RUI: Multi-scale modeling of interfacial flows of magnetic fluids with macro-chain aggregates

Magnetic fluids (or ferrofluids) are suspensions of magnetic nanoparticles whose properties and flows are affected by applied magnetic fields, making them useful in industrial and biomedical applications. Potential future applications, such as targeted drug delivery and micro fluidic pumping, involve both active interfaces and motion on small scales, upon which the magnetic particle distribution may become nonuniform. In particular, under moderate fields, nanoparticles aggregate into macroscopic chains which, in turn, affect the fluid flow. These chains have been previously observed by the investigators using high resolution X-ray phase-contrast images obtained at Argonne national lab. Further progress in modeling and simulation of ferrofluids on small scales demands new approaches. To speed the pace of development and design of ferrofluidic devices and to facilitate the exploration of new ferrofluid applications, a robust and exible simulation method is required. This project will develop, validate and apply such a tool, in the form of a multi-scale code for the numerical simulation of interfacial flows of magnetic fluids. These simulation codes will integrate a mesoscale model of field-induced macroscopic magnetic-particle chains and a realistic nonlinear magnetization for the bulk ferrofluid with a state-of-the-art interfacial Navier-Stokes code. The Navier-Stokes computation will include a high-order curvature algorithm that accurately computes surface tension at interfaces. Viscous stress due to field induced macro-chains will be derived from a dissipative particle dynamics type model. The proposal includes carefully planned projects that will involve and support students from Montclair State's diverse population in leading-edge research.

The investigators will develop a computer simulation of magnetic liquid, also known as ferrofluid, a unique 'smart' material that is easily manipulated using ordinary magnets. While widely used as a liquid seal in computer disk drives, this easily controlled fluid has far greater potential, including applications in biomedicine (drug delivery, eye surgery and as MRI contrast agents) and in small scale devices which manipulate tiny fluid volumes, as used in biotechnology and pharmaceuticals tests. Progress has been stalled by two obstacles. First, experiments are limited because the fluid is very opaque, appearing as a shiny black liquid. Second, the nano-scale particles which give the fluid its magnetic character also lead to internal structures, such as particle chains, which make its mathematical description complex. This project overcomes the first challenge by using state-of-the-art computer simulations instead of experiments, while it overcomes the second challenge by building simple mechanical models of internal structure based on high resolution x-ray experiments, performed at Argonne national lab. The investigators will involve students in key roles in the development of this computer simulation tool that can be used to explore, design and test these and other new applications of magnetic fluids.