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捉热物体发出的红外辐射而产生的。这一过程在夜视、热成像、遥感、医学成像和建筑监控等领域有着广泛的应用。尽管付出了广泛的努力，但人们仍在寻求真正的创新，以满足快速发展的现代社会的需求。红外成像是一个分两步进行的过程。电力从炽热的表面辐射出来，然后由红外摄像机转换成电信号。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一个物理定律的限制，该定律规定了物体在给定温度下辐射的红外功率的量。因此，红外成像的温度灵敏度被限制在~0.04℃，然而，这种灵敏度还不够精细，阻碍了红外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改进红外成像。PI将开发一种涂层材料，在选定的温度范围内显著提高辐射红外功率。这将有效地将物体的有效温度变化放大为红外成像温度的较大变化。结果，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。这种改进使人们能够灵敏地检测集成电路中的微弱缺陷，早期诊断皮下肿瘤，并检查亚表面建筑裂缝。该涂层材料还可用于在表面温度高于预设温度时实现可切换辐射冷却。即将开发和部署的新设备将把热成像和辐射冷却的界限推向最先进的水平，有望实现巨大的商业化价值。结合研究工作，PI还提出了一项教育计划，将刺激和准备大学预科学生在与红外技术有关的工程领域的职业生涯。技术：该项目的目标是展示用于超灵敏亚表面红外成像和可切换辐射冷却的智能、以前不存在的热红外调节设备。PI计划通过重新想象Stefan-Boltzmann热辐射定律来实现这一目标，通过取消其限制来实现红外成像灵敏度的数量级增强。金属-绝缘体转变与等离子体共振相结合的材料能够实现热辐射的大开关，这是任何传统材料所没有的特性。金属-绝缘体的转变是通过掺杂和等离子体共振来实现前所未有的随温度变化的发射率的物理性质，这是这一提议的关键创新。钨掺杂大大扩展了二氧化钒的工作温度范围，而微图案化的超光设计反转并放大了过渡期间红外辐射的对比度。由此产生的表面发射率在可调和预设温度下的转换为智能调节热红外辐射奠定了材料基础：红外成像灵敏度大幅增强，辐射冷却可切换。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。

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.