Smart regulation of thermal infrared radiation with meta-structured metal-insulator transition

非技术性：红外（IR）图像是由红外摄像机捕获热物体的热红外辐射产生的。该过程在夜视、热成像、遥感、医学成像和建筑物监控方面有广泛的应用。尽管付出了巨大的努力，但真正的创新是为了满足快速发展的现代社会的需求。红外成像是一个两步过程。功率从热表面辐射，然后通过红外摄像机转换为电信号。目前提高热成像灵敏度的努力集中在改进相机上，因为辐射功率被认为受到物理定律的限制，该物理定律规定了在给定温度下从物体辐射的IR功率的量。因此，红外成像的温度灵敏度限制在~ 0.04 ℃。然而，这种灵敏度不够精细，并且阻止了IR成像的一些关键应用。PI将通过克服限制辐射功率的物理定律来推进红外成像。PI将开发一种涂层材料，在选定的温度范围内大幅提高红外辐射功率。这将有效地将物体的有效温度变化放大为IR成像温度的大变化。因此，使用传统相机的红外成像的温度灵敏度提高了15倍以上，达到0.003摄氏度以下。这样的改进使得能够灵敏地检测集成电路中的弱缺陷、皮肤下肿瘤的早期诊断以及表面下建筑裂缝的检查。涂层材料还可以用于实现可切换的辐射冷却，以在表面温度高于预设温度时冷却表面。即将开发和部署的新设备将推动热成像和辐射冷却的边界远远超出最先进的水平，为潜在的商业化提供巨大的价值。与研究工作相结合，PI还提出了一个教育计划，将刺激和准备大学预科学生在工程职业生涯中与红外技术有关。技术：该项目的目标是展示智能，以前不存在的热红外调节设备，用于超灵敏的次表面红外成像和可切换的辐射冷却。PI计划通过解除其限制来重新想象热辐射的Stefan-Boltzmann定律，以实现红外成像灵敏度的数量级增强。具有与等离子体共振集成的金属-绝缘体转变的材料能够实现热辐射的大切换，这是在任何常规材料中都没有发现的特性。金属-绝缘体转变通过掺杂和等离子体共振进行设计，以实现前所未有的温度相关发射率的物理特性，这是该提案的关键创新。钨掺杂大大扩展了二氧化钒的工作温度范围，而微图案化的超光子设计反转并放大了整个过渡区的红外辐射对比度。在可调和预设温度下，表面发射率的转换为智能调节热红外辐射奠定了材料基础：红外成像灵敏度的大幅增强，以及辐射冷却的可转换性。该奖项反映了NSF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。

Nontechnical:Infrared (IR) images are produced by IR cameras capturing thermal IR radiation from hot objects. This process has a wide range of applications in night vision, thermography, remote sensing, medical imaging, and building monitoring. Despite extensive efforts, true innovations are sought to meet the needs of the rapidly advancing modern society. IR imaging is a two-step process. Power is radiated from a hot surface and then converted to an electrical signal by an IR camera. Current efforts to improve thermal imaging sensitivity focus on improving the camera, because the radiated power is believed to be limited by a physical law that dictates the amount of IR power radiated from the object at given temperature. Consequently, the temperature sensitivity for IR imaging is limited to ~ 0.04 degree C. However, this sensitivity is not fine enough, and prevents some critical applications of IR imaging. The PI will advance IR imaging by overcoming the physical law that limits radiated power. The PI will develop a coating material that drastically boosts the radiated IR power within a selected temperature range. This will effectively amplify the effective temperature variation of the object into large variation of IR imaged temperature. As a result, the temperature sensitivity of IR imaging with a conventional camera is improved by a factor of over 15, to below 0.003 degree C. Such an improvement enables sensitive detection of weak defects in integrated circuits, early diagnosis of sub-skin tumors, and inspection of sub-surface building cracks. The coating material can also be used to implement switchable radiative cooling to cool a surface when its temperature is higher than the preset temperature. The new devices to be developed and deployed will push the boundary of thermal imaging and radiative cooling much beyond the state-of-the-arts, promising great values for potential commercialization. Integrated with the research effort, the PI also proposes an educational program that will stimulate and prepare pre-college students for careers in engineering pertaining to infrared technologies.Technical:The goal of this project is to demonstrate smart, previously non-existing thermal IR regulation devices for ultra-sensitive sub-surface IR imaging and switchable radiative cooling. The PI plans to accomplish the goal by re-imagining the Stefan-Boltzmann law of thermal radiation by lifting its limitation, to achieve orders of magnitude enhancement in IR imaging sensitivity. Materials with metal-insulator transition integrated with plasmonic resonance enable a large switching in thermal radiation, a property not found in any conventional materials. The metal-insulator transition is engineered with doping and plasmonic resonance to achieve unprecedented physical properties of temperature-dependent emissivity, which are the key innovations in this proposal. Tungsten-doping substantially expands the working temperature range of vanadium dioxide, while micro-patterned metaphotonic design reverses and amplifies the contrast in IR radiation across the transition. The resultant switching in surface emissivity at tunable and preset temperatures lays the materials foundation to smart regulation of thermal IR radiation: drastic enhancement in IR imaging sensitivity, and switchability in radiative cooling.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.