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Title: Hybrid devices for lab-chip chromatography and droplet-based microfluidics
Author: Kim, Jin-Young
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Recent years have seen considerable interest in the use of microfabricated systems in chemical and biological due to their significant advantages in terms of speed, analytical throughput, yield, unit cost, footprint, reagent requirements and control. Inevitably this has led to a growing interest in transferring chromatographic methods to planar chip formats since techniques using high performance LC play such a prominent role in modern bioanalysis. In addition, the manipulation of multiphase (or segmented) flows within microfluidic channels has been recently investigated as a promising approach for large-scale experimentation in biology and chemistry. Importantly, flow segmentation allows for the compartmentalisation of reagent volumes ranging from a few femtolitres to hundreds of nanolitres within a continuous and immiscible fluid, the production of monodisperse droplets at high frequencies, the accurate control of droplet contents and the ability to perform kinetic analysis with high precision. Accordingly the integration of droplet-based microfluidics with HPLC has the potential to dramatically reduce dispersion and minimise dead volume effects by using droplets to collect fractions of the column effluent. This basic progress preserves the chemical identity of each fraction allowing further analysis downstream. In this work, microfluidic devices were fabricated using thermoset polyester (TPE) to operate under high pressure which is required for LC separation and high frequency droplet generation. The optical characteristics of the fabricated devices were assessed for feasibility of optical detections for droplets. Substrate resistance to pressure also was investigated for droplet generation with high frequency. Lastly, droplets were generated under various conditions by adjusting flow-rates and the oil viscosity. Secondly LC separation columns were formed in TPE channels using two different column materials: particulate and polymer monolithic columns. The packed channels were investigated by SEM. In addition, permeability was calculated from back25 pressures measured as a function of flow-rates and compared with columns. Neurotransmitters were separated by the columns to estimate performance. Thirdly, the both operations, LC separation and droplet-based microfluidics, were combined in a single planar format. Sequential operations of separation, compartmentalisation and concentration gradient generation were integrated on a single chip and characterised using confocal laser-induced fluorescence detection. Finally, a preliminary investigation is reported into the possibility of the indirect electrochemical detection as a universal detection that can monitor electrochemically detectable samples as well as non- or less-electroactive bio samples. Amino acids were separated by a commercial RPHPLC column and detected indirectly.
Supervisor: O'Hare, Danny Sponsor: Global Research Laboratory, South Korea
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral