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学和光子学的革命性进步，但控制热的能力却取得了相对较小的进展。这主要是由于对纳米尺度的热传递的理解有限，以及缺乏设计用于控制热传递的超材料。主要研究人员（pi）计划制造碳基细胞材料（即碳纳米晶格），并建立一个新的热超材料领域。在这个项目中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，并使新型隔热体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制、隔热和余热回收领域的创新，这将提高美国的能源生产，从而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外联努力结合起来。研究热输运机制或控制热流的主要挑战之一是声子输运的扩散性质，当材料尺寸大于声子平均自由程时，声子输运就会发生扩散。pi将利用两个协同实验室的测量和处理能力来创建一个特征尺寸小于声子平均自由程的新型超材料平台。第一个目标是通过最先进的两步增材制造工艺控制碳纳米晶格的尺寸、几何形状和纳米结构，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。该工艺允许制造结构坚固且致密的聚合物晶格材料，其特征尺寸在亚微米范围（200-1000纳米）；通过对热解的精确控制，pi将进一步提高分辨率，从而能够精确控制特征尺寸（20-200 nm）的碳结构的制造。同时，该工艺允许实现复杂的三维（3D）几何形状，这是传统减法工艺难以制造的，从而实现了巨大的设计空间。通过同时优化晶格拓扑和热解碳纳米结构，该项目将利用独特的尺寸效应在导热性。第二个目标是展示一种基于碳纳米晶格的新型热超材料平台，该项目将展示两个目标系统，包括提供低导热性和高机械强度独特组合的坚固隔热体，以及提供新型方向相关热输运特性的热整流器。该项目将确定纳米晶格结构中的热传输机制，并开发包含尺寸效应和允许利用不对称几何的多尺度和多功能优化设计模型。pi将通过结合他们在热学和机械科学、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。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.