Effect of electrodes positions on the performance of microfluidic enzymatic biofuel cell: From two streams to a single-stream flow device

Abstract

Membraneless microfluidic enzymatic biofuel cells (μEBFCs) operated under the co-laminar flow of fuel and oxidant often face cross-mixing issues, especially at low flow rates. In this work, we propose a new approach to design the single-stream μEBFC based on the investigation of relative positions of the electrodes at the top and bottom of the microchannel. To achieve this, a μEBFC was fabricated with multiwalled carbon nanotube (MWCNT) electrodes via a stencil method. The bioanode and biocathode were modified with glucose dehydrogenase and laccase via direct covalent bonding, respectively. The best results were attained by placing the cathode at the top and anode at the bottom of the microchannel in a Y-shaped two streamflow μEBFC. When a single electrolyte stream was used to achieve more practicality and ease of use, the performance was reduced by 40%. However, with the new design of electrodes in single-stream μEBFC, i.e. cathode at the top and anode at the bottom facing each other in the microchannel, the performance was recovered by 20%. This corresponds to maximum current and power density of 216 ± 12 μA cm−2 and 69.2 ± 9.2 μW cm−2, respectively. The stacking ability of the device was realized by connecting the two cells in series and parallel. The maximum power density delivered by the two single-stream μEBFCs’ stack reached 160 μW cm−2 at 0.3 V. Thus, this study validates the viability of using single-stream μEBFCs in large stacks to power microelectronics more simply and practically.