Theoretical and Numerical Study of Magnetic Non-Spherical Particles in a Shear Flow Subjected to a Uniform Magnetic Field

Dr. Christopher Sobecki CSED ORNL Seminar Speaker
Dr. Christopher Sobecki
Sandia National Laboratories

Abstract:  Magnetic manipulation of non-spherical magnetic microparticles is important for applications in shape-based and magnetic-based separations such as waste management, disease diagnostics, drug delivery, and mining. Manipulations of magnetic microparticles also include chain formation to assemble compositions for electronics, drug loading designs, and magnetorheological fluids for smart armors, hydraulic brakes, and dampers.
In microfluidic devices, separation-formation-effectiveness depends on the shape of the channel, the shear rate, and the magnetic field strength and direction. Accurate prediction of particle separation and chain formation involve highly complex and computational expense-demanding studies in microfluidic devices, magnetic fields, and particle-particle/wall interactions.
This research included experimental, theoretical, and numerical studies for the dynamics of magnetic particles. The first study analyzed the rotational dynamics of paramagnetic and ferromagnetic particles in a simple shear flow and under a uniform magnetic field, as well as a numerical application in a Couette flow. In the second study, further theoretical analyses were conducted for a three-dimensional rotation of both magnetic types. A paramagnetic particle was placed in a curved channel and under a uniform magnetic field in the third study. Finally, a two-dimensional investigation on the dynamics of two Janus particles under a uniform magnetic field and in a simple shear flow was the focus of the fourth study.
In this research, the theoretical and numerical investigations addressed how various magnetic properties and particle shapes reacted in different conditions, e.g. magnetic field strength, direction, simple shear, and channel flows. These studies provided insights on the rotation and migration behavior of micro-sized ellipsoidal and Janus particles in straight channels, curved channels, and shear flows. This research supports current and future studies in biomedical and industrial applications.
Bio:     Christopher Alan Sobecki received a B.S in Mathematics, with a concentration in computer science and astrophysics, as well as a Minor in Dutch Language and Culture Studies in May 2015 from Indiana University, Bloomington, Indiana, USA. In 2016, he studied Statics, Thermodynamics, and Engineering Design (Capstone Engineering Design) as a non-degree student at Indiana-University-Purdue-University-Indianapolis (IUPUI), Indianapolis, Indiana, USA. In March 2021, he successfully defended his dissertation at Missouri University of Science and Technology (MS&T), Rolla, Missouri, USA and is expected to graduate in May 2021 with his PhD in Mechanical Engineering. His research interests include fluid dynamics, computational fluid dynamics, numerical studies using computer software (MATLAB, Python, Linux), micro/nanofluidics, magnetism, mathematical analysis, lab-on-a-chip, simulations (COMSOL and LAMMPS), magnetism, molecular dynamics, and medical/defense/energy applications.
During his Ph.D. studies, Christopher was awarded the Chancellor Distinguished Fellowship (in 2016) as well as Koerner Family Foundation Stipend (in 2021) and worked as a graduate research assistant under Dr. Cheng Wang.  His work included the dynamics of paramagnetic and ferromagnetic particles in shear flows and under uniform magnetic fields (both in two- and three-dimensions), particle transportation in a curved channel, and the dynamics of spherical magnetic Janus particles in shear flows and under uniform magnetic fields.  His current research includes a collaborative effort with the chemistry department to fabricate silver layers on DNA origami.
Christopher mentored three undergraduate students while they fabricated disc and ellipsoidal particles, as well as electromagnetic Helmholtz coils. Additionally, he graded and led laboratory assignments for ME 3131 Thermofluid Mechanics and was a graduate teaching assistant for ME 4761 Engineering Design (senior-level) for International PROOF Systems, LLC (primary coordinator) along with Clear Horizon, LLC (secondary coordinator).  
He volunteered at MS&T as a laboratory instructor for middle school aged girls and other underrepresented groups in engineering.
Using the benefits of the Chancellor Distinguished Fellowship, Christopher presented his research at the American Physics Society (APS) at the 70th-73rd Annual Division of Fluid Dynamics Meetings from 2017 to 2020 in Denver, Atlanta, Seattle, and Chicago, USA.  He also presented his work at a graduate seminar presentation hosted by IUPUI in 2017. He exhibited his research by conducting poster presentations from 2017 to 2020 at MS&T.
During his Ph.D. study, he authored and co-authored six journal papers and ten conference abstracts/papers/posters/presentations.  He currently is a year-round intern at Sandia National Laboratories, working remotely in Rolla, Missouri, developing models to study the thermodynamic properties of water molecules during a liquid-vapor phase change.

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Last Updated: March 24, 2021 - 9:12 am