The introduction of bio-molecules into cells and embryos is required in the fields of drug development, genetic engineering and in-vitro fertilization. It has been applied to create transgenic mammals and to improve pest and mold resistance in plants. However, the efficient transfection of materials still poses a problem, and a variety of techniques, broadly classified as biochemical and physical means, are actively being developed. One technique that is promising is capillary microinjection as it offers low cytotoxicity, targeted injections and high transfection efficiency. However, this process suffers from low throughput and variability as it is an operator mediated process. Other problems associated with capillary microinjection are limitations on the minimum needle size and variability in transfected volumes due to the use of pressure driven flow for injections. In this thesis we propose a device that employs microfluidic principles to enable cell microinjections in a 'lab on a chip' format and eliminates the problems associated with capillary microinjection. The device is fabricated using poly dimethylsiloxane (PDMS) rapid prototyping and features two separate channel structures-one to supply the targets and the other to supply the reagent. Integrated into the device are a microinjection capillary (10 μm tip diameter) and a suction capillary (0.5mm ID/1mm OD) which is used to immobilize the targets in the channel prior to injection. The actuation of the injection needle into the targets is achieved by the compliant deformation of the flexible PDMS substrate as a result of an externally applied displacement. This is made possible by the selective reinforcement of the PDMS substrate. From testing it was found that the effective needle actuation is 83.8% of the externally applied displacement. The injections occur in a planar configuration therefore providing precise control over the location of injection. Furthermore, the mechanism requires only one degree of freedom to perform injections, and therefore greatly simplifies existing injection techniques which require orientation in a three dimensional space. The limitations of the use of pressure driven flow for injections are overcome by performing reagent injection by electroosmotic flow, which is induced by applying a potential to electrodes embedded in the target and reagent supply channels. The applied potential induces electroosmotic flow through the embedded needle and into the injection target. This provides precise electrical dosage control. The flow rates were obtained by measuring the velocity of the interface between a neutral fluorescent marker and a clear pH 10 buffer solution. The obtained flow rates follow a predictable linear trend and correspond well to theory. The use of electroosmotic flow enables the use of smaller injection needles as it scales more favorably (r^-2) than pressure driven flow (r^-4) and becomes increasingly dominant in smaller dimensions. Present pressure microinjection systems are limited to injection needles with tip diameters larger than 0.2μm due to the high pressures required to dose at smaller dimensions. All components of the device are fully scalable and enable further miniaturization, multiple parallel injections and autonomous functionality. The device requires smaller volumes of samples and expensive reagents and also reduces the time required for performing injections. Overall, it device maintains the advantages of microinjection, while eliminating problems of low throughput, dosage control and restrictions on the injection needle size. The device was successfully used and characterized for the injection of single-cell Xenopus Laevis eggs and Zebrafish embryos. / Thesis / Master of Applied Science (MASc)

In present finite element study, the dynamics of incompressible isothermal flows of Newtonian and two generalised non-Newtonian models through complex mixing-separating planar channel and circular pipe filled with and without porous media, including Darcy's term in momentum equation, is presented. Whilst, in literature this problem is solved only for planar channel flows of Newtonian and viscoelastic fluids. The primary aim of this study is to examine the laminar flow behaviour of Newtonian and inelastic non-Newtonian fluids, and investigate the robustness of the numerical algorithm. The rheological properties of non-Newtonian fluids are defined utilising a range of constitutive equations, for inelastic non-Newtonian fluids non-linear viscous models, such as Power Law and Bird-Carreau models are used to capture the shear thinning behaviour of fluids. To simulate such complex flows, steady-state solutions are sought employing time-dependent finite element algorithm. Temporal derivatives are discretised using second order Taylor series expansion, while, spatial discretisation is achieved through Galerkin approximation in combination to deal with incompressibility a pressure-correction scheme adopted. In order to achieve the algorithm of semi-implicit form Darcy's-Brinkman equation is utilized for the conversion in Darcy's terms and diffusion, while Crank-Nicolson approach is adopted for stability and acceleration. Simple and complex flows for various complex flow bifurcations of the combined mixing-separating geometries, for both two-dimensional planar channel in Cartesian coordinates, as well as axisymmetric circular tube in cylindrical polar coordinates system are investigated. These geometries consist of a two-inverted channel and pipe flows connected through a gap in common partitions, initially filled with non-porous materials and later with homogeneous porous materials. Computational domain is having variety it has been investigated with many configurations. These computational domains have been appeared in industrial applications of combined mixing and separating of fluid flows both for porous and non-porous materials. Fully developed velocity profile is applied on both inlets of the domain by imposing analytical solutions found during current study for porous materials. Numerical study has been conducted by varying flow rates and flow direction due to a variety in the domain. The influence of varying flow rates and flow directions are analysed on flow structure. Also the impact of increasing inertia, permeability and power law index on flow behaviour and pressure difference are investigated. From predicted solution of present numerical study, for Newtonian fluids a close agreement is realised between numerical solutions and experimental data. During simulations, it has been noticed that enhancing fluid inertia (flow rates), and permeability has visible effects on the flow domains. When the Reynolds number value increases the size and power of the vortex for recirculation increases. Under varying flow rates an early activity of vortex development was observed. During change in flow directions reversed flow showed more inertial effects as compared with unidirectional flows. Less significant influence of inertia has been observed in domains filled with porous media as compared with non-porous. The power law model has more effects on inertia and pressure as compared with Bird Carreau model. Change in the value of permeability gave significant impact on pressure difference. Numerical simulations for the domain and fluids flow investigated in this study are encountered in the real life of mixing and separating applications in the industry. Especially this purely quantitative numerical investigation of flows through porous medium will open more avenues for future researchers and scientists.