Collaborative Research: Liquid Metal Tuned Flexible Metasurfaces

非技术：光学窗口，如处方眼镜的镜片是可以合理定制的。透镜可以在大小、形状、曲率或设计上有所不同。除了美观的特点，功能和整体包装也可以修改或升级。例如，可以添加抗反射涂层来减少眩光，而光致变色透镜可以抑制暴露在紫外线辐射下的光透射。这些可选的特性对物理性能的影响最小，因为这样的涂层增加的厚度不到一毫米。微波窗可以看作是在微波光谱中起作用的一种光学窗口。与光学窗一样，微波窗是用来传输、反射或吸收电磁波的。微波窗是雷达罩（保护雷达天线的外壳）和减少电磁干扰的屏蔽等系统中不可或缺的组件。与光学窗不同的是，目前的设计技术并没有提供太多的自由来定制微波窗的功能和物理特性。例如，实际的微波窗口是灵活的，厚度可定制的，并且可以根据需要实时调整传输响应仍有待实现。该项目将开发可应用于实现液态金属可调谐和机械柔性多层微波窗口的新技术。该装置将通过集成可移动的液态金属来制造，这种金属可以以最小的损耗提供广泛的调谐范围。由此产生的概念可以适用于所有类型的滤波器，在实现多层可调谐/柔性微波窗口时提供前所未有的设计控制。教育和推广计划的重点是来自代表性不足群体的学生，将研究成果融入pi教授的课堂课程，并与行业开展积极合作。技术：本提案的目标是研究新的理论基础，并探索液态金属调谐机械柔性（可弯曲/可折叠）超表面的潜力和局限性。该技术方法依赖于采用基于厚度可定制互耦层的多层超表面合成技术，这些互耦层具有导纳逆变器的功能。所提出的液态金属调谐机械柔性超表面由聚二甲基硅氧烷（PDMS）微流控通道中的镓基液态金属塞作为可移动调谐元件和另一种以特定图案填充的镓合金作为固定金属组成。这些液态金属塞将不含氧化物，并在微流体通道中自由移动。因此，可动液态金属段塞序列在大型二维阵列超表面上的位置可实现高精度气动调谐。微波窗口的可重构特性使得微波窗口对于在动态电磁环境下工作时需要可控/稳定高频响应的广泛应用具有吸引力。当与灵活性特性相结合时，新技术可以通过实现可部署、可移动和可适应的元表面来彻底改变下一代微波窗口的使用，这些元表面可以按需实时调整。最终结果是超表面技术的重大科学飞跃，并为未来基于超表面的设备和系统建立了原理和新技术的可行性。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。

Nontechnical:Optical windows such as lenses in prescription glasses are reasonably customizable. Lenses can vary in size, shape, curvature, or design. In addition to aesthetic features, the functionalities and overall packaging can also be modified or upgraded. For example, anti-reflective coatings can be added to reduce glare and photochromic lenses suppress light transmission on exposure to ultraviolet radiation. These optional features have minimal impact on physical properties since such coatings add less than a millimeter of thickness. Microwave windows can be considered as a type of optical window that functions in the microwave spectrum. As with optical windows, microwave windows are made to transmit, reflect, or absorb electromagnetic waves. Microwave windows are indispensable components in systems such as radomes (enclosures that protect a radar antennas) and shields that reduce electromagnetic interference. Unlike optical windows, current design techniques do not lend much freedom to customize both functional and physical characteristics of the microwave windows. For example, practical microwave windows that are flexible, thickness customizable, and can tune the transfer response on-demand in real-time remain to be realized. This project will exploit new techniques that can be applied to realize liquid metal enabled tunable and mechanically flexible multi-layered microwave windows. The proposed device will be made by integrating movable liquid metals that can provide a wide tuning range with minimal loss. The resulting concept can be adapted to all types of filters, delivering unprecedented design control in the implementation of multi-layered tunable/flexible microwave windows. The educational and outreach plan focuses on students from underrepresented groups, integrating research findings into classroom courses taught by the PIs and developing active collaboration with industry.Technical:The objectives of this proposal are to study new theoretical foundations and explore the potentials and limitations of liquid metal tuned mechanically flexible (bendable/foldable) metasurfaces. The technical approach relies on adopting a multi-layer metasurface synthesis technique based on thickness customizable intercoupling layers that behave as admittance inverters. The proposed liquid metal tuned mechanically flexible metasurfaces consist of gallium-based liquid metal slugs in polydimethylsiloxane (PDMS) microfluidic channels as moveable tuning elements and another gallium alloy filled in specific metasurface pattern as fixed metal. These liquid metal slugs will be made oxide free and freely movable in the microfluidic channel. Thus, the position of the moveable liquid metal slug train in a large 2D array metasurface can be tuned pneumatically with high precision. The reconfigurable property makes microwave windows attractive for a wide range of applications that demand controllable/stable high-frequency response when operated under a dynamic EM environment. When combined with the flexibility feature, the new technology can revolutionize the use of next-generation microwave windows by enabling deployable, transportable, and conformable metasurfaces that can be tuned on-demand, in real-time. The end result is a significant scientific leap in metasurface technology and establishment of the principles and the feasibility of new technologies for future metasurface-based devices and systems.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.