Hierarchical Assembly and Dynamic Transitions of DNA-Coated Colloids

非技术摘要胶体--分散在流体中的微观物质--是研究凝聚态物理现象的强大模型系统，也是有希望的纳米材料的构建块。像原子一样，它们形成物质的体相，如气体和晶体。但与原子不同的是，胶体粒子可以用信息编码，这些信息可以用来告诉它们如何组装成有用的结构。该项目的最终目标是通过将存储在粒子中的信息与出现的组装途径和复杂结构相关联，来改进指导或编程胶体自组装的方法。研究小组使用嫁接到胶体颗粒上的DNA序列，以及溶解在溶液中的其他DNA序列，来控制颗粒之间的相互作用，并研究这些颗粒如何组装形成各种结构。这些结果可能在纳米技术中特别有用，其中一个中心目标是通过直接从溶液中生长来制造材料和设备。该研究在新兴的跨学科领域可编程自组装中培养博士生和本科生，每年通过引人入胜的开放式实验室教育大约120名生命科学本科生，专注于将入门物理概念应用于生物学问题。技术摘要DNA涂层胶体可以组装成有趣的结构和相，是研究软凝聚态相变和自组装最有前途的实验系统之一。该实验项目研究并推进了一个未充分探索的范例，其中胶体通过溶液中的游离DNA链而不是接枝链的直接结合进行相互作用，并阐明了在这种系统中控制组装的基本规则。主要研究者的研究团队采用分层方法，定量研究从分子尺度到胶体尺度相互作用的整个信息流，然后从胶体相互作用到系统尺度上出现的相行为。正在解决的中心问题是：如何紧急阶段的行为取决于对相互作用的细节，以及如何对相互作用反过来又取决于溶解在溶液中的DNA链的属性？为了回答这些问题，研究小组使用了各种现代光学技术，包括光学显微镜，全内反射显微镜和微分动态显微镜，并开发了定量模型来解释和统一他们的观察结果。了解DNA序列如何被编译成结构和功能，对于自下而上的工程和制造材料的最终目标至关重要。该项目将培养软物质物理学和应用光学方面的博士生和本科生，并通过一系列使用光学显微镜的基于探究的实验室来教育生命科学方面的本科生。

NONTECHNICAL ABSTRACTColloids--microscopic bits of matter dispersed in a fluid--are powerful model systems for studying phenomena in condensed matter physics, as well as promising building blocks for nanomaterials. Like atoms, they form bulk phases of matter such as gases and crystals. But unlike atoms, colloidal particles can be encoded with information that can be used to tell them how to assemble into useful structures. The ultimate goal of this project is to improve methods for directing, or programming, colloidal self-assembly by relating the information stored in particles to the assembly pathways and complex structures that emerge. The research team uses DNA sequences grafted to colloidal particles, together with other DNA sequences dissolved in solution, to control interactions between particles, and investigates how these particles assemble to form various structures. The results could prove especially useful in nanotechnology, where a central goal is to manufacture materials and devices by growing them directly from solution. The research trains doctoral and undergraduate students in the emerging, interdisciplinary field of programmable self-assembly, and educates roughly 120 undergraduate students in the life sciences per year through engaging, open-ended labs focused on applying introductory physics concepts to problems in biology.TECHNICAL ABSTRACTDNA-coated colloids can assemble into interesting structures and phases, and are one of the most promising experimental systems for studying phase transitions and self-assembly in soft condensed matter. This experimental project investigates and advances an underexplored paradigm, in which colloids interact by free DNA strands in solution instead of direct binding of grafted strands, and elucidates the fundamental rules governing assembly in such systems. The principle investigator's research team takes a hierarchical approach, studying quantitatively the entire flow of information from the molecular scale to interactions at the colloidal scale, and then from the colloidal interactions to the phase behavior that emerges at the system scale. The central questions being addressed are: how does the emergent phase behavior depend on details of the pair interaction, and how does the pair interaction in turn depend on the attributes of DNA strands dissolved in solution? To answer these questions, the research team uses a variety of modern optical techniques, including optical microscopy, total internal reflection microscopy, and differential dynamic microscopy, and develops quantitative models to interpret and unite their observations. Understanding how DNA sequences are compiled into structure and function is essential to the ultimate goals of engineering and manufacturing materials from the bottom up. The project will train doctoral and undergraduate students in soft matter physics and applied optics, and educate undergraduates in the life sciences through a series of inquiry-based labs using optical microscopy.