(3ct) Polymer Networks: Modeling and Emerging Applications

We develop a particle-based computational model to explicitly simulate the mechanics and transport properties of polymer gels, i.e. cross-linked polymer networks immersed in Newtonian fluids. Our hybrid numerical approach consists of a bond-bending lattice spring model to capture the micromechanics of random networks of interconnected elastic filaments and the dissipative particle dynamics to explicitly model the viscous fluid and diffusive objects. We use our mesoscale model to examine how permeability and diffusivity of gels change when they undergo mechanical deformations and establish the dependence of the transport properties on the variation of the network structure under stretching and shear loads. We also employ the model to examine mechanisms for controlled release of nanoparticles enclosed within microgel capsules. We show that the capsule swelling results in a steady particle release, with a relatively slow release rate that is set by the diffusion through the network. We also demonstrate that the fluid flow though the capsule’s membrane during deswelling leads to a rapid particle release. This release, however, is limited as network mesh size decreases when capsule shrinks. To enhance the rapid release from the deswelling capsule, we introduce solid microstructures, e.g. rigid microrods, inside the capsule. The length of the rods is comparable to the capsule internal diameter and the rod radius is comparable to the size of nanoparticles. The rods stretch the membrane of deswelled capsule and promote formation of larger pores, which allow rapid and massive release of nanoparticles. Our findings reveal a new approach for regulating the release from micro-carriers by controllably changing the pore size. Furthermore, our three dimensional fully-coupled model of the cross-linked polymer networks provides a foundation for future studies of a broad range of problems in engineering, medicine, and biology that involve active and responsive polymer gels.

Bio:

I am a Ph.D. candidate in Mechanical Engineering at the Georgia Institute of Technology, and expect to receive my degree by June 2012. I received my B.S. degree with Highest Honors in Aerospace Engineering from the Sharif University of Technology (Tehran, Iran) in 2006. Subsequently, I joined the State University of New York at Buffalo where I earned my M.S. degree in Mechanical Engineering in 2009.

I have developed very broad research interests in fluid mechanics as well as soft matter physics and biomimetic design. During my Masters studies, I derived exact analytical solutions to study the flow field and particle deposition inside an evaporating colloidal drop. The focus of my Ph.D. research has been on the application of computational methods to a wide variety of problems involving interaction between deformable/rigid objects and their surrounding fluid. The problems I have considered range from the aerodynamics of flexible flapping wings and transport in random polymer networks to dynamics of fluid-filled microcapsules and colloidal flow in geometrically patterned microchannels. My high quality research has so far resulted in a book chapter and more than seven invited and regular articles published in leading archival journals and/or presented at major international conferences of the field. My works have also been highlighted in the National Science Foundation News and Georgia Tech Research Horizon Magazine, selected as a finalist for the Padden Award for Excellence in Polymer Physics Research, and featured in the Virtual Journal of Nanoscale Science & Technology. For more detailed information, please see my enclosed summary of research accomplishments. In the future, I plan to apply my expertise in fluid mechanics, mathematics, and soft matter physics to solve state-of-the-art problems in engineering and biology. Specifically, I am interested in computational design of adaptive and responsive soft materials.

In parallel with performing research, I have participated in writing several grant proposals for NSF, DOE and AFOSR, and served as a peer-reviewer for more than a dozen professional journals in my fields of interest. I have also paid equal attention to improvement of my teaching ability by taking teaching practicum course, delivering several lectures for two graduate courses, and teaching recitation and lab sections for three undergraduate courses. Therefore, given my academic background, I feel comfortable teaching undergraduate courses in Thermal/Fluid Science and graduate courses in Fluid Mechanics, Conduction and Convection Heat Transfer, Combustion, and Advanced Numerical Methods. Moreover, I have developed my mentoring skills by supervising several undergraduate research students at Georgia Tech.