Microfluidic fuel cell.

摘要

Microfluidic fuel cells exploit the lack of convective mixing at low Reynolds number to eliminate the need for a physical membrane to separate fuel from oxidant. One of the issues in the development of microfluidic fuel cells is to understand the transport characteristics of fuel and oxidants. Similar to conventional fuel cells, the catalytic consumption of fuel and oxidant at respective electrode creates depleted region of reactants, ie, the diffusion layer, next to the electrode. The convective nature of the flow above the electrode in a microfluidic fuel cell, however, affects the rate at which fuel gets depleted in the diffusion layer. The interplay between convective flow and diffusion layer along an electrode, therefore, offers a different perspective when it comes to designing microfluidics fuel cell compared to that of conventional fuel cell.;Low utilization rate of the reactants is another key challenge that is faced in microfluidic fuel cell. Increasing the flow rate at which reactants are delivered into the microchannel increases the rate of mass transport of the reactants to the electrode, thereby increases current output. Increasing the flow rate, however, reduces the residence time of the reactants in the microchannel. Consequently, the percentage of the reactants that are being utilized by the electrodes are reduced, causing a drop in the utilization rate of the reactants.;In this thesis, the effects of diffusion layer on the performance of microfluidic fuel cell will be investigated. Subsequently, an active means of controlling the growth of the diffusion layer along the electrode by linearly reducing the height of the microchannel, using a rapid prototype technique, is discussed. An analytical solution for the mass transport limited current for the microchannel of linearly descending height is also derived and its theoretical value is compared with experimental results. To address the issue of low utilization rate of reactants, a novel fabrication method will be presented to improve the utilization rate without compromising on the current output. Last but not least, a microfluidics microbial biofuel cell with an air breathing cathode, with fuel and oxidant operating in the same compartment, is also discussed.