384&HistoricalAwards=false
• 关键词: Topological; shape; transitions; colloidal; membranes

Non-technical abstract:Elucidating the rules by which thin flat sheets fold into complex three dimensional structures is of fundamental interest to a broad range of fields ranging from physics, and materials science to biology. For example, the process by which a flat 2D bilayer with exposed edges folds into an edgeless 3D vesicle is essential for transport across cellular membranes and also for developing new methods of drug delivery. However, visualizing and quantifying such folding processes using nanometer-sized lipid bilayers is currently not feasible. This project will use an analogy between lipid bilayer and colloidal monolayer membranes to quantitatively test foundational models of vesicle formation and other folding processes. Colloidal membranes will allow one to measure all the parameters and directly visualize the folding process with optical microscopy, to a degree that is not possible with conventional materials. Besides visualizing closed vesicle formation the team will also study processes by which flat sheets fold into topologically more complex mathematical structures, such as catenoids and Gyroid-like structures. In parallel, the team will pursue outreach activities focused on (1) providing rigorous training in interdisciplinary sciences to graduate and undergraduate students, (2) encouraging underrepresented groups to pursue work in STEM related fields, (3) and raising general awareness of the importance of scientific research to broader communities. This project will actively support undergraduate research and will build on a strong record of recruiting students from diverse backgrounds. They will also continue their involvement with the Cal-Bridge program, a NSF-funded program whose mission is to increase the number of underrepresented minority and female students entering doctoral program in physics. Finally, each year they will also participate in about half a dozen outreach activities at local elementary and middle schools in order to promote science education.Technical abstract: Colloidal membranes, which are comprised of one-rod-length thick liquid-like monolayer of aligned monodisperse rods, offer a unique opportunity to explore fundamental aspect of thin sheets with vanishing in-plane shear modulus. So far, studies have mainly examined the behavior of colloidal membranes in the regime were they remain flat 2D structures. The goal of the current project is to elucidate the fundamental laws by which 2D colloidal membranes fold into diverse and topologically distinct 3D architectures. Three specific aims are proposed. In the first aim they will develop active and passive fluctuations-based techniques to measure the mean and Gaussian elastic moduli of colloidal membranes, the phenomenological constants that determine the energetic cost required to bend a membrane from its minimum energy state. In the second aim they will tune microscopic constituents of colloidal membranes to investigate regimes were flat colloidal membranes are inherently unstable and spontaneously fold into complex structures. In one direction they will reduce the bending rigidity of colloidal membranes to induce folding of flat 2D membranes into edgeless 3D vesicles and visualize and quantify the pathways of this transition. In a complementary direction they will explore the regime were doping colloidal membranes with miscible short rods induces formation of remarkably diverse and topological complex surfaces with negative Gaussian curvatures. Using state of the art imaging technique they will elucidate the molecular mechanisms that drive these instabilities. In the final aim they will develop robust experimental tools that will enable spatiotemporal external control of the membrane curvature, thus allowing one to actively intervene in the ongoing folding processes and guiding formation of topological assemblages of predetermined final shape.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要：阐明薄平板折叠成复杂三维结构的规则对从物理、材料科学到生物学的广泛领域都有根本意义。例如，边缘裸露的平面2D双层折叠成无边3D囊泡的过程对于跨细胞膜的运输和开发新的药物输送方法是必不可少的。然而，使用纳米尺寸的脂质双层来可视化和量化这种折叠过程目前是不可行的。该项目将使用脂质双层膜和胶体单层膜之间的类比来定量测试囊泡形成和其他折叠过程的基本模型。胶体膜将使人们能够测量所有参数，并用光学显微镜直接显示折叠过程，这是传统材料无法达到的程度。除了可视化闭合小泡的形成，研究小组还将研究平板折叠成拓扑上更复杂的数学结构的过程，如链状结构和类陀螺结构。同时，该小组将继续开展外联活动，重点是(1)为研究生和本科生提供跨学科的严格培训，(2)鼓励代表性不足的群体从事与STEM相关的领域的工作，(3)向更广泛的社区提高对科学研究重要性的普遍认识。该项目将积极支持本科生研究，并将建立在招收来自不同背景的学生的良好记录的基础上。他们还将继续参与加州桥项目，这是一个由NSF资助的项目，其使命是增加未被充分代表的少数族裔和女性学生进入物理学博士课程的数量。最后，他们每年还将在当地中小学参加大约六项外展活动，以促进科学教育。技术摘要：胶体膜由一棒长的厚液体状单分子层排列的单分散棒组成，为探索面内剪切模数为零的薄板的基本方面提供了一个独特的机会。到目前为止，研究主要考察了胶体膜在保持平面2D结构的情况下的行为。本项目的目标是阐明2D胶体膜折叠成各种不同的和拓扑上不同的3D结构的基本规律。提出了三个具体目标。在第一个目标中，他们将开发基于主动和被动涨落的技术来测量胶体膜的平均和高斯弹性系数，这些唯象常数决定了从最低能量状态弯曲薄膜所需的能量成本。在第二个目标中，他们将调整胶体膜的微观成分，以研究平坦的胶体膜天生不稳定并自发折叠成复杂结构的情况。在一个方向上，他们将降低胶体膜的弯曲刚性，诱导平坦的2D膜折叠成无边的3D囊泡，并可视化和量化这种转变的路径。在互补的方向上，他们将探索这样的制度，即掺杂带有可混溶短棒的胶体膜，诱导形成具有负高斯曲率的显着多样化和拓扑复杂的表面。利用最先进的成像技术，他们将阐明驱动这些不稳定性的分子机制。最终，他们将开发强大的实验工具，实现对膜曲率的时空外部控制，从而使人们能够积极干预正在进行的折叠过程，并指导预先确定的最终形状的拓扑组合的形成。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

All twist and no bend makes raft edges splay: Spontaneous curvature of domain edges in colloidal membranes

• DOI: 10.1126/sciadv.aba2331
• 发表时间: 2019-08
• 期刊: Science Advances
• 影响因子: 13.6
• 作者: Joia M. Miller;Douglas M Hall;Joanna Robaszewski;Prerna Sharma;M. Hagan;G. Grason;Z. Dogic