Computational modeling of fluid-solid interfaces at the macroscale has long since crossed the boundary of pure academic interest to become an essential tool for industry. Sectors such as aerospace, automotive, medical, and chemical manufacturing routinely design, test, and optimize their products using one of the many inexpensive software packages that are now available. Unfortunately, these macroscale methodologies are not applicable at the nanoscale. The forces dominating the fluid-solid interfacial processes at the nanoscale are quite different and more complex than those at the macroscale. The ability to model such nanoscale interactions could find broad use in nanotechnology, biotechnology, and materials science, three of the primary areas of Federal strategic interest. Understanding, for example, how the size of some types of nanoparticles affect their reactivity with fluidic environments can lead to the production of significantly more effective materials for energy storage and conversion (batteries). The goal of this project is to develop mathematical models capable of describing nanoscale fluid-solid interfaces, culminating in the development of open-source software for general-purpose simulations of nanoscale motion and energy transfer. Similar to macroscale systems, where automotive engineers, for instance, use software packages to design cars, it is expected that this project will grow to become an essential computational design tool for nanoscale motion that will help scientists create nanomachines capable of delivering drugs to pathogenic cells, for example.
This research project aims to develop a multiscale-multiphysics methodology to simulate nanoscale fluid-solid interfacial processes and their effects on nanoscale motion. The specific objectives of the project are: (1) The development of a novel field-particle methodology, which will concurrently describe three of the most dominant forces at the nanoscale: thermal fluctuations, viscosity, and surface tension. With this approach, structures and fluctuating fluid are coupled directly through excluded volume effects and hydrodynamic forces without the imposition of boundary conditions. (2) The coupling of first-principles kinetic Monte Carlo methods with fluctuating hydrodynamics to describe nanoscale energy transduction and transfer from heterogeneous catalytic surfaces to the surrounding fluid environment. (3) To overcome computational efficiency challenges typically present in multiscale multi-domain approaches by the integration of algorithms in a large-scale parallel code for nanoscale computational fluid dynamics. This method will be applied to study how energy released from catalytic nanostructures can be utilized to achieve controlled nanoscale motion. Although the primary focus of this research is controlled nanoscale motion, the algorithms and software developed are expected to have an important multidisciplinary impact to other topics, such as nanocatalysis and drug delivery. The method developed in this project will be transformative to current fluid-solid interaction methodologies since it makes the realization of active and dynamic interfacial processes possible without the implementation of boundary conditions or computationally expensive techniques for tracking interfaces. Hydrophobic forces, wetting-dewetting phenomena, stochastic electrokinetics, and other out-of-thermodynamic equilibrium transfer processes between solids and fluids will be incorporated into traditional computational fluid dynamics (CFD) methodologies. The research results will be a rational extension of CFD to the nanoscale where interfacial and stochastic processes cannot be ignored. The large-scale parallel software for nanoscale motion will be released to the scientific community and is expected to help pave the way toward advanced computer-based approaches for designing moving nano structures.
