AbstractSince the first implantation of a cardiac pacemaker numerous efforts have been made to develop miniature implantable power devices, which would be able to run continuously for long periods of time without the need for replacement. In this context enzymatic biofuel cells (EBFCs) represent an attractive alternative, as they work at body temperature, are light and easy to miniaturise. Additionally, enzymatic biofuel cells can generate energy from the metabolites already present in physiological fluids, and produce waste products that naturally occur in the human body. With a view to improving the biocompatibility of such devices, the use of highly porous gold (hPG) as a non-toxic high surface area alternative to the carbon nanotube based materials currently used was here investigated. The process for directly depositing hPG onto conductive surfaces was further developed to improve the stability of the deposited hPG films. The possibility of depositing these films on a range of different materials was also investigated. In particular it was shown that hPG films could also be deposited on very low cost materials, such as graphite composites. It was also demonstrated that these hPG electrodes exhibited potential for the direct electro-oxidation of aldehyde group containing sugars. The potential use of hPG electrodes as abiotic glucose sensors was consequently investigated and found to give stable amperometric responses between 0 and 50 mM, with a strong glucose dependant response even at the lowest concentration investigated of 0.5 µM. However, since hPG electrodes were found to be susceptible to a large degree of interference and fouling in biological solutions, the use of glucose oxidase (GOx) on hPG electrodes was investigated in order to increase the specificity and stability of such electrodes in biological systems. A rapid and simple technique for the direct and functional deposition of GOx onto hPG was developed without using foreign electron mediators. These hPG-GOx electrodes were found to act as glucose sensors with extremely high sensitivity (22.7 µA mM-1 cm-2), and a linear response to glucose in a range of between 50 μM and10 mM. Finally EBFCs that exhibit continuous flow through were developed using fast prototyping techniques that employ 3D printed moulds. These EBFCs employed hPG-GOx electrodes coupled with hPG and laccase electrodes in order to generate power from glucose. The continuous and stable power production from a flow through EBFC for up to 30 days was subsequently demonstrated for the first time, with a peak power output of approximately 2 µW.
|Date of Award||20 Mar 2015|
|Supervisor||Mirella Di Lorenzo (Supervisor) & Frank Marken (Supervisor)|
Development of Miniature Enzymatic Biofuel Cells as Potential Power Sources for Implantable Medical Devices:
Du Toit, H. (Author). 20 Mar 2015
Student thesis: Doctoral Thesis › PhD