Cells in vivo respond to chemical and mechanical cues in the environment. In fact, it is the resulting migration of cells as a cohesive group that underlies embryonic morphogenesis, wound repair and cancer tumour development and invasion. Techniques have been developed to investigate chemotaxis, haptotaxis and mechanotaxis – the directional movement of cells in response to soluble chemical cues, substrate-bound chemical cues and mechanical cues respectively. Most of the existing tools however, have been designed for and applied to the investigation of single cell migration. Given its importance in vivo, there is a need for adapting these methods and applying them to characterize directed collective cell migration. The main objective of my thesis was to engineer tools and quantitative methods to investigate collective cell migration and use them to compare single and collective migration in response to mechanical cues and substrate-adhered chemical cues in vitro.

A computer-controlled microfluidic extensional flow device is developed for trapping and manipulating micron-sized hard and soft particles. The extensional flow is generated in a diamond-shaped cross-slot that has each corner connected to a pressure-controlled liquid reservoir. By employing an imaging-based control algorithm, a particle can be made to move to an arbitrary position within the slot by adjusting the reservoir pressures and hence the fluid flow rates into/out of the slot. Thus, a soft particle can be trapped indefinitely at a point within the slot, and a known hydrodynamic force can be applied to study the dynamics of stretching and breakup of the particle. Alternatively, adhesion or coalescence dynamics of soft particles may be investigated by effecting a controlled collision between two particles. The device is validated by measuring the low interfacial tension of a compatibilized oil-water interface.

Stroke is a leading cause of disability in the world, for which there currently is no effective treatment. One potential method for treating stroke is to stimulate the endogenous neural stem/progenitor cells (NSPCs) in the subventricular zone (SVZ) of adult brain to replace the tissue lost during stroke. Two growth factors that have shown promise in eliciting functional repair in rodent models of stroke are epidermal growth factor (EGF) and erythropoietin (EPO). However, there is a significant challenge in delivering protein drugs in a minimally invasive yet effective manner. In this thesis, a minimally invasive polymer-based system is developed to control the sequential release of EGF followed by EPO. This system comprises of a hyaluronan-methylcellulose (HAMC) hydrogel and two types of polymeric particles, and is applied epicortically to deliver EGF and EPO to stroke-injured mouse brains in a minimally invasive manner. In this thesis, the following are demonstrated: 1) The ability of therapeutics delivered locally to reach the target site after delivery is crucial for the success of local delivery strategies. PEG-modification leads to enhanced penetration distance of EGF. 2) When delivered epicortically to the stroke-injured mouse brain using HAMC, PEG-EGF penetrates further into the brain compared to unmodified EGF. Both EGF and PEG-EGF stimulated NSPC proliferation in the SVZ, but the extent of stimulation is greater when PEG-EGF is delivered compared to unmodified EGF. 3) The transport of EPO is similar in the uninjured and the stroke-injured brain following epicortical delivery from HAMC. EPO delivered epicortically from HAMC is able to reach the SVZ and can enhance neurogenesis in the stroke-injured brain. 4) A composite delivery system is engineered where PEG-EGF and EPO are individually encapsulated in different polymeric particles, and the particles are embedded in the HAMC hydrogel matrix. Stroke-injured animals that receive composite-mediated growth factor treatments ultimately achieve repair comparable to that achieved using a conventional catheter/osmotic minipump infusion system, without causing tissue damage associated with insertion of the infusion system into the brain.

ACPEL devices were fabricated onto various paper substrates. The dielectric and phosphor layers were mask printed, a PEDOT:PSS/SWCNT ink was inkjet-printed for the cathode and a translucent conductor was applied with a paintbrush for the anode resulting in a maximum luminance of 8.05 cd/m2 at 300 VAC and 60 Hz. It was found that the conductivity of the PEDOT:PSS/SWCNT ink on the various paper types was affected by the coating and paper thickness. Novel ACPEL devices were also fabricated by incorporating paper as the dielectric layer of the device. The maximum luminance achieved was 7.24 cd/m2 at 300 VAC and 60 Hz. It is shown that the dielectric constant of the paper and hence the performance of the resulting EL device may be enhanced by filling the sheet with BaTiO3 and by the surface treatment of the sheet.

ACPEL devices were fabricated onto various paper substrates. The dielectric and phosphor layers were mask printed, a PEDOT:PSS/SWCNT ink was inkjet-printed for the cathode and a translucent conductor was applied with a paintbrush for the anode resulting in a maximum luminance of 8.05 cd/m2 at 300 VAC and 60 Hz. It was found that the conductivity of the PEDOT:PSS/SWCNT ink on the various paper types was affected by the coating and paper thickness. Novel ACPEL devices were also fabricated by incorporating paper as the dielectric layer of the device. The maximum luminance achieved was 7.24 cd/m2 at 300 VAC and 60 Hz. It is shown that the dielectric constant of the paper and hence the performance of the resulting EL device may be enhanced by filling the sheet with BaTiO3 and by the surface treatment of the sheet.

Perchloroethene and trichloroethene are among the most persistent groundwater pollutants, and Dehalococcoides is the only known species that can degrade these compounds completely to non-toxic ethene. Characterization of the reductive dehalogenase (RDase) enzymes responsible for dechlorination is important to understanding this process. A series of dechlorination assays were performed with whole cell suspensions and cell-free extracts of three Dehalococcoides-containing mixed microbial consortia to compare dechlorination kinetics and to characterize co-contaminant inhibition. Michaelis-Menten kinetic parameters Vmax and Km, as well as non-competitive inhibition coefficients for 1,1,1-trichloroethane and 1,1-dichloroethane inhibitors are reported. Secondly, blue native gel electrophoresis was developed as a method to isolate active protein complexes containing RDases. Thirdly, sources of variability in the isotopic fractionation of vinyl chloride to ethene reaction step were examined using cell-free extracts and whole-cell suspensions. Understanding the function and range of RDases are goals towards the successful application of Dehalococcoides-containing cultures to remediate contaminated sites.

Stress corrosion cracking (SCC) susceptibility of the phosphorus de-oxidized copper has been evaluated in synthetic seawater polluted by sulfides using slow strain rate test (SSRT). The effect of concentration of sulfide, temperature, and applied cathodic and anodic potentials on the final strain values and maximum stress were also studied. No cracks were found under the tested conditions. The final strain and maximum stress values decreased but not significantly, with increase in the temperature, applied anodic potential and sulfide concentration. The observed effect is due to the section reduction by uniform corrosion. Lateral cross section and microscopic examination of the fractured specimen ruled out the existence of the localized corrosion. Electrochemical measurements showed that the Cu2S film is not a protective film and also exhibits a mass transfer limitation to the inward diffusion of the sulfides. Based on these results the reasons for the absence of cracking are also discussed.

Salt iodization is widely available throughout the developing world. Incorporating other micronutrients into the existing salt iodization process could prevent multiple deficiencies. The thesis objective was to develop a stable formulation of salt dual fortified with folic acid and iodine, using a single solution that could be sprayed on. The micronutrients needed to be fully solubilized and stable in solution for at least one month. In the absence of an alkaline environment or antioxidant, iodine losses occur most likely due to the oxidation of folic acid by potassium iodate. Optimal salt formulations were prepared by spraying a pH 9 carbonate-bicarbonate buffer solution containing folic acid and iodine dissolved at 0.35% (w/v) each. Acceptable micronutrient retentions of > 90% were observed in refined salt after 6 months of storage at 45°C/60% relative humidity. Further investigations into increasing the concentration of iodine and folic acid in the spray solution are recommended.

Turbulence is a significant factor in near-road air quality, as it affects the initial dilution, dispersion, and the ultimate fate of pollutants. This study used computational fluid dynamics simulations to model the turbulent kinetic energy (TKE) on roadways, focusing on vehicle-induced turbulence. TKE was shown to decay with different power-law exponents depending on vehicle types; vehicle speeds and winds affect TKE; and thermal impacts are negligible. It was found that TKE is superimposed for vehicles in series; TKE does not dissipate far laterally, and the side-by-side interactions are not significant regardless of the directions. Thus, TKE for different traffic compositions may be expressed as a sum of the contribution from each type of vehicle. Insights gained in this study may enable the quantification of TKE for various traffic scenarios based on TKE values of single vehicle of different types, and simplify the TKE estimations in regional air quality models.

Biogas, produced from anaerobic digestion of cattle manure, is an attractive alternative energy source as it is rich in methane. However, it is necessary to remove hydrogen sulfide from the biogas before it can be used in engines for electricity generation. Currently, large scale biogas systems employ physical adsorbing solvents to upgrade and purify biogas which is not economically feasible for small scale biogas systems. Activated carbon made from anaerobic digestate proves to be an effective adsorbent of hydrogen sulfide because it has minimal operating costs and essentially zero raw material cost. A model is developed to predict the adsorption capacity, carbon bed life span, and breakthrough time for this carbon material. By analyzing the reaction constant, adsorption constant, and degradation constant, adsorption behavior under different operating conditions were studied. The model can be scaled-up to model adsorption for biogas loading rates for small to large scale cattle farms.