CAREER: Designing Colloidal Materials By Tilting the Free Energy Surface

该职业奖支持理论和计算研究和教育，以促进对自组装的基本理解，并研究如何控制过程以获得所需的材料和分子结构。在我们周围的世界里，自组装随处可见，它是一种表面上杂乱无章的现有组件，随着时间的推移而形成高度有组织的结构。许多自然系统利用少量的相互作用作为规则，诱导无限范围的分子成分形成定义良好的结构。这些在生物系统中最为明显，在那里，复杂而坚固的组装允许生命的微妙之舞。长期以来，研究人员一直试图在实验室合成中复制这些行为，创造出能够自组装成具有有利机械、光学或电学性能的材料的设计分子和粒子。这些努力取得了不同程度的成功。虽然使用与生物学相似的调色板，但设计的系统往往达不到生物学的精度，导致材料的无序聚集而不是期望的排列。胶体材料是由物质的一个阶段的小块分散到另一个阶段而产生的，是研究自组装过程和机制的理想场所。特别是固体胶体粒子，它可以被设计成模拟分子间的相互作用。由于布朗运动和重排在显微镜下很容易观察到，因此在组装过程中有序结构的演变可以很容易地通过实验跟踪和潜在地控制。该职业奖支持使用强大的计算模型来开发胶体材料可能聚集成的团簇的全面图像，以及如何通过修改胶体颗粒的结构和组成来实现特定的聚集体。这项工作将直接用于合成具有特定相互作用的新胶体，目标是强大的簇组装和分阶段组装过程，以创建复杂的有序结构。该项目的综合外展和教育部分遵循课堂参与、公众外展和研究指导的三重方法。主要工作是扩大PI与印第安纳州南本德公立学校发起的课堂推广计划，以研究烹饪科学，特别是日常食物的质地、成分、味道和视觉吸引力是如何从分子水平相互作用的熟练操作中产生的。最初的课堂演示将扩展为一套针对印第安纳州高中物理科学和科学素养标准的可食用实验室活动。此外，这项工作将支持有才华的年轻本科生参与计算材料研究，并将分子组装和相关概念纳入本科热力学课程。该职业奖支持理论和计算研究和教育，以促进对自组装的基本理解，并研究如何控制过程以获得所需的材料和分子结构。自组装在生物系统中无处不在，复杂而坚固的形成结构激发了科学家和工程师在实验室中模拟自然世界。许多成功的方法直接来源于生物学，通过模拟潜在的化学或直接利用生物分子来促进特定的相互作用。尽管生物世界和合成世界的组装规则可能是相似的，但对设计自组装的短短几十年的研究尚未达到在生物领域观察到的优化合成过程的程度。因此，许多尝试导致了部分有序的系统，充满了意想不到的组装，而不是严格选择所需结构的形成。胶体材料是研究自组装过程和机制的理想场所，由于高度可调的粒子-粒子相互作用。此外，在显微镜下很容易观察到胶体聚集体的布朗运动和结构重排。因此，快速形成的团簇可以通过它们的成核、生长和重新排列，从局部首选构型走向全局热力学最小值。在过去的几十年里，胶体的研究有了很大的增加，重点是合成能够自组装成定义结构的新粒子，特别是具有理想光子特性的开放晶体结构。尽管如此，许多新的组装方法在创建真正可调的开放结构方面收效甚微，因为它们主要关注最小化粒子间能量，并且可能包含许多导致错误组装的特征。该职业奖支持利用强大的平面直方图和反应途径采样算法来获得控制胶体组装的稳定和亚稳的自由能表面盆地，以及这些状态之间的过渡途径的工作。这些信息形成了胶体团簇自组装的全面图景，并直接指导新胶体的实验合成，这些胶体通过特定的相互作用倾斜自由能表面，针对健壮的团簇组装和分阶段组装过程，以创建定制的开放胶体晶格。该提案中的综合研究和教育计划遵循课堂参与、公众宣传和研究指导的三重方法。主要的努力涉及扩大PI与印第安纳州南本德公立学校发起的课堂推广计划，以检查烹饪科学。这些活动展示了日常食物的质地、成分、味道和视觉吸引力是如何来自于分子水平相互作用的熟练操作。该项目将把最初的课堂演示扩展到互动和可食用的实验室调查，目标是印第安纳州高中的物理科学和科学素养标准。这项工作还将支持有才华的本科生参与计算材料研究，并将分子组装和相关概念纳入本科热力学课程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYThis CAREER award supports theoretical and computational research and education to advance fundamental understanding of self-assembly and investigate how to control the process to achieve desired materials and molecular structures. Self-assembly, where an apparently disordered array of existing components results over time in highly organized structures, is everywhere in the world around us. Many natural systems utilize a small palette of interactions as rules to coax the limitless range of molecular components into well-defined structures. These are most evident in biological systems, where intricate yet robust assemblies permit the delicate dance of life. Researchers have long sought to replicate these behaviors in laboratory syntheses, creating designer molecules and particles which self-assemble into materials with advantageous mechanical, optical, or electrical properties. These efforts have met varying degrees of success. Though working with a similar palette to biology, designed systems often fall short of biological precision, resulting in disordered aggregates of material rather than the desired arrangements.Colloidal materials, created by the dispersion of small pieces of one phase of matter into another, are ideal places to study the processes and mechanisms of self-assembly. Particularly, this is true for solid colloidal particles which may be designed to mimic the interactions of molecules. As the Brownian motion and rearrangements are readily observable under a microscope, the evolution of ordered structures during assembly may be easily tracked experimentally and potentially controlled. This CAREER award supports the use of powerful computational modeling to develop a comprehensive picture of the clusters colloidal materials are likely to assemble into, and how specific aggregates may be achieved by modifying the structure and composition of colloidal particles. The work will be used to directly inform the synthesis of new colloids with specific interactions, targeting robust cluster assemblies and staged assembly processes to create complex ordered structures.Integrated outreach and education components within this program follow a threefold approach of classroom engagement, public outreach, and research mentoring. The primary effort is the expansion of a classroom outreach program the PI has initiated with South Bend, Indiana public schools to examine the science of cooking, and in particular how the texture, composition, flavor and visual appeal of everyday foods derive from skillful manipulation of molecular-level interactions. Initial classroom demonstrations are to be expanded into a set of edible laboratory activities targeting Indiana high school physical science and scientific literacy standards. Also, this work will support the involvement of talented young undergraduates in computational materials research and the incorporation of molecular assembly and related concepts into the undergraduate thermodynamics curriculum.TECHNICAL SUMMARYThis CAREER award supports theoretical and computational research and education to advance fundamental understanding of self-assembly and investigate how to control the process to achieve desired materials and molecular structures. Self-assembly is ubiquitous in biological systems, and the intricate yet robustly forming structures there inspire scientists and engineers to mimic the natural world within the laboratory. Many successful approaches have derived directly from biology, by simulating the underlying chemistry or directly utilizing biomolecules to promote specific interactions. Though the rules of assembly in the biological and synthetic worlds may be similar, the mere decades of research into designed self-assembly have yet to optimize synthetic processes to the degree observed in the biological realm. Thus, many attempts result in partially ordered systems full of unintended assemblies rather than strict selective formation of the desired structures.Colloidal materials are ideal places to study the processes and mechanisms of self-assembly, due to highly tunable particle-particle interactions. Additionally, the Brownian motion and structural rearrangements of colloidal aggregates are readily observed under a microscope. Therefore, clusters which quickly form can be followed through their nucleation, growth, and rearrangement from locally preferred configurations toward a global thermodynamic minimum. Over the past few decades, there has been a great increase in colloidal research focusing on synthesis of novel particles which can self-assemble into defined structures, and in particular open crystalline structures which have desirable photonic properties. Even so, many of these new assembly methods have seen little success in creating truly tunable open structures as they focus largely on minimizing inter-particle energies and can contain many features leading to mis-assembly. This CAREER award supports work utilizing powerful flat histogram and reactive pathway sampling algorithms to obtain stable and metastable basins of the free energy surface controlling colloidal assembly, as well as transition pathways between these states. This information forms a comprehensive picture of the self-assembly of colloidal cluster, and directly informs the experimental syntheses of new colloids which tilt the free energy surface through specific interactions, targeting robust cluster assemblies and staged assembly processes to create bespoke open colloidal lattices.Integrated research and education plans within this proposal follow a threefold approach of classroom engagement, public outreach, and research mentoring. The primary effort concerns the expansion of a classroom outreach program the PI has initiated with South Bend, Indiana public schools to examine the science of cooking. These activities demonstrate how the texture, composition, flavor and visual appeal of everyday foods derive from skillful manipulation of molecular-level interactions. The PI will extend initial classroom demonstrations into interactive and edible lab investigations targeting Indiana high school physical science and scientific literacy standards. This work will also support the involvement of talented undergraduates in computational materials research and the incorporation of molecular assembly and related concepts into the undergraduate thermodynamics curriculum.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.