Evaluation of single and stack membraneless enzymatic fuel cells based on ethanol in simulated body fluids

The purpose of this work is to evaluate single and double-cell membraneless microfluidic fuel cells (MMFCs) that operate in the presence of simulated body fluids SBF, human serum and blood enriched with ethanol as fuels. The study was performed using the alcohol dehydrogenase enzyme immobilised by covalent binding through an array composed of carbon Toray paper as support and a layer of poly(methylene blue)/tetrabutylammonium bromide/Nafion and glutaraldehyde (3D bioanode electrode). The single MMFC was tested in a hybrid microfluidic fuel cell using Pt/C as the cathode. A cell voltage of 1.035 V and power density of 3.154 mW cm−2 were observed, which is the highest performance reported to date. The stability and durability were tested through chronoamperometry and polarisation/performance curves obtained at different days, which demonstrated a slow decrease in the power density on day 10 (14%) and day 20 (26%). Additionally, the cell was tested for ethanol oxidation in simulated body fluid (SBF) with ionic composition similar to human blood plasma. Those tests resulted in 0.93 V of cell voltage and a power density close to 1.237 mW cm−2. The double cell MMFC (Stack) was tested using serum and human blood enriched with ethanol. The stack operated with blood in a serial connection showed an excellent cell performance (0.716 mW cm−2), demonstrating the feasibility of employing human blood as energy source.