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

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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.