Development of an integrated complex 3D fluidic device assembled from fully characterised functional blocks: Michaelis-Menten enzyme kinetics analysis as a case study

Abstract

The work presented in this thesis demonstrates a new approach to the design of integrated uidic devices. Most `lab-on-a-chip' are in fact `chips-in-a-lab'. The equipment used to operate them, such as microscopes and syringe pumps, is bulky, expensive and the portability is non-existent. Fluidic devices operate on multiple domains, such a fludics, pneumatics, sensing, control, etc. By integrating the domains to a single device, cost can be reduced and portability increased. A new manufacturing process was developed to allow for the integration of multiple domains. The vast majority of fluidic devices are two-dimensional, made via soft lithography, which limits the complexity and integration of other components. Three- dimensional fluidic devices can be used to create complex intricate networks and can include sensors, actuators and optics. A negative mould was 3D printed in Acrylonitrile Butadiene Styrene (ABS), encased in Polydimethylsiloxane (PDMS) before being placed in an acetone bath. Because of the swelling properties of ABS in solvents, Acetone could reach the embedded ABS. ABS was liquefied in the presence of acetone, making it possible to be flushed from the PDMS, leaving a void. Following the development of the manufacturing process, functional fluidic blocks were developed to create more complex devices based on usage. Each block was designed to perform a given task, including a photometric sensor, a proportional valve, a turbulent flow mixer, and storage wells. Using the blocks that were developed, a device designed to perform Michaelis-Menten enzyme kinetics analysis was demonstrated. The device was operated by a combination of a custom PCB and a Matlab GUI, thus creating an integrated system. Enzyme kinetics were analysed by determining the initial reaction rate of the enzyme-catalysed reactions for various concentration of its substrate. In order to determine reaction rates, it is common to monitor the opacity of the reaction product over time. This is often achieved by using a substrate (or a substrate analogue) which produces a product with a unique optical absorbance, thus the opacity of the product can be monitored by absorption spectroscopy. The experiment was repeated for multiple concentrations before the kinetics were extrapolated. The device created can perform the same task, as well as automating the mixing of any concentration necessary for the kinetic analysis, at fraction of the cost of commercial equipment.