Building reconfigurable photonic materials and devices by light-guided self-assembly of nanoparticles

非技术描述纳米科学的一个吸引人的前景是能够用纳米级的积木来构建新型的电子和光子材料。化学合成的纳米颗粒具有良好控制的大小和形状，使人们能够定制材料或结构的属性。能够将纳米颗粒重新组装成新的形状，将使科学家和工程师能够构建能够对刺激做出反应的多功能材料。可重构组装在生物系统中很常见，但在人造纳米材料中仍然很少见。例如，眼睛的晶状体会改变以调整焦距，或者虹膜在明亮的光线下收缩。然而，目前用于组装纳米颗粒的方法大多导致具有固定大小和形状的结构。该项目通过使用光以受控的方式将纳米颗粒组装成可重新配置的形状来满足这一需求。这将通过将激光光束整形成结构化光场并研究与纳米颗粒的相互作用来实现。研究小组将测量纳米颗粒阵列的光学、电子和机械性能，旨在展示光驱动纳米电机和生物传感器等新应用。该项目还将启用一个名为“iPhotons”的新的远程访问教育平台，这是一个可上网的全息光学镊子和光学纳米材料模拟平台。IPhotons平台类似于研究系统，因此许多从研究活动中衍生出来的技术可以移植到这个平台上。支持本科生和研究生研究人员，特别是那些来自STEM中代表性不足的群体的研究人员，开发研究技术，建造iPhoton，并帮助远程用户。因此，iPhotons不仅使大学研究人员受益，而且通过现有的外联计划使K-12学生和公众受益。该项目共同推进了材料和光子学的基础科学，并促进了更广泛的人的教学、培训和学习。技术说明该项目通过胶体纳米颗粒在光引导下组装来构建可重构的光子材料和器件，并进一步揭示了它们的集体性质和潜在应用。这项研究解决了纳米科学中的一个基本挑战，即以受控的方式将纳米颗粒重新组装成所需的结构。研究小组利用激光束的动量来诱导和控制纳米颗粒的电动力学相互作用(即光学结合)。采用实验和计算相结合的方法来理解纳米尺度的光学结合，实现可重构的光导组装。首先，研究小组调查了纳米粒子的大小、形状和材料对其光学结合相互作用和自组装行为的影响。其次，该团队能够将纳米颗粒自组装成具有协同强度、相位、偏振和波长的可重新配置的组件(即光学物质)。先进的全息光束整形方法被用来雕刻激光场的光学景观并控制纳米颗粒的组装。第三，该团队测量光学物质的集体光子性质，如表面晶格共振、二次谐波产生和表面增强拉曼散射。最后，该团队展示了光学物质簇作为光机械纳米马达和生物传感器的新应用。总之，该项目建立了纳米粒子可重构组装的新技术，丰富了离散等离子体纳米粒子阵列的光子世界，并使可重构光学物质成为多功能光子材料和器件。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。

Non-technical DescriptionAn attractive prospect of nanoscience is the ability to build novel electronic and photonic materials with nanoscale building blocks. Chemically synthesized nanoparticles with well-controlled size and shape allow one to tailor the properties of a material or structure. Being able to reassemble nanoparticles into new shapes will allow scientists and engineers to build multifunctional materials that can respond to stimuli. Reconfigurable assembly is common in living systems but still rare in artificial nanomaterials. For example, the lens of an eye changes to adjust focus or the iris contracts in the presence of bright light. However, current approaches for the assembly of nanoparticles mostly lead to structures with fixed size and shape. This project addresses this need by using light to assemble nanoparticles into reconfigurable shapes in a controlled manner. This will be achieved by shaping a laser beam into structured optical fields and studying interactions with nanoparticles. The research team will measure the optical, electronic, and mechanical properties of nanoparticle arrays, aiming to demonstrate new applications such as light-driven nanomotors and biosensors. The project will also enable a new remote-access education platform named “iPhotons”, an internet-accessible Platform for Holographic Optical Tweezers and Optical Nanomaterial Simulations. The iPhotons platform resembles the research system, so many techniques derived from the research activity can be transferred to this platform. Undergraduate and graduate researchers, especially those from underrepresented groups in STEM, are supported to develop the research techniques, build the iPhotons, and assist remote users. Therefore, the iPhotons benefits not only university researchers, but also K-12 students and the public through existing outreach programs. Together, this project advances fundamental sciences in materials and photonics, and promotes teaching, training, and learning to a wide range of people.Technical DescriptionThis project builds reconfigurable photonic materials and devices by light-guided assembly of colloidal nanoparticles, and further reveals their collective properties and potential applications. The research addresses a fundamental challenge in nanoscience, which is the reconfigurable self-assembly of nanoparticles into desired architectures in a controlled way. The research team uses the momentum of a laser beam to induce and control the electrodynamic interactions (i.e., optical binding) of nanoparticles. A combined experimental and computational approach is used to understand the nanoscale optical binding and realize reconfigurable light-guided assembly. First, the team investigates the influence of the size, shape, and material of nanoparticles to their optical binding interactions and self-assembly behaviors. Second, the team enables self-assembly of nanoparticles into reconfigurable assemblies (i.e., optical matter) with synergized intensity, phase, polarization, and wavelength of light. Advanced holographic beam shaping methods are used to sculpt the optical landscape of a laser field and control the assembly of nanoparticles. Third, the team measures the collective photonic properties of the optical matter, such as surface lattice resonances, second harmonic generation, and surface-enhanced Raman scattering. Lastly, the team demonstrates new applications of optical matter clusters as optomechanical nanomotors and biosensors. In sum, this project establishes a new technology for reconfigurable assembly of nanoparticles, enriches the photonic world of discrete plasmonic nanoparticle arrays, and enables reconfigurable optical matter as multifunctional photonic materials and devices.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.