Development of microfluidic fuel cell stack design and characterization of fuel cell stack performance are presented; these fuel cell stacks are mainly characterized by fuel reuse and cell performance employing a low concentration (0.25 M) and flow rates between 3 ml h(-1) and 9 ml h(-1), operating in parallel, series, or in a combination of both connections. Formic acid was used as the fuel, and oxygen from the air was used as the oxidant; the performance reached up to 6 mW of total power. Kirchhoffs law was used to explain the results obtained for the different possible system connections. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.