Lee also successfully measured the local voltage and temperature in a PEMFC using micro voltage and temperature sensors selleck compound [15]. The present investigation proposes a novel method for fabricating flexible multi-functional micro sensors of voltage, temperature and humidity on a stainless steel foil substrate using micro-electro-mechanical systems (MEMS). Home-made flexible multi-functional micro sensors have numerous advantages, including high temperature resistance, smallness, high sensitivity, and precision of measurement position. Flexible multi-functional micro sensors were embedded in a cathode flow channel of a PEMFC to measure and analyze variations in internal local voltage, temperature and humidity, and then to identify water flooding.2.?Theory and Design of Micro Sensors2.1.

Micro Voltage SensorThe voltage sensor that was Inhibitors,Modulators,Libraries used herein is a miniaturized voltage probe. Inhibitors,Modulators,Libraries This film-type probe is embedded inside a fuel cell to take measurements in particular locations. The sensing area of the voltage sensor, in contact with the bipolar plate of the fuel cell, is 200 ��m �� 200 ��m. The rest of the conducting wire is insulated. Figure 1 displays the micro voltage sensor.Figure 1.Design of the micro voltage sensor.2.2. Micro Temperature SensorThe temperature sensor utilized herein is a resistance temperature detector (RTD), which has the advantages of a large range of sensing temperatures and high linearity. The electrodes had serpentine structures, with a sensing area of 400 ��m �� 400 ��m, as shown in Figure 2.Figure 2.Design of the micro temperature sensor.

An Inhibitors,Modulators,Libraries increase in Inhibitors,Modulators,Libraries the environmental temperature increases the resistance of the RTD because a metal conductor has a positive temperature coefficient (PTC). When the temperature of the RTD varies in the linear region, the relationship between the measured resistance and the change in temperature can be expressed as:Rt=Rr (1+��T��T)(1)where Rt is the resistance at t ��C; Rr is the resistance at i ��C, and ��T is the sensitivity (1/��C) [16].2.3. Micro Humidity SensorWang measured the humidity of silicon nitride ceramics using a capacitive humidity sensor. The time to respond from high to low humidity was short [17]. Chang fabricated zinc oxide nanowires on a silicon chip, in the form of a resistive humidity sensor, to sense humidity [18]. However, in both approaches, the fabrication was highly complex and neither scheme is suitable for fuel cells.

Laconte fabricated a capacitive humidity sensor from a complementary metal-oxide semiconductor (CMOS). A coat of polyimide Dacomitinib was deposited on interdigitated electrodes. This approach greatly improved the sensitivity and response time of the sensors [19]. F��rjes fabricated a heater KPT-330 supplier around the humidity sensor, and his results revealed that the use of a heater shortened the measurement time from the original 15 minutes to 20 s [20].