Feasibility Study of Energy Harvesting via Biofuel Cell for Miniaturised Implantable Biosensors

In the current pursuit of sustainable energy, biofuel cells are attracting considerable attention. Within biomedical engineering, the concept of harnessing energy from biological fluids, such as blood, holds significant promise, enabling both full autonomy and miniaturisation. In this context, this study aims to identify the most efficient biofuel cells for miniaturised implantable biosensors and design a prototype based on the obtained results. To achieve this goal, a systematic literature review was conducted, comparing biofuel cells based on relevant parameters for powering devices, including power density and operative voltages. This categorisation guided material selection, considering a cost-performance trade-off. Carbon nanotubes and Laccase were chosen to facilitate oxygen reduction at the cathode. In contrast, carbon nanotubes with Glucose Oxidase (with and without ferrocenemethanol) played a similar role at the anode, where glucose proved to be the most advantageous fuel. Electrode functionalisation and assessment involved electrochemical and morphological analyses, culminating in the recording of preliminary results for the biofuel cell prototype. The analysis of scientific literature revealed that under physiological conditions, including pH, glucose concentration, and single-chamber biofuel cells, the maximum power density obtained was 1 mW/(cm^2 ) at 0.65 V. The use of nanomaterials, such as carbon nanotubes, and enzymes proved to be crucial by enhancing electron transfer, increasing the effective area, and introducing specificity to each electrode, enabling the biofuel cell to operate without the need for a membrane. During the design phase, the functionalisation of the cathode highlighted the critical role of oxygen, which has a limited concentration in the solution. At the anode, the attempt to achieve mediated electron transfer proved successful, in contrast to the method of direct electron transfer. Finally, the characterisation of the biofuel cell demonstrated a preliminary power generation of 0.38 μW/(cm^2 ) at 0.2 V in 500 mM glucose. The preliminary development of the prototype confirms the feasibility of generating energy with the selected materials and highlights its limitations, laying the foundation for its optimization, such as through a more robust stabilization method. Furthermore, the project proves valuable in the context of active medical device development, enabling a comparison between the requirements of hypothetical implantable sensors and cutting-edge technology.