In this investigation, flexible sensors embedded in a membrane electrode assembly (MEA) are fabricated to measure the temperature and humidity of a micro-fuel cell. Fuel cell performance was determined by the temperature and humidity of the MEA. Restrictions on the sensor volume are such that in previous investigations the temperature and the humidity of the MEA have been measured only at the fuel inlet and outlet. Hence, flexible micro-thin film sensors were fabricated using micro-electro-mechanical systems (MEMS) fabrication technology. The thin film flexible sensor was 2 pm thick. The temperature and humidity sensors had areas of 180 mu m x 180 mu m and 180 mu m x 220 mu m, respectively. A flow channel was integrated in a stainless-steel base (SS-304) with micro-channels that are 300 mu m wide and 200 mu m deep using wet-etching technology. This study reveals the feasibility of utilizing flexible thin film sensors with micro-fuel cells to measure local temperature and humidity in an MEA. We found that the maximum temperature difference between MEA and the outer surface of a bipolar plate is 5.7 degrees C. The optimal performance curves of the single cell are obtained at 50 degrees C, 75%RH and H-2/O-2 gas flow rates of 50 ml min(-1). The maximum power density of the fuel cell was 358 mW cm(-2) and the current density was 796 mA cm(-2) when the cell voltage was 0.45 V. (c) 2008 Elsevier B.V. All rights reserved.