Mechanical Engineering
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Item Open Access Long-Wavelength Infrared Thermophotonic Imaging of Demineralization in Dental Hard Tissue(2016-11-25) Ojaghi, Ashkan; Tabatabaei, NinaEarly detection of the most prevalent oral disease worldwide, i.e., dental caries, still remains as one of the major challenges in Dentistry. Current dental standard of care relies on caries detection methods which lack the sufficient specificity and sensitivity to detect caries at early stages of formation when they can be healed. In this thesis, a clinically and commercially viable thermophotonic imaging (TPI) technology capable of detecting early enamel caries using an inexpensive long-wavelength infrared (LWIR, 8-14m) camera is presented. Through theoretical modelling and experiments on standard samples, the enhanced diagnostic contrast in LWIR detection compared to existing MWIR detection technologies is verified. Diagnostic performance of the system and its detection threshold are experimentally evaluated by monitoring the inception and progression of artificially-induced occlusal and proximal caries as well as natural early caries. The results are suggestive of the suitability of the developed LWIR system for detecting early dental caries.Item Open Access Novel Techniques for Water Treatment(2017-07-26) Dasgupta, Saumyadeb; Mitra, SushantaA rapid decline in the quality of drinking water sources across the world has emerged as a considerable threat to human life. Maintaining a continuous supply of clean drinking water is a challenging task in rural and marginalized communities, where conventional methods of monitoring and treatment cannot be implemented due to a lack of appropriate infrastructure and skilled personnel. Hence, the main focus of the present thesis is to develop better water quality monitoring and purification techniques targeted towards portable point-of-use systems. The approach towards better water quality monitoring involves the development of a rapid and portable concentrating device which can be used in conjunction with microfluidics based biosensor platforms to detect pathogens in contaminated water. The solution to the problem of water treatment involves the assessment of a naturally available antimicrobial agent, the Moringa oleifera seed extract, followed by its integration into a novel and truly sustainable device capable of removing bacterial loads from contaminated water.Item Open Access Hybrid Microfluidic Devices For On-Demand Manipulation and Screening of Neurons and Organs of Small Model Organisms(2017-07-26) Ardeshiri, Ramtin; Rezai, PouyaCaenorhabditis elegans and Drosophila melanogaster are widely used model organisms for neurological and cardiac studies due to their simple neuronal and cardiac systems, genome similarity to humans, and ease of maintenance in laboratories. However, their 50m-1mm sizes and continuous mobility impede their precise spatiotemporal manipulation, thereby, reducing the throughput of biological assays. By integrating glass capillaries into microfluidic devices and using 3D-printed fixtures for precise control, we have developed hybrid lab-on-a-chip devices to facilitate the processes of animal manipulation and stimuli control, using modules for single-organism selection, orientation, imaging and chemical stimulation. These microdevices enabled us to manipulate organisms individually and to orient them at any desired direction for imaging purposes. The applications of these hybrid microdevices were demonstrated in the optical and fluorescent imaging of C. elegans cells as well as cardiac screening of Drosophila larvae. This technique can be applied in fundamental biology, toxicology, and drug discovery.Item Open Access Inertio- and Elasto-Magnetic Fractionation of Multiple Microparticles in Newtonian and Non-Newtonian Fluid(2017-07-27) Kumar, Vikash; Rezai, PouyaSorting of microparticles and cells using microfluidic platforms has several applications in diagnosis, biotechnology, and medicine. However, the currently available microfluidic sorting techniques have one or more of the following drawbacks such as low throughput, need for diluting sheath flows for operating devices, inability to sort multiple particles simultaneously, low purity and requirement of complicated fabrication methods. In this thesis, a hybrid scheme for sheath-less fractionation of microparticles has been devised by integrating magnetophoresis, inertial focusing and elastic focusing approaches with the concept of pinched flow fractionation. We have taken advantage of inertia, magnetic, drag, and elastic forces to achieve high throughput multiplexed microparticle fractionation. The technique has been tested with respect to parameters such as size of particles, flow rate, device geometry and fluid viscosity (Newtonian vs. non-Newtonian). This sorting method offers a tool to handle heterogeneous samples and can be used for affinity-based immune-magnetic separation of biological substances.Item Open Access Asymmetric Behavior of a Drop Upon Impact onto a Surface(2017-07-27) Almohammadi, Hamed; Amirfazli, AlidadIn this thesis, a systematic study was performed to understand drop impact onto hydrophilic and hydrophobic moving surfaces. Different systems (combination of liquids, surfaces, and drop impact conditions) were examined. Wide range of normal drop and surface velocities were studied; such normal and tangential velocity ranges are not available in systems where a drop impacts at an angle relative to a surface. The asymmetric nature of drop spreading on moving surfaces was elucidated. A model that for the first time is able to mathematically predict the time evolution of such asymmetric spreading was provided. Furthermore, a new model was developed to determine the splashing threshold of the drop impact onto a moving surface. The model is capable of describing the azimuthally different behavior of splashing. The effect of liquid viscosity on drop splashing was clarified. A comprehensive regime maps of drop impact outcome on a moving surface was provided.Item Open Access Behavior of Liquid Bridges between Nonparallel Surfaces(2017-07-27) Ataei, Mohammadmehdi; Amirfazli, AlidadFormation of liquid bridges between two solid surfaces is frequently observed in industry and nature, e.g. printing. When the two solid surfaces are not parallel (with dihedral angle between them), two significant phenomena emerge in the bridge behavior: First, if exceed a critical angle (_c), the bridge is no longer stable and propel itself horizontally towards the cusp of the surfaces. Second, if a stable bridge is squeezed and stretched, a horizontal bulk motion of the bridge along the surfaces can be observed. Through both experimental and numerical studies, we demonstrated that _c can be increased by increasing advancing contact angle (_a), and Contact Angle Hysteresis (CAH) of the surfaces. We also demonstrated that the magnitude of the bulk motion can be increased by increasing , the amount of compressing and stretching, and/or by decreasing _a and CAH of the surfaces.Item Open Access Under Liquid Wetting Dynamics(2017-07-28) Mitra, Surjyasish; Mitra, SushantaLiquid drops wetting a surface kept in ambient air has been widely studied over the last few decades due to its manifold applications in technology and industry. However, for a surface kept submerged under-liquid, such wetting processes have been studied to a lesser extent. Understanding how a liquid drop interacts with a surface in the presence of another liquid medium is pivotal towards growing applications in marine ecosystem, environmental effects of oil-spills, advanced manufacturing techniques like immersion lithography, etc. It also poses the challenging issues of liquid-liquid displacement and contact line dynamics. The present study delineated some fundamentals of under-liquid wettability like coalescence of two sessile drops on an under-liquid substrate, spreading of liquid drops on an underliquid substrate and drop interaction with submerged micro-patterned substrates.Through relevant theoretical analysis as well as experimentation, it was found that the existing theories of drop interaction with a surface in air are inadequate when a surrounding liquid medium is considered, and needs to be modified bringing into effect key parameters of the surrounding medium, such as its density and viscosity. Consideration of a surrounding liquid medium also allows to provide a unifying framework to study such wetting processes. For coalescence and spreading, a universal behavior was observed in terms of the initial fast wetting regime inherent to such processes, and the notion of coalescence-spreading analogy was found acceptable to describe such phenomenon. However, for under-liquid wetting signature of micro-patterned substrates, a non-universal behavior was observed which indicates the need of newer theoretical approach to better understand wetting phenomenon on such under-liquid surfaces.Item Open Access Investigation of Secondary (Dean) Flows in Curved Microchannels and Application to Microparticle Sample Preparation(2018-03-01) Bayat, Pouriya; Rezai, PouyaExchanging the solution of microparticles from a complex source fluid to a target clean buffer is important for sample preparation in portable microfluidic and point-of-care diagnostic devices. Current portable solution exchange methods are often limited in throughput or have low efficiencies. In this thesis, a novel method involving inertial focusing of microparticles at the inner wall of a curved channel and secondary Dean flow-based exchange of their fluid is investigated. The fluid behavior in curved microchannels is thoroughly studied and the effects of radius of curvature, hydraulic diameter, width and height of the channel and viscosity of the fluid on the development of Dean vortices are investigated experimentally and numerically. A comprehensive correlation for estimating the average lateral Dean velocity of the fluid is also proposed. The outcomes of the fluidic study is then combined with inertial particle focusing to devise a microfluidic platform for exchanging the solution of 11 m and 19 m microparticles. This was achieved with an unprecedented flow rate of 1 mL/min and throughput of 10000 particle/s at high efficiencies. Additionally, the application of the device for isolation of cell surrogates from a bacterial solution is shown. This technology can be used as a portable micro-centrifuge for sample preparation in point-of-care devices.Item Open Access Effective Mechanical Properties of 3D Structural Metamaterials(2018-03-01) Abdelhamid, Mohamed Abdelaziz Abdelrahma; Czekanski, AlexRecent advances in fabrication techniques have enabled the creation of novel materials with enhanced mechanical properties commonly known as metamaterials. They refer to materials consisting of a unit cell tessellated in three orthogonal directions with dimensions scaling down to the nanoscale. The objective of this research was to describe the effective properties of the octet-truss unit cell at different lattice angles and loading directions. The research is composed of three consecutive parts. The first part addressed the analytical derivation of the continuum-based model while including the lattice angle. The second part demonstrated the impact of the lattice angle on its effective properties, namely relative density, effective stiffness, and effective strength. Finally, potential in lattice structure optimization is demonstrated through an experimental study. This work addressed optimizing the structural configuration of the octet-truss, which when combined with favorable size effects, would unlock the full potential of mechanical metamaterials as load-bearing structures.Item Open Access Shedding of Multiple Sessile Droplets(2018-05-28) Razzaghi, Aysan; Amirfazli, AlidadA droplet which is placed on a surface and is exposed to an airflow, can be shed, if the drag force overcomes the droplets adhesion force. Presence of other sessile droplets, in proximity, changes the drag force, so the minimum airflow velocity required to shed the droplets (Ucr) can vary. In this thesis, an experimental study on shedding of the multiple sessile droplets was performed on both hydrophilic and hydrophobic surfaces. The effects of the droplets arrangement type, and the spacing on Ucr were elucidate. For a pair of sessile droplets, a model was proposed to predict the Ucr based on droplets size, spacing, arrangement, and surface wettability. For three, or four sessile droplets arranged in triangle, square, reversed triangle, and diamond configurations, the effects of the droplets interaction on variation of the Ucr, was clarified. A critical value for spacing was determined beyond which multiple sessile droplets shed independently.Item Open Access Development of Thermoplastic Polyurethane-Hexagonal Boron Nitride Composite Foams with Enhanced Effective Thermal Conductivity(2018-05-28) Ghariniyat, Parisa; Leung, Siu-NingThermoplastic polyurethane (TPU)-hexagonal boron nitride (hBN) composites fabricated by batch foaming were studied in this study. The results of this research demonstrated that by CO2 foaming it was possible to produce TPU foams at relatively low temperatures (60C). The results indicated that the cell size and cell density range are significantly wider at lower saturation pressures to varying foaming temperatures. While TPU foams usually yield extremely high cell population density and small cell size, by applying the appropriate foaming conditions, we prepared foams with a wide range of cell sizes, from 21 to 170 m, and cell population density from 105 to 108 pore/cm3. These conditions have been used to investigate the foaming-assisted filler alignment in TPU composite and nanocomposite foams for tailoring the thermal conductivity. Foamed samples at lower saturation temperatures (i.e. 20 and 40C) yielded higher thermal conductivity than solid counterparts.Item Open Access Thermal Fe Analysis of Powder Bed Fusion Process: Power Input Evaluation and Parameter Sensitivity(2018-11-21) Moraes, Diego Augusto De; Czekanski, AlexWe investigated the thermal behavior of the powder bed fusion (PBF) manufacturing process. Specifically, a finite element thermal analysis procedure was developed to simulate selective laser melting, one of several PBF processes available on the market. The primary objective was to study how selected parameters of the PBF process affect temperature distributions, since a high temperature gradient and cooling rate are associated with residual stress and deformation in the built part. Since it was difficult to devise an analytical solution for this transient thermal problem, commercially available finite element analysis software, Abaqus, was employed. Sensitivity analysis was undertaken to analyze the impact of powder diameter, packing density, and substrate temperature on the overall temperature distributions. Finally, verification and validation were performed via experimental setup and data from the literature. The samples built were characterized by residual stress measurements, porosity, and relative density to further validate the model.Item Open Access Micro-and-Nanostructuring of Polyvinylidene Fluoride with Tailored Crystal Polymorphs and Enhanced Piezoelectric Property(2018-11-21) Lee, Ji Eun; Leung, Siu-NingPolyvinylidene fluoride (PVDF) has garnered interest due to its piezoelectric property and as a non-toxic, conformable, and low-cost alternative to the popular piezoelectric ceramic. A novel processing method through the combination of thermal and supercritical carbon dioxide (ScCO2) has been used to successfully promote the formation of electroactive phases (i.e., beta and gamma phases), as well as its piezoelectric property. In this report, the processing-to-structure properties and mechanisms that affect crystallization behaviors of electroactive phases were elucidated. It was revealed that gamma crystal formation was through thermal processing while beta phase was nucleated through fast cooling and physical foaming of CO2 bubbles. The results were comparable to common processing method and literature, with a maximum electroactive crystal phase of 72.2% and a corresponding piezoelectric coefficient of 7.7 pC/N. The findings in this study could provide insight to future research work on PVDF, advancing its development in piezoelectric applications.Item Open Access Preparation and Characterization of Bio-based PCM Microcapsules for Thermal Energy Storage(2018-11-21) Fashandi, Maryam; Leung, Siu-NingPhase change materials (PCM) have gained extensive attention in thermal energy storage applications. During their phase transition, the energy can be stored in or released from PCM. While changing from solid state to liquid state, PCM start to flow. Encapsulation is a widely-used technique to prevent PCM from migrating and reacting with their environment. In the first phase of the thesis, microencapsulation of 100% bio-based (organic) PCM microcapsules by solvent evaporation and oil-in-water emulsification was investigated under different conditions, resulting in optimal properties. For the second phase, the focus was on the studies of inorganic PCM, which have higher latent heat of melting, higher thermal conductivity and lower price than the organic PCM. However, their supercooling, phase segregation, and hydrophilic nature have caused major challenges to their applications. Tuning the thermal properties, including crystallization temperature and phase segregation of inorganic PCM by using bio-based nanoparticles and other additives was investigated in the second part of the research. Due to the hydrophilic nature of the inorganic PCM, a double emulsion (water in oil in water) solvent evaporation technique was explored for encapsulation with a polymeric shell. The challenges and strategies for supercooling prevention and encapsulating the hydrophilic PCM were investigated.Item Open Access Drop Impact on an Inclined and a Moving Surface(2018-11-21) Sookran, Salman Buksh; Amirfazli, AlidadThis thesis has made progress in two different areas related to drop impact onto a surface. Firstly, a systematic experimental study has been performed to understand asymmetric spreading of low and high surface tension liquids on a moving surface. A new time evolution model for droplet spreading on a moving surface was developed. This model regardless the value of surface tension of the liquid can predict the spreading of low viscous (1-4cSt) liquids on a moving surface. Secondly, liquids with viscosity (1-5cSt) and surface tension (17.4-72.8mNm) were used to study the drop impact on moving and inclined surface. Experiments performed with similar normal (0.9-2.9m/s) and tangential (0.8-2.9m/s) velocities on both surfaces to test our hypothesis that spreading/splashing for these two surface conditions should be same. Results indicates that our hypothesis is true, except for some special conditions when, normal and tangential velocities are greater than the range of our analysis.Item Open Access Oscillating Dispersed-Phase Co-Flow Microfluidic Droplet Generation: Effects on Jet Length and Droplet Size(2019-03-05) Shams Khorrami, Amin; Rezai, PouyaDroplet-based microfluidics have emerged as versatile platforms offering unique advantages in biology and chemistry. Although there is adequate control on size and monodispersity, most conventional microfluidic techniques cannot generate more than one droplet size at a time in a continuous and high-throughput manner. Moreover, the widely used co-flow microfluidic droplet generation technique is bottlenecked with droplet polydispersity at high throughputs due to the transition from a more-stable dripping regime to an instable jetting regime at high d-phase flow rates. We applied nozzle oscillatory motion to generate an axial shear gradient as well as inducing an additional transverse drag force. We hypothesized that the combined effects of axial and transverse drags can be used for overcoming the aforementioned limitations of co-flow systems. Nozzle oscillation effect was studied in both dripping and jetting regimes to generate repeatable patterns of multi-size monodisperse droplets and jet length reduction in different biphasic systems, respectively.Item Open Access Fabrication and Characterization of Self-Sensing Nanocomposite - "Smart Skin"(2019-03-05) Sidhu, Gurtej Singh; Zhu, GeorgeThis study characterizes the behaviour and properties of self-sensing polymer nanocomposite. Specifically, we studied the Electrical, Mechanical and Piezoresistive properties. Electrically the material is conductive with a linear response to change in applied strain. Mechanically the material behaves like a polymer, whose Youngs Modulus increases with added MWCNT. From a piezoelectricalperspective this material is stable and can maintain its electrical and mechanical behaviour for 50 cycles of repeated loading at 2mm/min. When producing thin sheets of nanocomposite, the effects of material thickness on piezoresistivity are negligible. The nanocomposite is fabricated by mechanically mixing multiwalled carbon nanotubes (MWCNT) with 2-part polydimethylsiloxane (PDMS). The randomly aligned MWCNT-PDMS is fabricated for two configurations, Type I and Type II. In these configurations, Type I is read longitudinal to force using 4-Probe method and Type II is read perpendicularly with 2-Probe method. The strain is applied to Type I in tension and Type II in compression. The Type I characterizes the bulk conductivity for varying wt% of MWCNT. The Type II looks at the sheet conductivity for varying thickness.Item Open Access Microfluidic Devices for Investigation of Zebrafish Larvaes Electrotaxis and their Applications to Dopamine System Studies(2019-03-05) Peimani Foroushani, Amir Reza; Rezai, PouyaZebrafish (Danio rerio) have been used as a model organism for behavioral screening assays due to their high genetic homology with humans. However, research on zebrafish sensory-motor responses to electrical stimuli, called electrotaxis, has been overlooked. We demonstrated the larvae could orient and swim towards the anode and increasing the electrical strength resulted in a stronger electrotaxis. Also, the zebrafish tended to exhibit a lower electrotaxis during the night than the daytime. We showed that electrotaxis is modulated by their D2-like dopamine receptors. Moreover, we examined the tail-beat frequency (TBF) and response duration of zebrafish electrotaxis. We observed that the highest TBF occurs at the lowest current while the response duration was longest at the intermediate currents. We also explored the role of Pannexin1 protein membrane (Panx1) in the zebrafish. It was shown that Panx1 might play an effective role in modulating electrotaxis at lower currents.Item Open Access In Pursuit of an Optimum Optical Imaging Technology for Early Detection of Dental Caries(2019-03-05) Baradaran Shokouhi, Elnaz; Tabatabaei, Nima NimaClinical caries detection techniques, such as radiographs, are not sensitive to detect and monitor the progression of caries at early stages. In recent years, several optics-based imaging modalities have been proposed for early detection of caries. In this thesis, we report on a systemic comparative study on the performances of optical coherence tomography and thermophotonic lock-in imaging (TPLI) as early caries detection imaging modalities based on light scattering and absorption, respectively. Through controlled demineralization on extracted human teeth, our results suggest that TPLI provides better sensitivity and detection threshold in detecting early stages of caries. The outcome justifies the need for a light-absorption based imaging modality to produce depth-resolved images. Therefore, preliminary imaging studies on a 3-D imaging platform known as a Truncated-Correlation Photothermal Coherence Tomography (TC-PCT) system was conducted to achieve optimal diagnostic yield. The results demonstrate that TC-PCT can detect early caries with significant enhancement in depth-resolution.Item Open Access Novel Reconfigurable Delta Robot Dual-Functioning as Adaptive Landing Gear and Manipulator(2019-07-02) Arns, Moritz; Zhang, DanIn this work a novel dual-functioning rotorcraft undercarriage is developed. The design is a reconfigurable delta robot which allows for transformation between Adaptive Landing Gear for vertical take-off and landing and 3DOF Aerial Manipulation mode. To reconfigure between operation modes without reaching singularities, a guideline to find a singularity-free geometry is presented. An adaptive landing control was developed and validated on a test-stand. For the 3DOF manipulation of the delta-structure, a third-order smooth trajectory was presented and integrated. The prototype, also depicted in the accompanying video, is then presented in free flight experiments demonstrating the advantages of the dual-functioning system.