CAREER: Scalable Manufacturing of Hierarchical Nanostructures by Acoustically Modulated Emulsion Technique for Next Generation Renewable Energy Applications

将纳米积木组装成分层结构可以生产出具有前所未有的性能和功能的新型材料，特别是在包括大容量电池和高效太阳能电池在内的下一代可再生能源应用中，从而确保国家的能源未来和繁荣。制造具有长程有序的分级纳米结构的现有方法需要使用在制造可伸缩性、成本和时间方面受限的模板。在三维结构中产生受控的成分变化方面，它们也落后于人。该奖项支持基础研究，以产生研究简易过程所需的知识，以生成可伸缩和可重新配置的三维模板，用于定向组装具有合理设计的结构、拓扑、组成和长程有序的层次化纳米结构。这项研究促进了对自组装过程的科学理解，并提供了通过工程环境来指导组装的策略。由于组装过程在自然界中是常见的，例如，活细胞按照层级顺序组装成功能器官，来自这项研究的知识有助于理解生命和生命工程，这影响了NSF关于“理解生命规则”的大想法。多学科研究涉及声学、流体动力学、材料科学和制造，为本科生和研究生提供独特的培训和研究机会。该项目让社区大学生，特别是那些来自代表不足的少数族裔的学生参与研究，帮助他们在科学和工程方面取得学术成就。通过声音调制乳剂引导的分级纳米结构的组装可以克服现有组装方法的几个局限性，包括远程无序结构、高成本、长时间、低可伸缩性、成分和各向异性的有限控制。然而，要充分开发分级纳米结构的应用潜力，还需要克服基本的科学障碍。本研究旨在填补Pickering乳化液体系中纳米颗粒和纳米颗粒液滴在恒定声场作用下的动力学知识空白。该项目进行多尺度分子动力学和有限元模拟，并结合实验验证，研究纳米颗粒和乳化液液滴的动力学，并描绘关键工艺变量的影响。在基础研究的基础上，设计和开发了声调乳胶系统，以制备一套设计合理、在纳米和微米尺度上具有结构、拓扑和成分各向异性的金属氧化物分级纳米结构。以二氧化钛基染料敏化太阳能电池为模型器件，建立了纳米和微尺度的结构和成分各向异性与宏观材料特性和器件性能的关联。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。

Assembling nano building blocks into hierarchical structures can produce novel materials with unprecedented performance and functionalities, especially for next-generation renewable energy applications, including high-capacity batteries and high-efficiency solar cells, thus securing the energy future and prosperity of the nation. Existing methods to manufacture hierarchical nanostructures with long-range order require the use of templates that are limited in terms of fabrication scalability, cost, and time. They also lag behind on generating controlled composition variations in three-dimensional structures. This award supports fundamental research to produce needed knowledge for the study of a facile process to generate scalable and reconfigurable three-dimensional templates for the directed assembly of hierarchical nanostructures with rationally designed structure, topology, composition, and long-range order. This research promotes scientific understanding of the self-assembly process and provides strategies to direct the assembly by engineering the environment. Since assembly process is common in nature, e.g., living cells assemble into functional organs following a hierarchical order, knowledge from this research contributes to the understanding of life and life's engineering, which impacts the NSF Big Idea of 'Understanding the Rules of Life'. The multi-disciplinary research, involving acoustics, fluid dynamics, materials science and manufacturing, provides unique training and research opportunities to undergraduate and graduate students. The project involves community college students, especially, those from under-represented minorities, in research and help achieve academic success in science and engineering.The assembly of hierarchical nanostructures directed by acoustically-modulated emulsion can overcome several limitations existing assembly methods have, including disordered structures in long range, high cost, lengthy time, low scalability, and limited control of composition and anisotropy. However, fundamental scientific barriers are yet to be overcome to fully exploit the application potential of hierarchical nanostructures. This research is to fill the knowledge gap on the dynamics of nanoparticles and nanoparticle-loaded droplets in the Pickering emulsion system when subjected to a standing acoustic field. The project performs multi-scale molecular dynamics and finite element simulation, coupled with experimental validation, to investigate the dynamics of nanoparticles and emulsion droplets and delineate the effects of key process variables. Based on the fundamental studies, acoustically-modulated emulsion systems are designed and developed to manufacture a set of rationally designed metal oxide hierarchical nanostructures with structural, topological and compositional anisotropy in both nano- and micro- scales. Using titanium dioxide-based dye sensitized solar cell as a model device, the correlation of nano- and micro- scale structural and compositional anisotropy with the macroscale material properties and device performances are established.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.