The objective of this dissertation was to develop novel methods of patterning inorganic and organic materials, develop biocompatibility evaluations, and subsequently apply these methods toward developing biosensors and lab-on-a-chip devices, such as Interdigitated Electrodes (IDEs) and Microelectrode Arrays (MEAs) on non-traditional (such as nanostructured and plasmonic) polymer substrates or deploy these methods to enhance precision cellular placement on traditional (glass) MEA substrates. It was hypothesized that a combination of such facile microfabrication techniques and patterning technologies on traditional and non-traditional substrates would increase the sensitivity and selectivity of such sensor platforms by several orders of magnitude, and potentially introduce new modalities for cell-based biosensing. In order to demonstrate the biological functionality of these new IDEs and MEAs, a variety of cell cultures were used (cardiac, stem cell, and endothelial cells) to study the growth, proliferation, modes of increasing sensitivity and response to various compounds in vitro (outside the body).

Ultrashort-pulsed lasers have been used for high precision processing of a wide range of materials including dielectrics, semiconductors, metals, and polymers/polymer composites, enabling numerous applications ranging from micromachining, photonics to life sciences. However, there are challenges when applying this technology in the industry, which requires scale and throughput different from lab use. The goal of this research is to understand how ultrafast laser pulses interact with thin polymers/polymer composite materials and develop a method that is efficient for ultrafast laser processing of these materials. It is a common practice in industrial applications to run the laser at a high repetition rate and hence high average power. However, the heat accumulation under such processing conditions will deteriorate the processing quality, especially for polymers, which typically have a low melting temperature. An analytical solution for two-dimensional modeling of the temperature distribution has been presented and the solution is used to understand the effect of laser parameters on ultrafast laser processing of polypropylene (PP), which is an important polymer for both scientific and industrial applications. Laser cutting experiments are carried out on PP sheets to correlate with the theoretical calculation. This study shows that in laser cutting, the total energy absorbed in the material and the intensity are two important figures of merit to predict the cutting performance. It is found that heat accumulation can be avoided by a proper choice of the processing conditions and the optical properties (i.e. reflectance, transmittance, and absorptance) are important parameters to control processing with ultrafast lasers. To determine the reflectance, transmittance, and absorptance, time-resolved, single-shot measurements are performed in ultrafast laser interaction with polypropylene for a wide range of laser pulse energies. The absorptance during the ultrafast laser interaction with polymers is divided into the different linear and non-linear effective absorption channels and the absorption mechanism of ultrafast laser interaction with polymers in near-infrared wavelength are explained with a model that takes into account different effective absorption channels and suggests that the non-linear absorption originates from vibrational overtone/combination absorption. The enhancement of the absorptance has been investigated for efficiently processing thin polymers with ultrafast lasers by changing pulse duration. It is suggested from this study that the intense shorter pulse (167 fs) is more efficient for surface processing as most of the energy absorbed at the surface due to the strong nonlinear absorption, while a longer pulse (1000 fs) is more efficient for bulk processing for polymers. The results are useful for designing and controlling ultrafast laser processing of polymers and optimizing laser process parameters for the most efficient processing of polymers.

Controlling the morphology of thin films is key in optimizing the efficiency of polymer-based photovoltaic (PV) devices. The morphology and interfacial behavior of the multicomponent active layers confined between electrodes are strongly influenced by the preparation conditions. Results obtained in this work quantitatively show the photovoltaic device performance is strongly affected by the nanoscopic morphology, crystal orientation, composition distribution and the interdiffusion behavior of the photoactive layer. To better understand the physics of the photoactive layer in the organic photovoltaic devices, it is necessary to gain a quantitative understanding of the morphology and the manner in which it develops. A key element in the kinetics associated with the structure development is the interdiffusion of the components. To that end we used poly(3-hexylthiophene) (P3HT) / [6,6]-phenyl C61- butyric acid methyl ester (PCBM) bilayers as a model to investigate the interdiffusion of the components and its role in the development of the morphology. A detailed description of the diffusion behavior and the morphology developed from a layer of P3HT in contact with a layer of PCBM during thermal annealing is given. Amorphous P3HT and PCBM are shown to be highly miscible and PCBM can penetrate into the P3HT layer through the P3HT amorphous region and form the bulk heterojunction structure within a few second of annealing at 150 oC. The results indicated that one phase is a pure P3HT crystal domain and the other phase is the mixture of amorphous P3HT and PCBM, which is not consistent with a phase separation of the components by a spinodal decomposition mechanism. We put forth an alternative mechanism, namely a competitive crystallization/diffusion argument, to describe the origin of the morphology. These findings provide new insights and guidance in the generation of active layers in organic photovoltaics that are crucial in enhancing the device performance. Textured organic solar cells were also studied, providing another route to fabricate higher performance devices.

Protective coatings is used to enhance the corrosion resistance of buried pipelines. However, the effectiveness of epoxy-coatings may be compromised due to inadvertent presence of surface damage and coating disbondment. Additionally, the disbonded coated panels is expected to be less effective than that of scratched or un-defected panels. This research was designed to evaluate the coating performance of FBE and hybrid epoxy in simulated Arabian Gulf water and synthetic Sabkha. The influence of coating damage and disbondment on corrosion resistance was also investigated. Results of this research indicated a reduction in the adhesion bond between the coatings and substrate. The electrochemical impedance measurements demonstrated the need for an appropriate interpretation of results when this technique is used. The corrosion current density measurements indicated that both media are corrosive. Protective coatings under investigation did not show any blistering effect, loss of adhesion or color change under test conditions, thus reflecting their excellent corrosion resistance property.

<p>Nanomaterials have been heavily studied in the past two decades. Previous findings have demonstrated that the characteristics of nanocomposites and the performance of nanomaterial-based devices are both determined by the interfacial characteristics of the nanomaterials. However, there are still some remaining challenges from interfacial characteristics to device applications, which are specified as follows: the difficulty in identifying the interfacial contacts of nanostructured surfaces, the instability of nanocomposite surfaces, and the under-researched mechanism of the correlation between interfacial characteristics and the performance of devices.</p> <p>Therefore, the main theme of this thesis is to investigate the interfacial contacts of nanostructured solid-liquid interfaces by direct observation, and to develop a stable nanocomposite based on which the direct observation of the interfacial contact can be better conducted, and to eventually investigate the effect of interfacial contacts on the performance of organic solar cells.</p> <p>As the previous identification of the solid-liquid interface is limited to a microscale range, a direct method of tracing the different wetting states of water was developed, on nanostructured surfaces. This method provided an answer to a long standing question of, whether there is a transition from Wenzel to Cassie states in the sliding angle drop on nanocomposite thin films. In order to complete the observation of the wetting states of water, a stable superhydrophobic nanocomposite thin film with hierarchical structure was developed.</p> <p>Furthermore, with the knowledge of identifying the wetting states and the preparing procedures of the nanocomposites, a surfactant-free small-molecule nanoparticle organic solar cell with a much improved fill factor was developed by spin coating. The inverse correlation of series resistance and parallel resistance was discovered, due to the morphology change and the variation of the charge carrier concentration near the donor-acceptor interface in small-molecule organic solar cells.</p> / Doctor of Philosophy (PhD)

<p>Electrochemical supercapacitors (ES) have become an attractive research interest in advanced power systems and found many applications as an energy storage device in number of areas. The fabrication of advanced electrodes with novel materials and new techniques plays a key part in determining the properties of ES. Conducting polymer polypyrrole (PPY) has been found to be a promising electrode material for ES due to its high pseudo-capacitance and good electrical conductivity.</p> <p>Polypyrrole (PPY) films were successfully obtained on stainless steel substrates by anodic electropolymerization. Anionic dopants such as 2,6-naphthalenedisulfonic acid disodium salt (NSA), chromotropic acid disodium salt (CHR) and gallic acid were used for the synthesis of PPY. The roles of additives in the electrodeposition process have been discussed. The deposition was performed galvanostatically or potentiodynamically and the electrochemical properties of PPY have been investigated and compared by using different characterization techniques.</p> <p>The comparison of the experimental data for NSA, CHR and gallic acid showed the influence of aromatic ring and OH groups on the capacitive behaviour of PPY films. Adherent PPY films were obtained from pyrrole solutions containing CHR as dopant. The specific capacitance (SC) increased with increasing pyrrole and dopant concentration in the solutions used for deposition. The PPY films prepared on stainless steel substrates by electropolymerization are promising electrode materials for ES.</p> / Master of Applied Science (MASc)

<p>Dye-sensitized Solar Cells (DSSCs) with liquid electrolyte lack long term stability because of volatility of the electrolyte and assembly problems. Replacement of the volatile liquid-state electrolyte with solid-state hole conductor thus becomes necessary. A small molecule based hole conductor, Copper Phthalocyanine (CuPc), is proposed here to replace the liquid electrolyte, for its intrinsic thermal and chemical stabilities. However, a lower short circuit current was found in the CuPc solid state device from I-V curve, which is closely related to the inefficient hole transport in the CuPc thin film. Therefore, Two-Dimensional Grazing Incidence X-ray Diffraction (2D GIXRD) is utilized to study the phase and texture of CuPc thin film. It is found that the CuPc thin film has a cystallinity of greater than 80%, which is good for hole conducting. However, the <em>β</em>-phase formation lowers the overall hole conductivity. The hole conductivity of <em>β</em>-phase CuPc is two orders of magnitude smaller than that of <em>α</em>-phase CuPc, due to a less overlap in the <em>π-π</em> stacking. As a result, the low hole conductivity of <em>β</em>-phase CuPc is the reason that leads to an inefficient hole transport and reduces the short-circuit current of the solid-state DSSC. Therefore, future work will be necessary to isolate <em>α</em>-phase CuPc, in order to be successfully applied into the solid-state DSSCs.</p> / Master of Science (MSc)

<p>Effects of a nanometer-size, reactive polyhedral oligomeric silsesquioxane (POSS) on a thermoset’s polymerization kinetics and dielectric relaxation have been investigated by using differential scanning calorimetry (DSC) and dielectric spectroscopy. Four amines, hexylamine (HA), ethylene diamine (EDA), isophorone diamine (IPDA), and diethylene triamine (DETA) were used to crosslink epoxy resin DGEBA and a multi functionalized -glycidyl POSS. The polymers formed ranged from POSS-free to POSS-only network structure, while maintaining an equal ratio of reactive groups.</p> <p>Calorimetric studies of stoichiometric DETA and IPDA samples performed by ramp-heating showed that the polymerization kinetics increased with low POSS content, but progressively decreased upon further addition, and the POSS-only mixtures reacted the slowest. The same pattern of changes in the rate of polymerization was observed by isothermal polymerization of the DETA mixtures. The results have been interpreted based on changes in viscosity and diffusion coefficients according to the Stokes-Einstein and Smoluchowski equations. Furthermore, isothermal polymerization of stoichiometric DETA and EDA samples showed that the extent of reaction increased with POSS, indicating that it might be easier to form a higher crosslinked thermoset with higher amounts of POSS.</p> <p>Non-isothermal polymerization of POSS-IPDA mixtures was also investigated under off-stoichiometric conditions. Unlike the reaction mechanisms of non-stoichiometric DGEBA-IPDA mixtures, a significant difference in reactivity of primary and secondary amines in the POSS-IPDA reaction was not observed.</p> <p>Dielectric relaxation studies were performed in real time during polymerization. The distribution of relaxation rates increased with an increase in POSS, and the duration of polymerization required to reach a specific relaxation time increased. Furthermore, the time at which the dielectric loss minimum and peak occurred increased with POSS, however, when only POSS was reacted with the amine, an <em>a</em>-relaxation peak was not observed. A frequency-dependent increase in permittivity during polymerization was observed with the POSS-only EDA, DETA, and HA samples, and a corresponding change in the loss was not detected. It was attributed to a structure-dependent increase in interfacial polarization.</p> <p>Although not related to the polymerization study, work done on the residual entropy of glasses is included here. To help resolve the controversy of the residual entropy of glassy materials, specific heat data taken from the literature were analyzed. The changes in entropy of a glass on cooling and heating paths were determined, and it was found that the upper and lower limits of entropy differed by no more than 2 %. This showed that although the thermodynamic path through the glass transition is irreversible, this irreversibility has a negligibly small effect on determining the entropy.</p> / Master of Applied Science (MASc)

<p>The development of all-electric or plug-in hybrid vehicles requires the use of advanced energy storage devices with high power. Dedicated for energy storage, electrochemical supercapacitors (ES) offer the advantage of high power density. High power ES can provide load-leveling for batteries and fuel cells during starting, acceleration, hill climbing and braking. ES are important for reducing cycling of batteries, thus extending their lifetime by energy storage and delivery during fast transient operations such as in braking (storage) or start up and acceleration (supply).</p> <p>The interest in polypyrrole (PPY) for the application in ES is attributed to the high specific capacitance (SC) of this material. The possibility of PPY deposition on stainless steel substrates is important for the practical applications of PPY films in ES, using low cost stainless steel current collectors. The important task is to avoid anodic dissolution of the substrates during PPY electropolymerization. Polypyrrole (PPY) films were electrochemically deposited on stainless steel substrates or Ni plaque from aqueous pyrrole solutions containing anionic additives. The method resulted in the formation of adherent and uniform films. The deposition yield was investigated at galvanostatic conditions. It was found that anionic additives can be used for the dispersion of multiwall carbon nanotubes (MWCNTs) and fabrication of composite PPY–MWCNT films. The deposition yield was studied under galvanostatic conditions. The mechanism of PPY–MWCNTs deposition was discussed. The incorporation of MWCNTs into the PPY during electropolymerization resulted in the formation of porous films. The films were investigated for the application in electrodes of electrochemical supercapacitors. Electrochemical testing in the 0.5M Na₂SO₄ electrolyte solutions showed a capacitive behaviour in a voltage window of -0.5 to +0.4 V versus a saturated calomel electrode. The results indicated that the PPY–MWCNT films deposited on the stainless steel and nickel plaque substrates are promising electrode materials for ES.</p> / Master of Applied Science (MASc)

<p>Electrochemical methods show great promise in the deposition of biocompatible coatings for biomedical applications with advanced functionality. Consequently, methods of creating coatings of bioactive materials, such as halloysite nanotubes (HNT), hydroxyapatite (HA), chitosan, hyaluronic acid (HYH), poly-L-ornithine (PLO) and poly-L-lysine (PLL) and polyacrylic acid (PAA) have been developed through the use of electrophoretic deposition (EPD). The co-deposition of these materials are achieved at voltages ranging from 5 to 20 V on a 304 stainless steel substrate using suspensions of 0.5 and 1.0 gL^-1 biopolymer (chitosan, PAA, PLO, PLL) containing 0.3, 0.5 0.6, 1.0 and 2.0 gL^-1 bioceramic (HNT, HA). The resulting films were then investigated to further understand the kinetics and mechanics of deposition, determine their properties, and evaluate their suitability for physiological applications. The films were studied using X-Ray Diffraction (XRD), Differential Thermal Analysis and Thermogravimetric Analysis (DTA/TGA), Scanning Electron Microscopy (SEM), Quartz Crystal Microbalance (QCM) and Linear Polarisation. The results indicate that film thickness, composition and morphology can be controlled and modified at will, and that the deposition of composite films, multilayer laminates and functionally graded films are possible.</p> / Master of Applied Science (MASc)