In the developing world, there are large populations suffering from infectious diseases, many of whom are located in remote regions. With the rapid growth in microfluidic systems in recent years, complex functions of conventional diagnostic equipment have been miniaturized and integrated into small devices at the size of a credit card (so-called portable Point-of-care (POC) devices). In this thesis a novel approach to overcoming the challenge of in-field biological sample processing and preparation to produce high quality fluids that can be readily used for downstream testings is described and proof of concept experiments presented. This approach uses hydrodynamic effects and combines nanoporous membrane with microfluidic systems and to filter the cellular component of blood. Experiments presented here demonstrate successful cells filtration from whole blood. Employing hydrodynamic effects is also shown to be an effective and potentially useful technique to isolate cells and plasma within appropriate micro-architectures.

Laser scanning cytometry (LSC) is a slide-based method that is used clinically for Quantitative Imaging Cytometry (QIC). A “Clatch” slide, named after the inventor, which is used in conjunction with the LSC for immunophenotyping patient cell samples, has several drawbacks. The slide requires time consuming and laborious pipette steps, making the slide prone to handling errors. The Clatch slide also uses a significant amount of cell sample, limiting the number of analyses for fine needle aspirate (FNA) samples. This thesis details an automated microfluidic system, composed of an embedded circuit, a plastic and polymer microfluidic device, and an aluminum frame, which can perform the same immunophenotyping procedures. This new system reduces the labor from 36 pipette steps to 8, it reduces the amount of cell sample from 180 μL to 56 μL, and it shortens the entire procedure from 75 minutes to 42 minutes.

In this work, a MFC fabrication procedure including two non-conventional techniques (partial baking and cap-sealing) were employed for the development of an up-scaled microfluidic fuel cell (MFC). Novel carbon-based electrode materials were employed, including carbon foam, fibre, and cloth, the results from which were compared with traditionally-employed carbon paper. The utilization of carbon cloth led to 15% of the maximum power that resulted from carbon paper; however, carbon fibre led to a 24.6% higher power density than carbon paper (normalized by electrode volume). When normalized by projected electrode area, the utilization of carbon foams resulted in power densities up to 42.5% higher than that from carbon paper. The impact of catalyst loading on MFC performance was also investigated, with an increase from 10.9 to 48.3 mgPt cm-2 resulting in a 195% increase in power density.

In the developing world, there are large populations suffering from infectious diseases, many of whom are located in remote regions. With the rapid growth in microfluidic systems in recent years, complex functions of conventional diagnostic equipment have been miniaturized and integrated into small devices at the size of a credit card (so-called portable Point-of-care (POC) devices). In this thesis a novel approach to overcoming the challenge of in-field biological sample processing and preparation to produce high quality fluids that can be readily used for downstream testings is described and proof of concept experiments presented. This approach uses hydrodynamic effects and combines nanoporous membrane with microfluidic systems and to filter the cellular component of blood. Experiments presented here demonstrate successful cells filtration from whole blood. Employing hydrodynamic effects is also shown to be an effective and potentially useful technique to isolate cells and plasma within appropriate micro-architectures.

Microfluidic technology is a useful tool to help answer unsolved problems in multidisciplinary fields, including molecular biology, clinical pathology and the pharmaceutical industry.Current microfluidic based devices with diverse structures have been constructed via extensively used soft lithography orphotolithography fabrication methods. A layer-by-layer stacking of 2D planar microchannel arrays can achieve limited degrees of three dimensionality. However, assembly of large-scale multi-tiered structures is tedious, and the inherently planar nature of the individual layers restricts the network’s topological complexity. In order to overcome the limitations of existing microfabrication methodswe demonstrate several novel methods that enable microvasculature networks: electrostatic discharge,global channel deformation and enzymatic sculpting to fabricate complex surface topologies. These methods enable construction of networks of branched microchannels arranged in a tree-like architecture with diameters ranging from approximately 10 μm to 1 mm. Interconnected networks with multiple fluidic access points can be straightforwardly constructed, and quantification of their branching characteristics reveals remarkable similarity to naturally occurring vasculature. In addition, by harnessing enzymatic micromachining we are able to construct nanochannels, microchannels containing embedded features templated by the substrate’s crystalline morphology, and an irregular cross section of microchannel capable of performing isolation and enrichment of cells from whole blood with throughput 1 – 2 orders of magnitude faster than currently possible. These techniques can play a key role in developing an organ-sized engineered tissue scaffolds and high-throughput continuous flow separations.

Continuous perfusion cell culture chips offer the biomedical researcher unprecedented control over the microenvironment surrounding the cell which is not feasible with conventional static cell culture procedures. Applying microfluidics technology to these devices provides several benefits including increased fluid and media control, reduced consumption of reagents, continuous monitoring of cells and the potential for massively parallel experiments. In this work a new continuous perfusion cell culture chip is studied that utilizes electroosmotic pumping to control fluid flow. Problems associated with EOF and cells are solved by incorporating electroosmotic pumps (EO pumps) which generate an induced pressure driven flow in regions with cells. Several advantages of EO pumps include pulse free flow, quick flow control and precise movement of minute volumes of fluid. However, the high salt concentration in cell culture medium creates significant problems for EO pumps such as decreased flow rate due to low zeta potential, increased electrolysis due to large current draw, significant joule heating, bubble formation and polarization. Attempts to solve these problems with the proposed microfluidic chip are discussed. The microfluidic chip is fabricated using soft lithography techniques developed as part of this work. The designs were modelled using a combination of numerical simulations with a commercial software program and compact circuit modelling. The pumps were integrated on-chip into a cell culture perfusion chip. The chip is adaptable due to the flexibility of the EO pumps to work as both pressure sources and virtual valves for regulating the fluid flow. Experiments with rainbow trout gill cells (RT-gill W1) were performed in order to validate the use of EO pumps for cell culture. Results show that the cells are not affected by the presence of the EO pumps as the electric field is isolated from the cells. However, the pumps were only able to operate continuously for eight hours before electrolysis effects stopped fluid flow. As a proof of concept, this shows that it is feasible to use EO pumps within a cell culture network.

Continuous perfusion cell culture chips offer the biomedical researcher unprecedented control over the microenvironment surrounding the cell which is not feasible with conventional static cell culture procedures. Applying microfluidics technology to these devices provides several benefits including increased fluid and media control, reduced consumption of reagents, continuous monitoring of cells and the potential for massively parallel experiments. In this work a new continuous perfusion cell culture chip is studied that utilizes electroosmotic pumping to control fluid flow. Problems associated with EOF and cells are solved by incorporating electroosmotic pumps (EO pumps) which generate an induced pressure driven flow in regions with cells. Several advantages of EO pumps include pulse free flow, quick flow control and precise movement of minute volumes of fluid. However, the high salt concentration in cell culture medium creates significant problems for EO pumps such as decreased flow rate due to low zeta potential, increased electrolysis due to large current draw, significant joule heating, bubble formation and polarization. Attempts to solve these problems with the proposed microfluidic chip are discussed. The microfluidic chip is fabricated using soft lithography techniques developed as part of this work. The designs were modelled using a combination of numerical simulations with a commercial software program and compact circuit modelling. The pumps were integrated on-chip into a cell culture perfusion chip. The chip is adaptable due to the flexibility of the EO pumps to work as both pressure sources and virtual valves for regulating the fluid flow. Experiments with rainbow trout gill cells (RT-gill W1) were performed in order to validate the use of EO pumps for cell culture. Results show that the cells are not affected by the presence of the EO pumps as the electric field is isolated from the cells. However, the pumps were only able to operate continuously for eight hours before electrolysis effects stopped fluid flow. As a proof of concept, this shows that it is feasible to use EO pumps within a cell culture network.

Conventional cell cytometers are often bulky and thus not convenient for bio-medical analysis where portable devices are desired. They also suffer from the drawback of high cost due to the complicated and expensive optical detection system involved. Therefore miniaturizing conventional cell cytometer is highly demanded as it offers an opportunity to transform the conventional bulky systems to more cost-efficient and portable microfluidic cell sorting devices. In addition to the advantages reduced cost and enhanced portability, microfluidic cell sorting devices require only a tiny amount of sample for analysis. In this thesis, one common microfluidic cell sorting device is developed using similar conventional functions and concepts but different sorting method. Unlike most of the conventional cell cytometers in which an electrical field or magnetic field is employed to deflect the charged target cells to the collecting container, microfluidic cell sorting devices use the fluid flow to control the movement of the targeted cells to the collecting reservoir. By using an electroosmitic pump, the response time of the flow switch is significantly lowered, leading to a much higher sorting efficiency. Despite the advantages of microfluidic cell sorting devices, there are some issues need to be addressed before realization of such devices. For example, more studies are required on the successful integration of the optical elements in the devices. In microfluidic, the transport phenomena is also different from that in macroscopic. Unlike that in macroscopic, surface forces are important in microfluidics. They result in pressure-induced flow which gives the parabolic profile of the velocity along the channel. Also, a plug-like velocity which is generated by the electoosmitic flow is required for the more controllable and accurate detection. To suppress the pressure-driven flow, hydro-resistance elements (Shallow channel network) are implemented on the microfluidic devices. Fabrication of optical elements by deposition of optical materials on glass or silicon wafer has been reported. However, this Micro Electro-Mechanical (MEM) technique requires special equipment and cleanroom facilities used in the semiconductor industry. A good alternative to the MEMS technique is soft lithography where optical elements can be created using polymers. In this work, ultraviolet-sensitive photo resists SU8 is used to fabricate the microfluidic cell sorting devices and the optical elements. By using the mask with the patterns of the microchannel network and optical elements, the optical elements can be fabricated with the microchannel, eliminating the problem of alignment. Experiments are also conducted to evaluate the integrated optical elements. To prevent cross-contamination, samples are usually prepared and are only mixed inside the microfluidic devices by the embedded mixers. Such embedded mixers, however, pose a great challenge as the small characteristic length of a microfluidic device tends to give a laminar flow and diffusion-dominated mixing. A simple passive micromixer is investigated to find the possibilities to integrate it to the microfluidic devices. To truly understand the diffusional mixing, a Y channel mixer is studied through the numerical and experimental investigations. Based on the results found, a possible design is also proposed and evaluated by experiments.

Many applications for the analysis and processing of biological materials require the enrichment of cell subpopulations. Conventional cell sorting systems are large and expensive with complex equipment that necessitates specialized personnel for operation. Employing microfluidics technology for lab-on-a-chip adaptation of these devices provides several benefits: improved transport control, reduced sample volumes, simplicity of operation, portability, greater accessibility, and reduced cost. The designs of microfluidic cell sorting chips vary widely in literature; evaluation and optimization efforts are rarely reported. This study intends to investigate the primary components of the design to understand the effect of various parameters and to improve the performance of the microfluidic chip. Optimized individual elements are incorporated into a proposed cell sorter chip with the ability to dynamically sort target cells from a non-homogeneous solution using electrical driving forces. Numerical and experimental results are used to evaluate the sample focusing element for controlled cell dispensing, the sorting configuration for target cell collection, and the flow elements for reduced pressure effects and prevention of flow blockages. Compact models are adapted to solve the potential field and flow field in the chip and to predict the focused sample stream width. A commercial CFD package is used to perform 2-D simulations of the potential, velocity, and concentration fields. A fluorescence microscopy visualization system is implemented to conduct experiments on several generations of chip designs. The data from sample focusing experiments, performed with fluorescent dye samples, is analyzed using a Gaussian distribution model proposed in this work. A technique for real-time monitoring of fluorescent microspheres in the microfluidic chip enables the use of dynamic cell sorting to emulate fully autonomous operation. The performance values obtained from these experiments are used to characterize the various design configurations. Sample focusing is shown to depend largely on the relative size of the sheath fluid channel and the sample channel, but is virtually independent of the junction shape. Savings in the applied potential can be achieved by utilizing the size dependency. The focusing performance also provides information for optimizing the widths of the channels relative to the cell size. Successful sorting of desired cells is demonstrated for several designs. Key parameters that affect the sorting performance are discussed; a design employing the use of supplemental fluid streams to direct the particle during collection is chosen due to a high sorting evaluation and a low sensitivity to flow anomalies. The necessary reduction of pressure influences to achieve reliable flow conditions is accomplished by introducing channel constrictions to increase the hydrodynamic resistance. Also, prolonged operation is realized by including particle filters in the proposed design to prevent blockages caused by the accumulation of larger particles. A greater understanding of the behaviour of various components is demonstrated and a design is presented that incorporates the elements with the best performance. The capability of the microfluidic chip is summarized based on experimental results of the tested designs and theoretical cell sorting relationships. Adaptation of this chip to a stand-alone, autonomous device can be accomplished by integrating an optical detection system and further miniaturization of the critical components.

Conventional cell cytometers are often bulky and thus not convenient for bio-medical analysis where portable devices are desired. They also suffer from the drawback of high cost due to the complicated and expensive optical detection system involved. Therefore miniaturizing conventional cell cytometer is highly demanded as it offers an opportunity to transform the conventional bulky systems to more cost-efficient and portable microfluidic cell sorting devices. In addition to the advantages reduced cost and enhanced portability, microfluidic cell sorting devices require only a tiny amount of sample for analysis. In this thesis, one common microfluidic cell sorting device is developed using similar conventional functions and concepts but different sorting method. Unlike most of the conventional cell cytometers in which an electrical field or magnetic field is employed to deflect the charged target cells to the collecting container, microfluidic cell sorting devices use the fluid flow to control the movement of the targeted cells to the collecting reservoir. By using an electroosmitic pump, the response time of the flow switch is significantly lowered, leading to a much higher sorting efficiency. Despite the advantages of microfluidic cell sorting devices, there are some issues need to be addressed before realization of such devices. For example, more studies are required on the successful integration of the optical elements in the devices. In microfluidic, the transport phenomena is also different from that in macroscopic. Unlike that in macroscopic, surface forces are important in microfluidics. They result in pressure-induced flow which gives the parabolic profile of the velocity along the channel. Also, a plug-like velocity which is generated by the electoosmitic flow is required for the more controllable and accurate detection. To suppress the pressure-driven flow, hydro-resistance elements (Shallow channel network) are implemented on the microfluidic devices. Fabrication of optical elements by deposition of optical materials on glass or silicon wafer has been reported. However, this Micro Electro-Mechanical (MEM) technique requires special equipment and cleanroom facilities used in the semiconductor industry. A good alternative to the MEMS technique is soft lithography where optical elements can be created using polymers. In this work, ultraviolet-sensitive photo resists SU8 is used to fabricate the microfluidic cell sorting devices and the optical elements. By using the mask with the patterns of the microchannel network and optical elements, the optical elements can be fabricated with the microchannel, eliminating the problem of alignment. Experiments are also conducted to evaluate the integrated optical elements. To prevent cross-contamination, samples are usually prepared and are only mixed inside the microfluidic devices by the embedded mixers. Such embedded mixers, however, pose a great challenge as the small characteristic length of a microfluidic device tends to give a laminar flow and diffusion-dominated mixing. A simple passive micromixer is investigated to find the possibilities to integrate it to the microfluidic devices. To truly understand the diffusional mixing, a Y channel mixer is studied through the numerical and experimental investigations. Based on the results found, a possible design is also proposed and evaluated by experiments.