Fabrication of Enzymatic Biofuel Cell with Electrodes on Both Sides of Microfluidic Channel

Enzymatic biofuel cells (EBFCs) that utilize glucose as fuel in a human body to produce electricity are being explored as promising alternatives to power implantable devices. However, some limitations need to be overcome to render such micro-electronic devices practically applicable. Here, we propose a microfluidic EBFC architecture with electrodes on both sides of the microchannel and its fabrication via stencil method. Multiwalled carbon nanotube (MWCNT) electrodes are fabricated on both sides of a Y-shaped microfluidic channel to reduce the effect of the depletion boundary layer and cross-diffusional mixing of the fuel and oxidant, which are functions of the distance from the microchannel inlet. Therefore, the microchannel length is reduced by half, while maintaining the same MWCNT electrode area. The microchannel is produced by polydimethylsiloxane (PDMS) casting whereas the electrodes are fabricated by a PDMS stencil, using MWCNT patterned on etched indium tin oxide glass. The electrodes are modified with glucose oxidase and laccase via direct covalent bonding. The cell performance is studied at different microchannel heights and flow rates, obtaining a maximum power and current density of 153 µW cm⁻² and 450 µA cm⁻², respectively, at a microchannel height of 450 µm and flow rate of 25 mL h⁻¹. The double-layer EBFC shows a 23% improvement in the performance compared to a single-layer EBFC.