Novel fabrication techniques for microfluidic based in-situ oceanographic nutrient sensors

Abstract

This work presents an investigation into the production of components for in-situ oceanographic nutrient sensors. These devices are based on a micro fluidic chip platform, taking the lab-on-a-chip (LOC) system concept out of the laboratory and into a real world environment. The systems are designed to provide data on nutrient concentrations in the ocean and as such are built from robust low cost materials designed for deployments from 24 hours to 3 months. This report focuses on the challenges faced in designing a micro fluidic system for these harsh deployment situations including a study of the relevant literature to indicate short falls in current technologies.

The aim of this work was to develop the next generation of micro fluidic chip based nutrient sensors. A novel solvent vapour bonding technique has been developed for the production of polymer based micro fluidic chips which produces robust chips while simultaneously reducing the surface roughness of the substrates during bonding. This has allowed micromilling of polymer substrates to quickly and easily develop new chip designs with optical quality features. The surface reduction technology has enabled development of a method to integrate absorbance cells into tinted PMMA devices which is also discussed. Integration of polymer membranes to produce valve and pump structures is discussed and a novel bonding technique for chemically robust Viton R membranes is demonstrated. The final chapter includes a discussion on system topologies, concentrating on the need for high resolution sampling and the implications on system design that arise. A novel multiplexed stop flow system is demonstrated. Questions about the role of traditional micro fluidic components, such as mixers, in high-throughput low temporal response system designs are discussed and a micro fluidic mixer suitable for some of these systems demonstrated.

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Identifiers

ORCID for M. Mowlem: orcid.org/0000-0001-7613-6121

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