A miniature air-breathing direct formic acid fuel cell (DFAFC) based 4-cell stack, with a gold coated printed circuit board as the end plate and current collector, and with an independent fuel reservoir to avoid undesired interlaced electrolysis between different cells, is designed and investigated. Emphasis in the investigation is placed on design details, cell performance, dynamic response, and the stability of both the stack and individual cells. The striking difference in our cell configuration as compared with constructions reported in the literature is the existence of independent cavities as fuel reservoirs for each single cell. The outstanding merit of this particular design is the avoidance of water hydrolysis between electrodes, which is inevitable in stacks built with a shared fuel tank. A maximum power density of 56.6 mW cm(-2) is achieved and 5.0 M is considered as the optimum concentration for this 4-cell stack. A single cell can discharge at 20 mA for 70h with a voltage decline rate of only 2.7 mVh(-1) while sufficient formic acid is pumped into the cell. (C) 2011 Elsevier B.V. All rights reserved.