Development of an autonomous lab-on-a-chip system with ion separation and conductivity detection for river water quality monitoring

Joly, Etienne Pierre

Engineering
December 2013

Thesis or dissertation


Rights
© 2013 Etienne Pierre Joly. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
Abstract

This thesis discusses the development of a lab on a chip (LOC) ion separation for river water quality monitoring using a capacitively coupled conductivity detector (C⁴D) with a novel baseline suppression technique.

Our first interest was to be able to integrate such a detector in a LOC. Different designs (On-capillary design and on-chip design) have been evaluated for their feasibility and their performances. The most suitable design integrated the electrode close to the channel for an enhanced coupling while having the measurement electronics as close as possible to reduce noise. The final chip design used copper tracks from a printed circuit board (PCB) as electrodes, covered by a thin Polydimethylsiloxane (PDMS) layer to act as electrical insulation. The layer containing the channel was made using casting and bonded to the PCB using oxygen plasma. Flow experiments have been conduced to test this design as a detection cell for capacitively coupled contactless conductivity detection (C⁴D).

The baseline signal from the system was reduced using a novel baseline suppression technique. Decrease in the background signal increased the dynamic range of the concentration to be measured before saturation occurs. The sensitivity of the detection system was also improved when using the baseline suppression technique. Use of high excitation voltages has proven to increase the sensitivity leading to an estimated limit of detection of 0.0715 μM for NaCl (0.0041 mg/L).

The project also required the production of an autonomous system capable of operating for an extensive period of time without human intervention. Designing such a system involved the investigation of faults which can occur in autonomous system for the in-situ monitoring of water quality. Identification of possible faults (Bubble, pump failure, etc.) and detection methods have been investigated. In-depth details are given on the software and hardware architecture constituting this autonomous system and its controlling software.

Publisher
Department of Engineering, The University of Hull
Supervisor
Bell, Ian M.; Greenway, Gillian M.; Haswell, S. J. (Stephen John), 1954-
Sponsor (Organisation)
Engineering and Physical Sciences Research Council
Grant number
EP/G014221/1
Qualification level
Doctoral
Qualification name
PhD
Language
English
Extent
11 MB
Identifier
hull:12420
QR Code