Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 133-137). Also available on the World Wide Web.

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A capsule-based self-healing cementitious material, capable of autonomically repairing its own cracks, can extend the service life of concrete structures and decrease the costs associate with repair and maintenance actions. However, the size, shell thickness, shell material and mechanical properties of the capsules still need to be optimised to ensure self-healing performance. Thus, the objective of this research was to explore the controlled microfluidic encapsulation to investigate the production of microcapsules for physically triggered self-healing in cementitious materials. A flow-focusing microfluidic device was used to produce double emulsions to be selectively photopolymerised to generate a core-shell structure. Subsequently, the physical triggering was assessed by embedding the produced microcapsules in cement paste, fracturing it and observing the cracked surface in the SEM. The results showed the production of microcapsules with 80-140 μm of diameter with excellent control over size and shell thickness. Using water-in-oil-in-water (w/o/w) double emulsion, microcapsules were synthesised containing water, colloidal silica solution and sodium silicate solution as core material. In addition, an oil-in-oil-in-water (o/o/w) double emulsion was used to encapsulate mineral oil and emulsified healing agents. The formation of the core-shell structure with aqueous and organic cores was characterised using optical microscopy and SEM. It was demonstrated that the water is not retained inside of the capsule, resulting in the formation of dimples and buckled capsules, particularly for shells thickness ~7 μm. On the other hand, TGA confirmed the retention of mineral oil for shells thickness of ~2 μm and the encapsulation efficiency was demonstrated to be 66%. When the capsules were added to the cement paste, four key factors were observed to prevent physical triggering: (i) thick shells, (ii) buckling of thinner shells due to the loss of water core, (iii) mechanical properties and (iv) poor interfacial bonding. As a result, a mechanical characterisation of the shell material was performed, indicating brittle fracture at room temperature, reduced Young’s modulus when compared with cementitious matrix and stress at rupture of 15-36 MPa. In addition, an innovative methodology was proposed to functionalise the surface of the microcapsules with hydrophilic groups in order to increase the interfacial bonding between the cement paste and the microcapsules. Thus, microcapsules with low tensile strength, low shell thickness, organic core and good interfacial bonding were successfully synthesised and demonstrated to rupture upon crack formation. These results experimentally demonstrate the importance of reduced shell thickness, core retention and interfacial bonding as valuable guides during the design of microcapsules for physically triggered self-healing in cementitious materials.

The integration of droplet microfluidics devices with nanopore sensors offers a powerful and miniaturized sensing platform. Such devices can utilize the pre-processing capabilities of microfluidics in conjunction with single molecule sensing offered by nanopores. Microfluidics devices utilizing segmented flow (droplets) allow the compartmentalization of chemical and biological reagents in droplets reducing the processing time and associated cost, which is advantageous to biomolecular applications. Droplet microfluidics have been used in diagnostics and therapeutic applications such as cell and biomarker detection, gene amplification, and drug delivery. Nanopore sensors are currently used in investigating DNA and gene detection, protein-protein interactions, protein folding, and enzymatic kinetic reactions. This thesis proposes a design and outlines a methodology to integrate nanopore sensors within a droplet microfluidic device. The chapters are organized in highlighting three main objectives. The first objective is creating the segmented flow of oil-KCl droplets using a T-junction microfluidic design. The second objective is measuring the conductance of the segmented flow prior to the nanopore integration by using two side channel-AgCl electrodes. Subsequently, the third objective is integrating the droplet microfluidic device with a silicon nitride chip for nanopore fabrication. The nanopore is then created using controlled dielectric breakdown (CBD) method for DNA detection within droplets. The results show the feasibility of sensing individual DNA molecules within droplets using a nanopore sensor. The implemented approach expands upon nanopore applications to detect different samples simultaneously, fast food-borne pathogens and tumor discrimination in cancer biology. We anticipate that this integration is the future of nanopore sensors.

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

Diagnostic biosensors are on the rise in the global market due to the increasing prevalence of diseases. Specifically, the point-of-care segment has made great strides due to the improvement of biosensors' user-friendliness, simplicity, and clinical capabilities in the comfort of one's home. Although there are conventional diagnostic techniques, they are mutually time-consuming, costly, and labor-intensive. Not to mention, they are primarily dependent on bench-top or large immovable equipment. The widespread availability of smartphones has potentiated optical biosensors towards delivery of rapid and point-of-care diagnostic biosensors. Due to the affordability and user-friendliness of smartphones, smartphone-based biosensors may become ubiquitously available. Additionally, microfluidic platforms possess small footprints and portability towards development of true point-of-care and real-time diagnostic biosensors. In this dissertation, development of multiple diagnostic biosensors on microfluidic platforms is discussed. Diagnostic biosensors equipped with a smartphone-based optical detection show great promise of bringing clinical and bench-top laboratory capabilities for the convenience of the user, with reduced time, costs, and labor requirements. The widespread availability of point-of-care and real-time diagnostic biosensors may show promise in securing global health.

In the present study methods which can be integrated into a complete lab on a chip system for the detection and characterisation of Giardia duodenalis cysts and Cryptosporidium spp. oocysts from foods were developed and tested. Microfluidic chips, which make use of inertial separation, were designed and fabricated for the concentration and separation of either cysts or oocysts from food particles. These chips were highly specific for their intended target and were shown to be effective when used for artificially contaminated lettuce samples. The quantification by real-time PCR of Cryptosporidium spp. hsp70 mRNA, expressed in response to a heat stress, was assessed as a potential lab on a chip method for the detection of viable oocysts from foods. This method proved to be effective in determining the viability of oocysts in apple cider and the effects of high hydrostatic pressures on the viability of oocysts.

No description available.

Immunotherapy is becoming recognized as a superior treatment for cancer. In recent years, chimeric antigen receptor (CAR) therapy is among the immunotherapies that has had growing success rates. CAR T-cell therapy takes patient’s T-cells and encodes them with a CAR expressing gene, which can then target their cancer cells. However, there are some dangers associated with this therapy. If a cancer cell is mistakenly transfected with the CAR molecule, it can become resistant to the therapy. Using the electric properties of the cells, we have created a technique that can purify the T-cells from the remaining cancer cells using microfluidics and dielectrophoresis (DEP). Then, to further improve the therapy, the sample is electroporated following being patterned using DEP forces, which transfects the cells without using viral vectors and provides longer CD19 expression.

archives@tulane.edu / Structural changes in the cytoskeleton during metastatic transformation make cancer cells more deformable, and recent experimental studies confirm a direct correlation between cell invasiveness and cell deformability. Several microfluidic approaches have recently developed to exploit this cellular property for high-throughput assessment of metastatic risk from small samples of patient’s blood. While demonstrating feasibility in the lab, these technologies often lack a solid theoretical foundation or do not show adequate sensitivity to cellular mechanical properties (“mechanotype”). The long-term goal of this project is to optimize microfluidic tests for metastatic risk assessment, including circulating tumor cell (CTC) isolation and mechanotype analysis, through predictive computational modeling. Specific aims of the presented study are 1) to expand the capability of our custom computational algorithm for viscoelastic cell deformation and migration to simulate cell sorting and CTC isolation in channels with complex geometry, including channels with pillars and bifurcations, and 2) to demonstrate the capability of our algorithm to optimize microfluidic methods for cancer cell mechanotype measurement. / 1 / Scott J. Hymel