CAREER: Evaporation-Driven Self-Assembly of Hierarchically Ordered Structures from Confined Solutions

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0844084Z. LinThe goal of this CAREER proposal is to develop a simple, yet robust, one-step method via evaporation for creating nanostructured materials with hierarchical order in a precisely controllable manner, dispensing with the need for lithographic techniques and external fields. To achieve this goal, two specific objectives are proposed: (1) create hierarchically ordered structures via the synergy of evaporation-driven self-assembly at the microscopic scale and spontaneous self-assembly at the nanoscopic scale; and (2) develop theoretical models to understand the mechanisms of structure formation. We intend to design hierarchical structures consisting of either diblock copolymers or quantum dots (QDs) self-assembled at the nanoscale that can serve as multifunctional materials for potential applications in optical, electronic, optoelectronic, and sensing materials and devices. Hierarchically ordered structures are produced by combining two or more self-assembling processes on different length scales, i.e., dynamic self-assembly via irreversible solvent evaporation in restricted geometries (i.e., curve-on-flat geometries) at the microscopic scale and spontaneous self-assembly of diblock copolymers or QDs at the nanoscale. This approach utilizes concurrent self-assemblies as a means to precisely organize unique nanomaterials into spatially ordered structures. The research findings will be treated within the broader context of nanomaterials science and utilized for nanoscience and nanotechnology education. Integrated educational activities will be developed to expose a wide range of audiences, including K-12 students, to this new nanoscience and nanotechnology knowledge, thereby promoting general awareness of its importance. The intellectual merit of the proposed research is manifested in the innovative studies of exploiting restricted geometries (i.e., curve-on-flat geometries) as unique environments for controlling flow within an evaporating droplet, which, in turn, regulates the well-ordered structure formation in one step. The proposed CAREER project is significant because it will lead to a new paradigm for creating hierarchically ordered structures on surfaces in a simple, controllable, and cost-effective manner (i.e., potentially transformative research) for potential applications in photonics, electronics, optoelectronics, biosensors, nanotechnology, and biotechnology. The outcomes from the research are thus expected to make significant contributions to the advancement of nanomaterials science. The broader impact of the proposed work includes stronger nanoscience and nanotechnology education across several levels. A new course on Nanostructured Polymeric Materials for senior undergraduate and junior graduate students will be developed. Female undergraduate students will be recruited for summer nanomaterials research from Iowa State University's Program for Women in Science and Engineering (PWSE), thus strengthening the involvement of an underrepresented group in the project. Summer workshops will be created for K-12 teachers who, in turn, will share the new information with their students. Web-based lesson plans on polymeric nanomaterials and nanocrystals will be developed by female high school interns for 5th-8th graders nationwide. This activity will ultimately expose elementary and middle school students to the nano-world. Knowledge generated by this CAREER project may lead to the creation of novel devices and materials that exhibit unique functions due to hierarchical arrangement of nanoscopic building blocks, thereby transitioning fundamental scientific discoveries into useful technologies that benefit society.