Bridging biochemistry and microengineering: glucose oxidation in microfluidic biofuel cells with carbon-MEMS and conductive polymers electrodes

Abstract

Microfluidic biofuel cells are promising power sources for small-scale devices. Its construction is simple and requires low-cost materials. We report four glucose/O2 microfluidic enzymatic biofuel cells consisting in a double-Y-shaped microchannel and based on Carbon Micro Electro Mechanical Systems (C-MEMS) electrodes to test the composite poly(3,4-ethylene dioxythiophene)–poly(gallic acid) (PEDOT-PGAL) conducting polymer as an electroactive layer for enzyme immobilization. The following microfluidic enzymatic biofuel cells were microfabricated to compare their performances: 1) glucose/O2 using bioelectrodes, 2) glucose/O2 using glucose oxidase and Laccase, in solution, 3) glucose/hydrogen peroxide using bioelectrodes, and 4) glucose/hydrogen peroxide using glucose oxidase and horseradish peroxidase, in solution. The use of these two classes of materials, C-MEMS electrodes and conducting polymer inks, offers an advantageous interface for biomolecular electron transfer owing to the rich organic chemistry of the carbon interfaces. On the other hand, the conducting polymer PEDOT-PGAL acts as an electroactive layer for straightforward applications suitable for batch fabrication. All the studied cells presented positive electromotive forces and the discharge behavior of a fuel cell, yielding similar power densities. As expected, the cells that used enzymes in solution delivered higher power densities, but these values are dependent on the flow rate, while cells with immobilized enzymes present a more stable maximum power output. To our knowledge, this is the first report of an electrode system based on pyrolytic carbon/PEDOT-PGAL applied in a microfluidic enzymatic biofuel cell.