Master of Science, University of Akron, 2016, Chemical Engineering

Poly (N-isopropylacrylamide) (pNIPAAm), a thermo-responsive polymer that exhibits a lower critical solution temperature (LCST) of 32 °C in water has found an extensive use in tissue engineering and bioengineering applications in general. Since it is soluble in water, one of the main challenges that limit its applications in an aqueous environment is the tedious and expensive electron beam or plasma based procedures to retain it on a substrate. In this study, we report the use of various types of organosilanes to form siloxane networks for immobilizing pNIPAAm onto Si-wafer and silica glass substrates in a simple two-step approach: spin coating followed by thermal curing. Attempts are made to elucidate the entrapment mechanism and factors that affect such entrapment. It was found that the entrapment occurs via the segregation of high surface tension organosilanes towards the substrate at a temperature higher than the glass transition temperature (Tg) of pNIPAAm and simultaneous cross-linking of the segregated organosilane molecules that form siloxane networks. Organosilanes having low surface tension were found to segregate towards the air-film interface leading to poor entrapment. Factors such as polarity and hydrogen bonding were found to influence the retention of those organosilanes in the blend film during spin-coating and thermal annealing and subsequent film retention after 3 days of soaking in cold water. Additionally, organosilanes that are allowed to hydrolyze and oligomerize in the blend solution prior to spin-coating also resulted in higher organosilane retention and subsequently, thicker retained blend films compared to solutions that were spin-coated immediately after preparation. Substrates utilizing those organosilanes to entrap pNIPAAm resulted in stable films that exhibited thermo-responsive behaviors that were verified by wettability measurements. Rapid cell sheet detachment (<5 min) of embryonic mouse fibroblast cells were obtained on all su (open full item for complete abstract)

Committee: Bi-min Zhang Newby Dr. (Advisor); Gang Cheng Dr. (Committee Member); Jie Zheng Dr. (Committee Member) Subjects: Biomedical Research; Chemical Engineering; Chemistry; Materials Science; Polymers

BS, Kent State University, 2014, College of Arts and Sciences / Department of Chemistry and Biochemistry

Biomaterials must adequately facilitate tissue fixation while maintaining mechanical properties. Surface rigidity and roughness have been shown to modulate soft tissue response. In order to improve soft tissue adhesion on rigid substrates, phase separation of organosilanes was employed to create self-assembled monolayers (SAMs) of tunable wettability by creating nano-size hydrophobic and hydrophilic domains capable of eliciting phenotypic response in skeletal myoblast cells. P-aminophenyltrimethoxysilane (APhMS) and octadecyltrichlorosilane (OTS) was varied in a binary solution in order to achieve SAMs with nanoislands. C2C12 skeletal myoblast cells were seeded onto prepared SAMs in order to investigate changes in cell behavior due to surface interactions. Hydrophilic SAMs were observed to enhance cell spreading, viability, and myotube formation on glass surfaces. Furthermore, 5:5 APhMS: OTS was found to increase myoblast differentiation and anisotropy through cell mechanosensing of nanoislands. Virtual roughness of 5:5 APhMS:OTS was created by nanosized methyl-terminated pillars in an amine-terminated matrix.

Committee: Christopher Malcuit Ph.D. (Advisor); Grant McGimpsey Ph.D. (Committee Member); Edgar Kooijman Ph.D. (Committee Member); Paul Sampson Ph.D. (Committee Member) Subjects: Cellular Biology; Chemistry

Doctor of Philosophy, University of Akron, 2008, Chemical Engineering

Water droplet movements on a variety of organosilane modified wettability gradient surfaces were first examined. These gradient surfaces were generated by the contact printing (CP) of octadecyltrichlorosilane (OTS) or octadecylmethyldichlorosilane (OMDS) on silicon wafer surfaces. The experimental results showed that a water droplet as small as a few pecoliters could move toward the higher wettability region on these gradient surfaces. As the droplet size or the gradient scale increased, the droplet velocity increased. The study also confirmed that of the two factors to cause the resistances in droplet movement, contact angle hysteresis (CAH) was always the predominated factor, while the interfacial friction only became more important when the wettability gradient size scaled down to sub-millimeters.To predict the contribution of CAH and interfacial friction in resisting droplet motion, the modes of droplet movement on the gradient surfaces should first be determined. However, under the current experimental conditions (small droplets and short droplet traveling time); it was too challenging to obtain the droplet motion modes on the wettability gradient surface. Alternatively, tracer particles were suspended in large water drops that moved down on inclined OTS surfaces, also generated by CP, and the internal fluidity was deduced from the movement of the tracer particles. The results showed that the motion of the water droplet is a combination of sliding, slipping, and rolling. Furthermore, to evaluate the effect of drop size on the drop motion mode, water drop movements on an inclined dimethydichlorosilane (DDS) surface having a low water CAH (i.e. CAH of about 5° as compared to ~ 20° for OTS or OMDS surfaces) were studied. It was experimentally observed, by including tracer particles inside the water drops during the drop movements, which at a lower inclined angle, rolling had a greater contribution to the drop motion; while at a higher inclined angle, sliding con (open full item for complete abstract)

Committee: Bi-min Zhang Newby PhD (Advisor); Steven Chuang PhD (Committee Member); Edward Evans PhD (Committee Member); Jun Hu PhD (Committee Member); Rex Ramsier PhD (Committee Member); Igor Tsukerman PhD (Committee Member) Subjects: Chemical Engineering