Dissertation Defense – Ren Geryak
Dr. Vladimir Tsukruk, Advisor, MSE
Dr. Dong Qin, MSE
Dr. Meisha Shofner, MSE
Dr. Andrei Fedorov, ME
Dr. Nancy Kelley-Loughnane, AFRL
"Responsive Nanostructures for Controlled Alteration of Interfacial Properties"
Responsive materials are a class of materials that are capable of “intelligently” changing properties upon exposure to a stimulus. These materials can be created in such a way to change stiffness, adhesion, morphology, permeability and many other interfacial behaviors. In turn, these behaviors can be driven by a wide range of stimuli including chemical gradients, pH, mechanical stresses, electromagnetic fields, and temperature. While such materials are ubiquitous in nature, artificial assemblies of materials do not meet the requirements of biocompatibility combined with rapid, large-scale, and reversible changes in materials properties to create truly biomimetic systems. Silk ionomers are a promising candidate of biopolymers that combine the robust, biocompatible properties of silk fibroin with the responsive properties of poly-l-lysine and poly-l-glutamic acid. These polypeptides can be assembled using the well-known technique of layer-by-layer processing, allowing for the creation of finely tuned nanoscale multilayers coatings, but their properties remain largely unexplored in the literature.
This research explores the properties of silk ionomer multilayers assembled in different geometries, ranging from planar films to three-dimensional microcapsules. This work studies the mechanical and interfacial properties of simple multilayers of silk ionomers using atomic force microscopy based testing. This leads to the development of responsive microcapsules that have highly pH dependent stiffness and permeability as well as the creation of reversible, self-rolling photopatterned microarrays. Finally, the research concludes with a discussion of complex systems that allow for chemical responsive fluorescence or magnetically responsive light scattering.