We present a platform that allows homogeneous and heterogeneous 3-D soft materials to be continuously defined in a single step. Biopolymer solutions are introduced to a microfluidic device and radially distributed to feed to a common outlet at the device center. This forms concentric sheaths of complex fluids and upon crosslinking, a hydrogel tube at the exit. This approach allows for the controlled and continuous extrusion of tubes with tailored diameters of 500 μm to 1500 μm, wall thicknesses of 20 μm to 120 μm, and compositions, as well as predictable mechanical and chemical properties. Using the same platform, single and multi-walled hydrogel tubes with defined heterogeneities and patterns of discrete spots of secondary biopolymer materials can be continuously extruded. A tube-hosting device is presented which can independently perfuse and superfuse isolated tube segments, allowing precise microenvironmental control without cannulation for up to an hour.

Recovery of the ability to maintain balance during standing is one of the primary and essential goals of rehabilitation programs for individuals with Spinal Cord Injury (SCI). Regaining functionality during standing by means of a neuroprosthesis would decrease secondary complications and increase independence, and would consequently improve the quality of life of these individuals. However, the development of a standing neuro- prosthesis requires techniques to generate reliable and predictable torque vectors in the lower limbs. We proposed and tested a method based on surface Functional Electrical Stimulation (FES) and the idea that three independent muscles can form a basis that would span the joint torque vector space. We tested the proposed stimulation technique on the quadriceps muscles that produce knee extension. The results of this study suggest that the quadriceps muscle basis vectors are insufficient to cover the knee joint vector space.

A methodology was developed to dissect diesel particulate filters to study the time effect of loading for two different fuels: ULSD and a biodiesel blend. Filters loaded with soot from a diesel engine for exposure times of 1, 2, 5 and 10 hours were fractured and samples of filter substrates were analyzed using Raman spectroscopy and scanning electron microscopy. Observations revealed the sharp rise in pressure drop to be attributable to the clogging of the pores in the channel wall, leading to the formation of a pore-bridge. Cross sectional imaging of wall sections revealed this pore-bridge to be shallow, with significant particulate depositions limited to the first quarter of the depth of the filter walls. Images revealed increasingly dense deposits and the formation of coarse particles and soot cakes. Raman spectroscopy revealed no significant graphitization of the soot cake. The dissection methodology exhibits significant potential for future studies on DPFs.

A methodology was developed to dissect diesel particulate filters to study the time effect of loading for two different fuels: ULSD and a biodiesel blend. Filters loaded with soot from a diesel engine for exposure times of 1, 2, 5 and 10 hours were fractured and samples of filter substrates were analyzed using Raman spectroscopy and scanning electron microscopy. Observations revealed the sharp rise in pressure drop to be attributable to the clogging of the pores in the channel wall, leading to the formation of a pore-bridge. Cross sectional imaging of wall sections revealed this pore-bridge to be shallow, with significant particulate depositions limited to the first quarter of the depth of the filter walls. Images revealed increasingly dense deposits and the formation of coarse particles and soot cakes. Raman spectroscopy revealed no significant graphitization of the soot cake. The dissection methodology exhibits significant potential for future studies on DPFs.

A half-zone experimental set-up was used to study the effects of various liquid bridge and helium flow parameters on the onset of thermocapillary convection in silicone oil liquid bridges. Experiments confirmed that helium flow has a stabilizing effect, with the effect increasing with helium velocity. Furthermore, helium flow in the same direction as surface flow due to Marangoni convection had a more stabilizing effect than countercurrent flow. It was established that increasing helium temperature has a mixed effect, producing a less stable bridge at low helium flow rates, but a more stable flow pattern at higher helium flow rates. Finally, it was confirmed that decreasing the cold disk temperature results in a decrease in critical temperature difference.

Research was performed on the development of metal-supported solid oxide fuel cell (SOFC) electrolytes by suspension and solution precursor plasma spraying (SPS and SPPS). Experiments were conducted to understand the effects of many plasma-, feedstock-, and substrate-related process parameters on the microstructure, permeability, and conductivity of the resulting coatings. Most work was performed with yttria-stabilized zirconia (YSZ), but samaria-doped ceria (SDC) was also considered. The plasma-to-substrate heat flux behaviour of the process is particularly relevant for producing dense electrolytes with low segmentation cracking. Heat flux profiles for various processing conditions were experimentally determined and then used to model temperature distributions in the electrolyte and substrate during deposition. The results showed a strong correlation between segmentation crack severity and the peak temperature difference between the electrolyte surface and the metal support during deposition. Building on these findings, two strategies were developed for improving electrolyte performance. The first strategy is to use a bi-layer electrolyte structure, in which one layer is dense but has segmentation cracks and the other layer is more porous but contains relatively few segmentation cracks. A cell with a bi-layer electrolyte achieved a peak power density of 0.718 W cm-2 at 750 °C using hydrogen as fuel. The second strategy involves reducing the thickness and roughness of the electrode on which the electrolyte is deposited, which first required the development of improved metal supports. A thinner electrode reduces the thermal stresses that drive segmentation cracking and a smoother surface minimizes the formation of concentrated porosity. A cell with a 16 μm thick anode and a 21 μm thick electrolyte achieved an open circuit voltage (OCV) of 1.053 V, a series resistance of 0.284 Ω cm2, and a peak power density of 0.548 W cm-2 at 750 °C using hydrogen as fuel. A separate cell with a 28 μm thick electrolyte achieved an OCV of 1.068 V. At the end of the thesis, cell performance is compared to that of state-of-the-art cells produced in other facilities and using other production methods.

One of the applications where the use of robots can be beneficial is Wilderness Search and Rescue (WiSAR), which involves the search for a possibly mobile but non-trackable lost person (i.e., the target) in wilderness environments. A mobile target implies that the search area grows continuously and potentially without bound. This fact, combined with the presence of typically rugged, varying terrain and the possibility of inclement weather, poses a considerable challenge to human Search and Rescue (SAR) personnel with respect to the time and effort required to perform the search and the danger entailed to the searchers. Mobile robots can be advantageous in WiSAR due to their ability to provide consistent performance without getting tired and their lower susceptibility to harsh weather conditions compared to humans. Thus, a coordinated team of robots that can assist human SAR personnel by autonomously performing searches in WiSAR scenarios would be of great value. However, to date, a suitable multi-robot coordination methodology for autonomous search that can satisfactorily address the issues relevant to WiSAR is lacking. The objective of this Dissertation is, thus, to develop a methodology that can autonomously coordinate the search strategy of a multi-robot team in wilderness environments to locate a moving target that is neither continuously nor intermittently observed during the search process. Three issues in particular are addressed: (i) target-location prediction, (ii) robot deployment, and (iii) robot-path planning. The corresponding solution approaches devised to address these issues incorporate the influence of varying terrain that may contain a priori known and unknown obstacles, and deal with unique target physiology and psychology as well as found clues left behind by the target. The solution methods for these three tasks work seamlessly together resulting in a tractable MRC methodology for autonomous robotic WiSAR. Comprehensive simulations have been performed that validate the overall proposed methodology. Moreover, the tangible benefits provided by this methodology were further revealed through its comparison with an alternative search method.

While tissue-engineering approaches of heart valves have made great strides towards creating functional tissues in vitro, the instruments used, named bioreactors, cannot efficiently integrate multiple stimuli to accurately emulate the physiological microenvironment. To address this, we conceptually designed and built a bioreactor system that applied a range of mechanical tension conditions, modulated matrix stiffness, and introduced biochemical signals in a combinatorial and high-throughput manner. Proof-of-concept experiments on PAVIC-seeded hydrogels were performed to assess the independent and combined effects of tensile strain, matrix stiffness and TGF-β1 on myofibroblast differentiation by measuring α-SMA expression, a marker that indicates a disease-associated phenotype. We found that matrix stiffness and TGF-β1 significantly increased α-SMA levels (p < 0.001), while the effect of mechanical strain was only significant on soft gels (~12 kPa) without TGF-β1. This study therefore demonstrated independent and integrated effects of multiple stimuli in regulating key cellular events in the aortic valve.

The proposed tension measurement method focuses on measurement of tension in a single belt span of the multi-pulley Front End Accessory Drive (FEAD) system. The mean belt span tension is calculated from the measured belt span natural vibration frequency. The oscillation belt span tension is calculated from the measured belt span transverse displacement. The dynamic belt span tension is calculated using the mean and oscillation tensions, belt span support pulley rotations, and belt slip, where the slip equation is based on Euler's equation. The proposed tension measurement method is validated using an experimental testing FEAD system which consists of a five pulley system and an automatic tensioner arm. Non-contact sensors are used to prevent disruption of the typical system behaviour. Testing conditions simulate typical engine crankshaft rotation input. Results from experimental testing consistently produce results with percent error less than 10 % for mean and maximum belt span dynamic tension.

A half-zone experimental set-up was used to study the effects of various liquid bridge and helium flow parameters on the onset of thermocapillary convection in silicone oil liquid bridges. Experiments confirmed that helium flow has a stabilizing effect, with the effect increasing with helium velocity. Furthermore, helium flow in the same direction as surface flow due to Marangoni convection had a more stabilizing effect than countercurrent flow. It was established that increasing helium temperature has a mixed effect, producing a less stable bridge at low helium flow rates, but a more stable flow pattern at higher helium flow rates. Finally, it was confirmed that decreasing the cold disk temperature results in a decrease in critical temperature difference.