Modelling microelectrode and microbiosensor responses through computer simulation

The work in this thesis has involved the modelling of inlaid and recessed microdisc electrode systems through numerical simulation. Transient responses are modelled using the finite element method for the mass transport limited situation. The chronoamperometric response is better than 1% accurate for the inlaid microdisc. The chronoamperometric response for the recessed microdisc is validated in the steady state region and expressions are developed to describe the diffusion limited behaviour.The catalytic EC' behaviour has been invstigated through simulation for the inlaid and recessed microdisc electrodes. Expressions have been developed to describe the steady state current behaviour for any pseudo first order EC' rate constant and for shallow recess depths.The homogeneous enzyme system of a glucose biosensor (FcCOOH / GOx / Glucose system) has been studied experimentally and through simulation for the chronoamperometric response at inlaid microdisc electrodes. The effect of rate constants, mediator and substrate concentrations and microdisc radii size have been studied. Further insight into the behaviour of the systems has been gained through a detailed analysis for the concentration and reaction profiles. A theoretical treatment is presented for the steady state current at an inlaid microdisc over a range of substrate concentrations for the mediator / enzyme / substrate system. An initial case diagram study has been carried out for the inlaid microdisc under saturating substrate kinetics. Limitations in solving the non-linear kinetics at microelectrode geometries are also discussed.The homogeneous enzyme system has also been studied using a recessed microdisc electrode. The benefits of this electrode geometry are discussed.Initial studies into the dissolution of mediator from a commercially available MediSense glucose electrode is described.