Development and characterisation of macro-disc and micro-band electrodes for electrochemical sensing applications
The aim of this PhD thesis was to investigate potential next generation sensor platforms for electrochemical biosensor developments, specifically towards health monitoring applications. With increasing interest in the integration of miniaturised electrodes with minimally invasive and wearable devices, this thesis sought to explore electrodes fabricated using three different technologies for the construction of electrochemical biosensors: Silicon microfabrication, Laser scribing, and dispense printing. The first experimental section aimed to investigate the use of a single ultramicroband electrode fabricated on silicon for mediator-free glucose monitoring in bio-fluid environments. Six ultramicroband electrodes, a counter electrode and reference electrode were fabricated using standard microfabrication methods i.e. lithography and etching techniques. Glucose oxidase was selected as a model enzyme to attach onto a platinum modified gold microband electrode by electropolymerisation with an o-phenylenediamine/ß-cyclodextrin layer. The resulting microband biosensor demonstrated on-chip glucose detection in buffer based media. When applied to foetal bovine serum the sensor displayed a reduced sensitivity. The second experimental section explores the use of laser-scribed graphitic carbon for flexible sensing applications. A facile fabrication method was assessed involving electrodeposition of platinum followed by two casting steps to functionalise electrodes. This study examined the chronoamperometric response of the enzymatic lactate sensor whilst the flexible polyimide substrates were fixed at a curvature (K) of 0.14 mm-1. No noticeable change in signal response was observed in comparison to calibrations obtained with a flat substrate (K=0 mm-1), suggesting potential opportunities for sensor attachment or integration with oral-care products such as mouth swabs and mouth guards. Both laser scribed graphitic carbon and Ag/AgCl modified-laser scribed graphitic carbon were examined as reference electrodes for chronoamperometric lactate measurements. This device was applied for measuring lactate concentrations in artificial saliva and diluted sterile human serum. Finally, this study investigates the potential for a low cost additive printing tool to enable the fabrication of electrochemical sensor devices. To do this, electrodes were designed and printed onto polyimide substrates. Reproducibility between electrode dimensions was assessed using 3D microscopy. Standard electrochemical characterisation techniques were employed to study the reproducibility between electrode electrochemical response. Functionality was also assessed whilst electrodes were fixed were fixed at a curvature (K) of 0.14 mm-1. Finally, a simple casting approach was applied to the dispense printed working electrode to construct a lactate biosensor for a proof of concept electrochemical sensor demonstration.
Flexible sensors, Microbands, Lactate sensing, Glucose sensing, Additive printing, Electrochemical biosensor, Laser scribing
Networked Digital Library of Theses and Dissertations