CAREER: Magnetically Tunable Photonic Crystal Structures

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TECHNICAL SUMMARYPhotonic materials with properties that can be tuned by external stimuli have important applications in areas such as color displays, biological and chemical sensors, inks and paints, or active optical components. This proposal, supported by the Solid State and Materials Chemistry (SSMC) and Electronic and Photonic Materials (EPM) programs in the Division of Materials Research (DMR) and the Particulate and Multiphase Processes program in Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET), aims to develop an integrated self-assembly approach for building magnetically responsive photonic crystal structures with photonic properties rapidly and widely tunable using external magnetic fields. The main strategy is to design the superparamagnetic colloidal building blocks in accordance to the liquid media so that a strong interparticle repulsion exists to balance the magnetically induced attraction force and eventually induce the self-assembly of particles into ordered structures. By changing the strength of the magnetic field, the periodicity and consequently the photonic property can be rapidly tuned. Through manipulation of surface chemistry of the magnetic particles, electrostatic, solvation and steric forces will be employed as repulsive forces countering the magnetically induced attractive forces for optimal assembly. Unlike conventional colloidal assembly approaches, this new strategy allows instant creation of photonic crystal structures, and rapid and fully reversible tuning of the photonic properties in a wide spectrum range, thus providing a new platform for many photonic applications. This proposal also explores the use of this self-assembly approach and the magnetically tunable photonic systems for applications such as full-color high resolution printing and rewritable photonic papers.NON-TECHNICAL SUMMARY: The proposed research will develop a unique self-assembly approach for the preparation of photonic structures whose color can be changed rapidly and reversibly by applying an external magnetic field. Upon establishing a balance between the repulsive and attractive interactions, magnetic colloidal particles can be instantly assembled into ordered structures with photonic properties that are tunable by changing the strength of the magnetic field. These responsive photonic structures will have important applications in areas such as color displays, biological and chemical sensors, inks and paints, or active optical components. The proposed research efforts will be closely integrated with educational outreach to promote the interest of students, especially those from underrepresented groups, in science and engineering. Results from the proposed research will be incorporated into a new core course "Nanoscience and Nanotechnology" offered to graduate and senior undergraduate students at the UC Riverside. Undergraduate students from UCR and local small liberal arts colleges and local high school students will be recruited and given the opportunity to conduct related research through regular academic and summer internship programs. Onsite and online exhibitions will be developed through partnerships with museums, science centers, and educational websites to broadly disseminate the research results and to enhance the public's understanding of science and technology. Effective collaborations with researchers at UCR, industry, national laboratories, and international research groups will be established during the project period.