Self-Assembled Angle Independent Plasmonic Displays

自然界的颜色和色调令人惊叹--从五颜六色的花朵、鸟类和蝴蝶到鱼类和头足类等水下生物。这种颜色背后的机制与物种的不同一样不同，但可以分为两大类：色素沉着和结构颜色。在色素产生细胞中，分子吸收一部分可见光谱，而剩下的则被散射回观察者。另一方面，结构颜色是通过单元组或外部纳米结构内的反射、散射和干涉的组合产生的。在这两类中，结构色是几个极其生动的物种的原色产生机制。在自然界中，这些彩色显示器的关键方面是它们是由自组装的纳米结构在薄的、柔性的和曲线的表面上一致和均匀地形成的。这与最先进的人造显示器形成了鲜明对比，人造显示器仍然非常僵硬、脆弱，并且基于自上而下的处理。在这里，我们提出了一种大面积、高重复性的自组装技术，在超高真空电子束蒸发器中，通过依赖于温度和压力的薄膜生长机制在表面形成铝颗粒。该系统支持局限在粒子和反射镜之间的缝隙中的局域表面等离子激元，表现出高度独立于入射光的角度。共振的光谱位置可以根据铝颗粒的尺寸分布和周围介质的折射率进行调节。未被表面吸收的光线被反射回来，从而产生鲜艳的色彩。通过将自组装表面与液晶盒相结合，可以获得可主动调谐的等离子体显示器。该工艺也适用于大规模、柔性和扩散的衬底，从而可以产生具有可工程化材料和散射特性的新型等离子体表面/显示器。这项工作对于在柔性基板上开发低成本反射式显示器具有重要意义。新开发的自组装技术将使纳米结构表面的大面积图案化成为可能，以实现低成本制造。该项目为跨学科研究(包括集成光学、纳米制造和材料科学与工程)和研究生教育提供了一个很好的平台。这项研究将为丰富PI的研究生和本科教学提供令人振奋的科学内容。该计划将整合涵盖自闭症学生、K-12学生和其他代表性不足的少数族裔的外展活动。PI与奥兰多科学中心合作，对更广泛的社区进行非正式教育，并提高公众对显示器和一般颜色产生的认识。技术：在主动可调等离子领域有许多需要了解和开发的地方。经过多年的跨学科研究，基于液晶(LC)的快速响应、角度无关和扩散的可调显示器可以主动改变其像素的颜色，现在才有可能。我们计划通过深入分析自组装纳米结构表面的等离子体响应、液晶取向以及它们如何相互影响来进一步发展这一领域。该系统的一个关键目标是基于不依赖于照明角度或视角的自组装共振来设计与角度无关的漫射颜色表面。虽然这些等离子体表面易于产生颜色，但由于固有的窄带吸收，无法产生显示器所需的深黑色状态。这些显示设备的一个重要方面是能够控制从它们反射的光量。实现黑色和中等灰色状态的一种可能方式是使用液晶快门。由于低温制造工艺与PET等低玻璃化温度聚合物兼容，建议的器件可以很容易地在柔性基板上制造。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。

The range of colors and hues in the natural world are astonishing - from colorful flowers, birds and butterflies to underwater creatures like fish and cephalopods. The mechanisms underlying this color are as varied as the species, but can be broken into two main categories: pigmentation and structural color. In pigment producing cells, molecules absorb part of the visible spectrum while leaving the rest to be scattered back to the viewer. Structural color, on the other hand, is produced through combinations of reflection, scattering and interference within groups of cells or external nanostructures. Of these two classes, structural color serves as the primary color generating mechanism in several extremely vivid species. The key aspect of these color displays in nature is that they are consistently and uniformly formed from self-assembled nanostructures on thin, flexible and curvilinear surfaces. This in contrast to state-of-the-art manmade displays, which remain vastly rigid, brittle and based on top down processing. Here, we propose a large area, highly reproducible self-assembling technique where aluminum particles are formed on the surface through a temperature and pressure dependent thin film growth mechanism in an ultra-high vacuum electron beam evaporator. The system supports localized surface plasmons confined to the gaps between particles and the mirror which demonstrate a high degree of independence on the angle of incident light. The spectral location of the resonance can be tuned based on the size distribution of the aluminum particles and the index of the surrounding media. Light which is not absorbed by the surface is reflected back, resulting in a vivid perceived color. By integrating the self-assembled surface with liquid crystal cells, actively tunable plasmonic displays can be obtained. The process is also amiable to large-scale flexible and diffusive substrates which can result in novel plasmonic surfaces/displays with engineerable material and scattering properties. The proposed work is important for the development of low cost reflective displays on flexible substrates. The newly developed self-assembling techniques will enable large area patterning of nanostructured surfaces for low cost manufacturing. The program provides a good platform for interdisciplinary research (including integrated optics, nanofabrication and materials science and engineering) and graduate education. The research will generate exciting scientific content for enriching the PI's graduate and undergraduate teaching. The program will integrate outreach activities that span Autistic students, K-12 students and other underrepresented minorities. The PI collaborates with Orlando Science Center to informally educate the broader community and increase public awareness on displays and color generation in general.Technical: There is much to understand and develop in the field of actively tunable plasmonics. A fast response, angle independent and diffusive Liquid Crystal (LC) based tunable displays which can actively shift the color of its pixels is now possible only after years of interdisciplinary research. We plan on furthering this field through an in depth analysis of the plasmonic response of self-assembled nanostructured surfaces, LC orientation and how they influence each other. A key objective of the proposed system is to design angle independent and diffuse color surfaces based on a self-assembled resonance which doesn't depend on angle of illumination or viewing angle. While apt at producing color, these plasmonic surfaces cannot produce deep black states needed for displays due to intrinsic narrow band absorption. A vital aspect of these display devices is the ability to control the amount of light reflected from them. One possible way of achieving black and intermediate gray states is the use of liquid crystal shutter. The proposed device can readily be fabricated on flexible substrates as the low temperature fabrication process is compatible with low glassing temperature polymers such as PET.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.