NIRT: Directed Assembly of Nanostructures: Theory, Simulations, and Experiments in Hard and Soft Materials

该提案是响应纳米科学与工程倡议，NSF 03-043，类别NIRT。 定向自组装和聚集为制造纳米级结构提供了巨大的可能性。挑战在于要求将原子、分子或粒子组装成复杂且高度有序的纳米级结构。这种结构的潜在应用出现在广泛的技术中，包括纳米和分子电子学、用于数据存储的高密度图案化介质、光电子学和纳米传感器阵列等。 使用外部施加的场来控制和指导微米和纳米结构的演变是实现这种精确控制聚集的非常有前途的途径。外场与物质相互作用以产生纳米级有序聚集体的实际应用将需要基本的理解和工程设计方法。虽然许多新的相行为在微米级和纳米级系统的最初发现已经出现从纯粹的实验研究，它是越来越明显的是，建模和预测微观结构的演变能力将是至关重要的实现有效和实用的控制在纳米级。 拟议的研究旨在通过大量的建模和理论工作，结合硬材料和软材料系统中最先进的实验来实现这一目标，每个系统都具有互补的优势。硬（或原子）系统，例如晶体材料中的纳米沉淀物，很难在实验上或理论上完全表征。另一方面，胶体或软系统在设置控制粒子-粒子相互作用的“微观”性质和进行直接实验观察的能力方面提供了更大的灵活性，特别是在依赖于时间的现象的情况下。这项研究的结果将是一个物理为基础的框架，实现定向聚合在硬和软系统。在这两种情况下，统一的主题将是通过外部施加的场来诱导和控制运输。例子包括硬材料中的应力，软材料中的熵场，以及两者中的化学势。 场辅助定向组装的概念不是材料特定的，并且所提出的研究将作为在非常广泛的材料中定向纳米级聚集的建模和实验设计的一般基础。它可能会提供全新的见解聚集的机制，并揭示方面是共同的，几乎所有的材料。 与此同时，通过利用共同的基本特征，加深了解将有助于在不同的技术应用之间转让方法。 这种统一的概念是至关重要的，因为高科技材料变得越来越复杂，表面上无关。 最后，本研究对研究生教育的影响是深远的。越来越明显的是，需要新一代的科学家和工程师来领导纳米技术的发展，这需要化学工程，材料科学和材料力学的综合培训。这个紧密结合的项目将为这种跨学科培训提供一个理想的框架。该研究由化学和运输系统部门的热运输和热处理计划，化学和运输系统部门的界面，运输和热力学计划，土木和机械系统部门的材料力学和结构计划以及设计，制造和工业创新部门的纳米制造计划共同资助。

This proposal was received in response to Nanoscale Science and Engineering initiative, NSF 03-043, category NIRT. Directed self-assembly and aggregation offers tremendous possibilities for making structures at the nanoscale. The challenge lies in the requirement that atoms, molecules, or particles be assembled into complex and highly organized nanometer-sized structures across centimeters. Potential applications for such structures arise in a wide range of technologies, including nano and molecular electronics, high-density patterned media for data storage, optoelectronics, and nanosensor arrays to name a few. The use of externally applied fields to control and direct micro- and nanostructural evolution is a very promising avenue for achieving such precise control of aggregation. The practical application of external-field interactions with matter to create nanoscale, ordered aggregates will require both fundamental understanding and engineering design methodologies. While many of the initial discoveries of novel phase behavior in microscale and nanoscale systems have arisen from purely experimental investigations, it is increasingly apparent that the ability to model and predict microstructural evolution will be of central importance for achieving effective and practical control at the nanoscale. The proposed research aims to accomplish this goal with a substantial modeling and theoretical effort in conjunction with state-of-the-art experiments in both hard and soft material systems, each of which offers complementary advantages. Hard (or atomic) systems, e.g. nanoprecipitates in crystalline materials, are very difficult to completely characterize either experimentally or theoretically. Colloidal or soft systems, on the other hand, offer greater flexibility both in setting the "microscopic" properties that control particle-particle interactions and in the ability to make direct experimental observations, particularly in the case of time-dependent phenomena. The outcome of this research will be a physically based framework for achieving directed aggregation in both hard and soft systems. In both cases, the unifying theme will be the induction and control of transport by externally applied fields. Examples include stresses in hard materials, entropic fields in soft materials, and chemical potentials in both. The concept of field-assisted directed assembly is not material specific and the proposed research will serve as the general foundation for modeling and experimental design of directed nanoscale aggregation in a very broad range of materials. It may provide entirely new insights into the mechanisms of aggregation and reveal aspects that are common to practically all materials. At the same time, by exploiting common underlying characteristics, a deeper understanding will enable transfer of methodologies among different technological applications. Such unifying concepts are of paramount importance as high-tech materials are becoming more complex and ostensibly unrelated. Finally, the impact of this research on the education of graduate students is expected to be far reaching. It is increasingly apparent that a new generation of scientists and engineers is needed to lead the development of nanotechnology, which requires combined training in chemical engineering, materials science, and mechanics of materials. This closely-knit project will provide an ideal framework for this type of cross-disciplinary training. The research is being funded jointly by the Thermal Transport and Thermal Processing Program of the Chemical and Transport Systems Division, the Interfacial, Transport and Thermodynamics Program of the Chemical and Transport Systems Division, the Mechanics and Structures of Materials Program of the Civil and Mechanical Systems Division, and the Nanomanufacturing Program of the Design, Manufacturing and Industrial Innovation Division.