Stainless steel mesh (SSM) with four opening sizes (20-80 M) were investigated as matrixes of activated carbon air-cathodes in microbial fuel cells (MFCs). The highest power density of 2151 +/- 109 mW m(-2) (at 5.54 +/- 0.14 A m(-2)) was obtained using 40 M, with a value 45% higher than 1485 +/- 18 mW m(-2) of 80 M. The trend of linear sweep voltammetries were in accordant with power output over a cathodic potential range from -0.2 to 0 V. The differences in performance were attributed to the internal resistances. Charge transfer resistance (R-ct) was the dominant internal resistance in most of air-cathodes, with the lowest value of 2 52 in 40 M. Density of metal mesh exhibited a more significant correlationship with maximum power densities (R-2 = 0.9222) compared to opening size (R-2 = 0.7068), demonstrated that the density of metal current collector was vital to the performance of cathodes. (C) 2014 Elsevier Ltd. All rights reserved.