Manufacturing a Robust Thermal Metamaterial Platform based on Carbon Nanolattices

虽然控制电和光的能力导致了电子和光子学的革命性进步，但控制热量的能力进展相对较小。这主要是由于对纳米尺度上的热传输的了解有限，以及缺乏旨在控制热传输的超材料。首席研究人员(PI)计划制造碳基蜂窝材料(即碳纳米晶格)，并建立一个热超材料的新领域。该项目开发的新的热传输和制造知识将指导未来超材料系统的设计，并使新型隔热材料和热整流器的开发成为可能。这项研究的成果将加强在热控、隔热和余热回收领域的创新，这将提高美国的能源生产，使研究直接影响经济福利和国家安全。研究成果将与教育活动和推广工作相结合。研究热传输机制或操纵热流的主要挑战之一是声子传输的扩散性质，当材料尺寸大于声子平均自由路径时，声子传输就会接管。PI将利用两个协同实验室的测量和处理能力来创建一个新的超材料平台，其特征尺寸小于声子平均自由路径。第一个目标是通过最先进的两步添加制造工艺来控制碳纳米晶格的尺寸、几何形状和纳米结构，该工艺包括双光子聚合直接激光写入聚合物模板，然后对模板进行热解。该工艺可以制备结构坚固、致密的聚合物晶格材料，特征尺寸在亚微米(200-1000 nm)范围内；通过精确控制裂解过程，PI将进一步提高分辨率，使碳结构的制造能够精确控制特征尺寸(20-200 nm)。同时，这一工艺允许实现用传统减法工艺难以制造的复杂三维(3D)几何图形，从而实现巨大的设计空间。通过同时优化晶格拓扑和热解碳纳米结构，该项目将利用导热系数中独特的尺寸效应。第二个目标是展示一种新的基于碳纳米晶格的热超材料平台，该项目将提供两个目标系统，包括提供低导热系数和高机械强度的独特组合的坚固的隔热材料，以及提供新颖的方向相关热传输特性的热整流器。该项目将确定架构化纳米晶格中的热传输机制，并开发多尺度和多功能的优化设计模型，其中包含尺寸效应并允许利用不对称几何结构。PIS将通过结合他们在热和机械科学、微尺度计量、3D制造和拓扑优化方面的互补专业知识来实现这些目标。这一奖项反映了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。

While the abilities to control electricity and light have led to revolutionary progress in electronics and photonics, the ability to control heat has made relatively little progress. This is mainly due to the limited understanding of thermal transport at the nanoscale and the lack of metamaterials designed to control heat transfer. The Principal Investigators (PIs) plan to manufacture carbon-based cellular materials (i.e. carbon nanolattices) and establish a new field of thermal metamaterials. The new thermal transport and manufacturing knowledge developed in this program will guide future designs of metamaterial systems and enable developments of novel thermal insulators and thermal rectifiers. The outcomes of this research will strengthen innovation in the areas of thermal control, thermal insulation, and waste heat recovery, which will enhance the energy production in the United States, so that the research directly impacts economic welfare and national security. The research outputs will be integrated with educational activities and outreach efforts.One of main challenges in studying thermal transport mechanisms or manipulating heat flows is the diffusive nature of phonon transport, which takes over when the material size is greater than the phonon mean-free-path. The PIs will utilize the measurement and processing capabilities of two synergistic labs to create a novel metamaterial platform with feature sizes smaller than the phonon mean-free-path. The first objective is to control size, geometry, and nanostructure of carbon nanolattices via a state-of-the-art two-step additive manufacturing process, consisting of two-photon polymerization direct laser writing of a polymeric template, followed by pyrolysis of the template. The process allows fabrication of structurally robust and dense polymeric lattice materials with feature sizes at the submicron range (200-1000 nm); by accurate control of the pyrolysis, the PIs will further improve the resolution, enabling fabrication of carbon structures with exquisite control of the feature size (20-200 nm). At the same time, this process allows realization of complex three-dimensional (3D) geometries that are difficult to fabricate with conventional subtractive processes, enabling an enormous design space. By simultaneously optimizing the lattice topology and the pyrolytic carbon nanostructure, the project will exploit unique size effects in thermal conductivity. The second objective is to demonstrate a new thermal metamaterial platform based on carbon nanolattices, and this project will present two target systems including a robust thermal insulator that offers a unique combination of low thermal conductivity and high mechanical strength, and a thermal rectifier that offers novel direction-dependent thermal transport properties. The project will identify thermal transport mechanisms in architected nanolattices and develop multiscale and multifunctional optimal design models that incorporate size effects and allow exploitation of asymmetric geometries. The PIs will achieve these objectives by combining their complementary expertise in thermal and mechanical sciences, microscale metrology, 3D manufacturing, and topology optimization.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.