Fundamental Investigations in Femtosecond Laser-based Additive Manufacturing with Functional Nanomaterials

随着物联网（IoT）时代的到来，对于用于各种生物医学和环境监测应用的小型化智能设备（诸如智能沙、标签和可穿戴/可植入设备）的需求日益增加。这些设备中的许多关键组件，如传感器、天线、互连和电池，与半导体行业中使用的传统集成电路（IC）工艺不兼容。此外，许多器件需要针对其特定的目标应用进行定制，这可能需要三维纳米结构、异质材料集成、小型化外形以及指定的灵敏度、功率密度和寿命。由于工艺和材料选择缺乏灵活性，传统半导体制造厂难以适应这些定制规格。微米和纳米级增材制造有可能满足这些要求。然而，在这一领域仍然需要技术突破，以实现具有与IC制造设备相称的纳米级分辨率、质量和可靠性的功能组件的增材制造。该奖项支持基础研究，以形成用于直接制造纳米器件的纳米级增材制造（Nano-AM）工艺开发的知识基础。这项研究涉及多个学科，包括纳米制造，激光-纳米材料相互作用，表面科学和多尺度传输现象。这项研究的结果将通过在物联网时代提供改变范式的制造技术来提高美国在先进制造业中的竞争力。将研究成果整合到课程开发、本科生和少数民族学生的研究机会以及K-12学生的实践项目中，将提高学生的知识水平，促进先进制造业的创新。目前的纳米增材制造受到缺乏制造3D非聚合物功能器件能力的限制。为了克服这一限制，本研究采用非聚合物（金属，半导体和电介质）纳米材料作为构建模块，旨在了解和利用这些纳米材料在超快激光激发下的独特行为，以实现3D Nano-AM工艺。首先，探讨飞秒激光诱导纳米材料电离和表面改性的基本机理。其次，将建立激光激发（电离和改性）与诱导纳米材料组装、沉积和烧结行为之间的相关性。将进行多尺度建模和模拟（从头算，经典分子动力学和布朗动力学），以了解不同时间和空间尺度上的实验结果。最后，将开发一个基于物理的模型，将纳米材料的特性、激光激发条件与纳米结构的形态和特性联系起来。

With the coming era of the Internet-of-Things (IoT), there is an increasing need for miniaturized smart devices, such as smart sands, tags, and wearable/implantable devices, for various biomedical and environmental monitoring applications. Many critical components in these devices, such as sensors, antennas, inter-connects and batteries are not compatible with conventional Integrated Circuits (IC) processes used in the semiconductor industry. In addition, many devices need to be customized for their specific target applications, which could require three-dimensional nanostructures, heterogeneous materials integration, miniaturized form factor, and specified sensitivity, power density and life times. It is difficult for conventional semiconductor manufacturing foundries to accommodate these customized specifications due to the lack of flexibility in process and material choices. Micro and nanoscale additive manufacturing has the potential to meet such requirements. However, a technical breakthrough is still needed in this area to enable additive manufacturing of functional components with nanoscale resolution, quality and reliability commensurate with IC fabricated devices. This award supports fundamental research to form the knowledge base for development of nanoscale additive manufacturing (Nano-AM) processes for direct manufacturing of nano-devices. Multiple disciplines are involved in this research including nanomanufacturing, laser-nanomaterial interaction, surface science, and multiscale transport phenomena. Results from this research will enhance the U.S. competence in advanced manufacturing industry by providing paradigm-changing manufacturing technique in the era of IoT. The integration of the research results into curriculum development, undergraduate and minority students research opportunities and hands-on projects for K-12 students will enhance the students' knowledge and foster innovation in advanced manufacturing.Current nanoscale additive manufacturing is limited by the lack of capability to fabricate 3D nonpolymer functional devices. To overcome this limit, this research employs non-polymer (metal, semiconductor and dielectric) nanomaterials as building blocks and aims at understanding and exploiting unique behaviors of these nanomaterials under ultrafast laser excitation to enable 3D Nano-AM processes. Firstly, fundamental mechanisms leading to femtosecond laser induced ionization and surface modification of nanomaterials will be explored. Secondly, the correlations between laser excitation (ionization and modification) and induced nanomaterial assembly, deposition and sintering behaviors will be established. Multiscale modeling and simulations (Ab initio, classical Molecular Dynamics and Brownian Dynamics) will be performed to understand experimental results over different temporal and spatial scales. Finally, a physics-based model relating nanomaterials properties, laser excitation conditions with the morphology and properties of manufactured nanostructures will be developed.