Realizing Hierarchically Ordered Porous Functional Materials from the Crystallization of Both Large-scale and Colloidal Particles

有序多孔材料有望在各种领域提高性能。这类材料通常是通过一种称为自组装的过程来制造的，通过这种过程，宏观材料的组成部分自发地将自己排列成所需的结构。虽然纳米级材料的自组装最近吸引了科学家和工程师的兴趣和想象力，但更大的中观和宏观组件的自组装也可以对组织工程、微电子、能源和3-D视觉显示产生巨大影响。然而，尽管有这些技术驱动因素，但这些较大规模的自我组装几乎没有受到科学界和工程界的关注，这一领域仍处于初级阶段。该奖项支持研究和开发适合制造有序多孔材料的自组装方法，这些材料由比纳米材料大得多的积木构成(即在几十到数百或微米的尺寸范围内)。除了将自组装方法开放给一系列全新的构建块外，这一领域的成功项目还将允许将新技术与现有的纳米级方法相结合，最终导致制造出可按前所未有的尺寸范围订购的材料。预计这类新材料将在组织工程(支架)、燃料电池/电池电极制造到制药等领域的应用中取得进展，因此，这项研究的结果将造福于美国整体经济和社会。这项研究结合了化学、物理、工程和材料科学的专业知识。这种多学科的方法将有助于扩大未被充分代表的群体在研究中的参与，并对工程教育产生积极影响。胶体结晶是纳米级粒子自组装的主要手段，然而直到最近，这项技术基本上还没有在几微米以上的规模上使用。这在一定程度上是因为，在这些较大的中观和宏观尺度上，潜在的热效应(即布朗运动)足够小，以至于组分在非平衡状态下被动力学阻止。研究小组计划结合实验和建模(离散元素和格子Boltzmann耦合方法)，以进一步开发一系列有前景的新材料处理策略，利用最近发现的大范围(10微米到100微米)稀薄流体-颗粒系统的不稳定性。理论和尺度论证将被用来确定诱导所需不稳定性所需的标准。这些新策略将使颗粒结晶技术适用于一系列通常远远超出胶体极限的颗粒尺寸。然后，现有(胶体)技术和新方法的组合可以用来制造新的层次化有序结构，这些结构模仿自然界中发现的结构(无论是在孔分布还是化学计量)，并最终形成新的材料加工方法的基础。

Ordered porous materials hold promise for enhanced performance in a variety of fields. Often this class of materials are fabricated through a process called self-assembly, whereby the component parts of a macroscopic material spontaneously arrange themselves into a desired structure. While self-assembly of materials that are ordered at the nano-scale has recently captured the interest and imagination of scientists and engineers, the self-assembly of larger, meso- and macro- scale components can also have a dramatic impact on tissue engineering, microelectronics, energy, and 3-D visual displays. Nevertheless, despite these technical drivers, self-assembly at these larger scales has received little focus from the scientific and engineering communities and this area remains in its infancy. This award supports the study and development of methods of self-assembly that are amenable to the fabrication of ordered porous materials constructed of building blocks that are considerably larger than nano-materials (that is, in the tens to hundreds or micrometer size range). In addition to opening the approach of self-assembly to a whole new range of building blocks, a successful project in this area will also allow a combination of the new techniques with existing nano-scale methods to ultimately lead to the fabrication of materials that are ordered over an unprecedented range of size scales. It is expected that this new class of materials can lead to advances in applications ranging from tissue engineering (scaffolds) to fuel cell/battery electrode fabrication to pharmaceuticals, thus, results from this research will benefit the U.S. economy and society as a whole. This research involves combining expertise in chemistry, physics, engineering, and materials science. The multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.Colloidal crystallization is a staple of nano-scale particle self-assembly, however, until recently is has been a technique that was essentially unused at scales beyond several microns. This is due, in part, to the fact that the underlying thermal effects (i.e., Brownian motion) at these larger meso- and macro- scales are small enough that components become kinetically arrested in non-equilibrium states. The research team plans to use a combination of experimentation and modeling (coupled Discrete Element and Lattice Boltzmann methods) in order to further develop a promising series of new materials processing strategies that exploit recently uncovered instabilities of dilute fluid-particle systems at large (10s to 100s of microns) scales. Theoretical and scaling arguments will be used to determine the criteria necessary to induce the required instabilities. These new strategies will open particle crystallization techniques to a range of particle sizes that are typically well beyond the colloidal limit. Then, a combination of existing (colloidal) techniques with the new approaches can be used to fabricate novel hierarchically-ordered structures that mimic those found in nature (both in pore distribution as well as stoichiometry) and can ultimately form the basis of novel materials processing methods.