Monolithic integration of proton exchange membrane microfuel cells

Proton Exchange Membrane Fuel Cells (PEMFCs) and Direct Methanol Fuel Cells (DMFCs) become promising because they potentially offer 5-10 times greater energy densities than rechargeable batteries, and are able to replace the tedious recharging by instant fuel refilling. Monolithic integration of fuel cells is necessary for applications with extremely limited form factor, such as wireless sensor nodes, etc. In this work, critical integration issues, including the integration of high surface area silicon-based fuel cell electrode, monolithic serial connection of fuel cell arrays, and the key fabrication techniques for further integration of fuel cells, were addressed.;A silicon-based PEMFC electrode architecture was proposed to integrate high active surface area catalysts. The electrode structure is a general platform in which surface texturing technologies can be applied to enhance the surface area without increasing the electrode resistance. Catalysts can be applied using dry deposition methods such as sputtering, or using electrodeposition methods.;In order to boost voltage output, planar configuration was adopted to implement serially connected monolithic fuel cell arrays. High surface area catalysts were selectively deposited on the anode and cathode. An analytical model was proposed to model the electrode efficiency as well as to optimize the electrode dimensions. An equivalent circuit model was proposed to model the crosstalk effect between connected fuel cells.;Architecture for further integration of micofuel cells was proposed, and the key fabrication techniques to implement the structures were investigated. A maskless process to create silicon nanopores and nanopillars using deep reactive ion etching (DRIE) was developed. The dependence of the etching results on initial surface morphology and masking materials was studied. Sacrificial surface technology to form deep buried channel was developed and demonstrated. The maskless dry etching technology and the deep buried channel formation technology make the implementation of the structures required by the proposed architecture possible.