(7hx) Spin-Segregation of Active Spinners

Farhadi, S. - Presenter, University of Pennsylvania
Arratia, P. E., University of Pennsylvania
Durian, D. J., University of Pennsylvania
Research Interests:

In the following, I briefly explain the projects I am currently involved as postdoctoral researcher, and my past studies as a graduate student:

Postdoctoral Research:

(i) Reversibility of a Colloidal System (Prof. Arratia's lab): I am currently studying a colloidal system adsorbed at an oil-water interface, which is subject to cyclic shear. The colloidal particles are sub-micron size, such that Brownian motion has significant contribution to the single particle dynamics. Through this study, we found that thermal noise significantly affects the reversibility of material in a nontrivial manner.

(ii) Predicting Reversible Rearrangements by Machine Learning Techniques (Collaboration with Prof. Liu and Prof. Yodh): Through this study, I am interested in finding the structural signatures which determine the dynamics (here, reversibility of cycles). This turns out to be a very challenging problem for disordered materials, and remains as an active research area. We have recently developed techniques based on machine learning to predict the reversibility dynamics based on the structure of a disordered matter.

(iii) Dynamics of Active Systems (Prof. Durian's lab): In active particulate systems, in contrast to passive systems, single particle dynamics is independently present even without external driving. We have designed two species of active granular systems: spinners, and translators. The intra-structure of particles (which are 3D printed) is designed such that they either spin or translate in the presence of an upward air flow. In this ongoing study, we aim at describing the collective dynamics, and in particular, we search for an effective temperature which governs the dynamics. Subsequently, we will be able to extract an equation of state for these systems.

PhD Research:

My PhD research was an experimental study on the jamming and rheology of granular materials (Prof. Behringer's lab), with a specific focus on elliptical-shaped particles. I performed continuous Couette shear (rheology) and cyclic compression (jamming-unjamming) on both systems of circular and elliptical shaped particles. The identical experiment, on both circles and ellipses, enabled us to understand the role of particle anisotropy on jamming and the bulk rheology.

Teaching Interests:

My teaching experience during graduate studies involved teaching lab sessions, and helping students with their homeworks, as well as the opportunity of teaching a full course (Introductory Electricity, Magnetism, and Optics) as an instructor. Even though my graduate studies were in the field of Physics, however, I have a BSc. degree in Chemical Engineering, which provides me sufficient tools and familiarity with subject matter, to teach undergrad engineering courses.