Controlling nano-structure formation by hydrodynamic instability
Abstract
This project seeks to elucidate new aspects of complex fluids confined as nanometer-scale films. Through engineering of rheological and thermal properties of fluids by small solid solutes (called ÒnanofluidsÓ), we aim to control pattern formations in thin fluid films, as a new approach for material fabrications. Nanofluids, which are dilute colloidal solutions of nanometric particle, or nanoparticle (comprising inorganic core particle and shell of organic ligands), hold promise in controlling viscosity, surface tension, and thermal conductivity. Prior experimental investigations of nanofluids have been compromised by the use of nonuniformly-sized solutes, making the comparison with theory less accurate. On the other hand, chemical syntheses of uniformly-sized nano-materials are available, including the protocols developed by the PI. This project will bridge the gap between nanofluid research and nano-materials synthesis, and will synergize towards a more precise and systematic engineering of the fundamental properties of nanofluids. In addition to size-controlled nanoparticles, we will synthesize new sub-nanometric particles to evaluate nanofluids properties with systematic and precise variation of solute size from <1 nm to ~100 nm. Preliminary results indicate a surprisingly large effect on fluid properties with sub-nanometric particles in nanofluids. We will characterize the dependence of the rheological and thermal properties nanofluid properties on solute material, size, ligand, and concentration. Our goal is to engineer thermal and rheological properties of nanofluids to understand and control hydrodynamic instabilities in nanofluids, toward a new strategy for fabrication of patterned surfaces that are difficult to achieve by conventional top-down (lithography) or bottom-up (self-assembly) approaches. We preliminarily discovered that aggregation and coalescence of sub-nanometric particles in heated thin fluid films (hence involving thermal conductivity, viscosity, and surface tension) enable systematic formation of nano-structured surface, controlled by the nanofluid film thickness and the substrate temperature. Discrete molecular nature of nanofluids containing sub-nanometric particles, confined within <100 nm-thin geometries, may reveal a dynamics delineated from continuum analytical theories. Fundamental understanding of the principles underlying the emergence of order in nanofluids will improve our ability to design functional surfaces systematically.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 09, 2020
- Source ID
- W911NF2010176
Entities
People
- Shunji Egusa
Organizations
- Army Contracting Command
- United States Army
- University of North Carolina at Chapel Hill