NIRT: Nanoscale Directed Self-Assembly in Electrical and Optical Fields

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ABSTRACT - 0506701University of DelawareFabricating nanostructured materials or nanoscale devices will most certainly employ selfassembly. In particular, solution-phase self-assembly, which is the biological route to creating functional nanostructures, promises scientifically and economically viable ways to develop industrial nanotechnology. Engineering micro-to-nanoscale devices and nanostructured materials requires control and understanding of the thermodynamics and kinetics of self-assembly of nanoscale "building blocks" in solution. This process is hierarchical in nature, so that molecular-level physics and chemistry lead to interaction potentials between nanoparticles and solvent molecules, which under the right conditions can assemble into higher-order structures on the nano-to-micron scale with emergent functionality. However, to harness self-assembly for man-made applications a high level of direction and control are required. We propose an integrated scientific and educational program to develop novel routes using directed selfassembly to manufacture nanoscale devices and advance the state of knowledge in the field of nanoscale manufacturing, including both rapid dissemination of our results and broader nanotechnology training.Directed self-assembly is the application of external fields (i.e., electric, optical, and flow) to bias or modulate thermodynamic and mechanical driving forces in order to assemble large numbers of particles in parallel with high selectivity and precision. To advance this technology, we have created a partnership of five researchers from three universities who have complementary talents and skills that, in combination, can develop new and valuable approaches to understand and control the interactions between colloidal & nanometer scale "building blocks", and then to manipulate those objects to form useful structures, devices, and prototypical nanoscale manufacturing schemes. Specifically, we propose a research program primarily designed to address the need to understand and control atomic and molecular interactions in nanoparticles and molecular assemblies to manufacture novel self-assembled microstructures with higher levels of functionality. Experimental techniques capable of controlling molecular-to-micron scale structure and dynamics will be developed, along with complementary theoretical modeling and simulations.The intellectual merit of our proposed research revolves around our integration of experiment, simulation, and theory to further develop and rigorously test fundamental understanding of directed self assembly at the nanoscale. For example, we propose specific experiments whereby patterned arrays of a few, model colloids will be held by optical tweezers while exposed to dielectrophoretic forces (ac electric fields). Parameter-free Stokesian Dynamics simulations will be compared on a particle-by-particle basis to test our understanding of the many-body electrostatic and hydrodynamic forces underlying dielectrophoretic directed assembly, thereby advancing our knowledge about the fundamental properties and processes that enable externally controlled assembly. The use of directing optical tweezers will enable direct measurements of the static and dynamic interactions between particles, providing powerful new particle characterization methods. Simulation, theory and experiment will drive toward the goal of assembling ever finer building blocks such that the methods can be applied to nanoparticles, and perhaps, even to proteins. Results of these investigations should facilitate the rational design, control, and optimization of manufacturing processes based on directed self-assembly, as well as the synthesis of new materials, such as photonic materials, nanoporous membranes, and biosensors. This work offers the potential for high reward because triggering, directing, and controlling the massively parallel, but highly selective assembly of nanoscale particles in solution or on to surfaces can create truly functional materials from colloid, macromolecular and nanoparticle building blocks of engineering significance.Additional broader impacts of our work include the development of educational tools, workshops, and short courses. Short courses on particle science and nanoscale manufacturing techniques will be offered to students as well as to industrial researchers, along with new web-based teaching modules about directed self-assembly. The collaboration proposed herein also provides unique training for doctoral and undergraduate students to work in the field of nanotechnology, providing them with skills and background for rational, hierarchical design and fabrication. The outcome of the research will be primarily focused on enabling skills and techniques that can be used across a wide array of industries. An industrial partnership is proposed to facilitate the research and its practical applications.This proposal addresses the themes of Nanoscale Structures, Novel Phenomena, and QuantumControl and Multi-scale, Multi-phenomena Theory, Modeling and Simulation at the Nanoscale.