NER: Integrated Magnetic and Chemical Assembly Techniques for Building Nanoparticle Arrays

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This Nanoscale Exploratory Research (NER) project aims to develop fluidic self-assembly strategies (via magnetic and chemical forces) to build arrays of metal nanoparticles on transparent substrates, serving as a low-cost, high-throughput solution for fabricating chip-based surface plasmon resonance (SPR) biosensors. The key concept employed in this work is that nonmagnetic materials, such as gold nanoparticles, can be manipulated inside a magnetizable fluid, such as ferrofluid (e.g. a fluid concentrated with magnetic nanoparticles). When an external field is applied to the fluid, the gold nanoparticles become negatively magnetized with respect to the surrounding medium, and as a result of dipole-dipole interactions, the gold nanoparticles will form well-ordered nanoparticle configurations with tunable periodicity. Once assembled into an array, chemical reactions initiated between the particle and substrate can embed the array structure on the surface even after rinsing of the ferrofluid. The intellectual merit lies in studying a relatively unexplored topic of manipulating nonmagnetic nanoparticles inside magnetic fluids. The major intellectual challenge is to develop computational methods for self-consistently calculating the magnetic field, resulting from magnetic nanoparticle concentration gradients and interactions with the substrate. The PI will encourage participation of undergraduate and graduate students in research as well as through the development of new courses in classical electricity and magnetism as defined in the context of the broader fields of self-assembly and nano-manipulation. Special emphasis will be placed on recruiting undergraduate students from a Historically Black College and University (HBCUs) or Historically Minority University (HMUs), and through the Duke University Pratt Fellows program.