Guan-Wei Wu

Fabrication of micro temperature sensor on the flexible substrate

In this study, micro flexible temperature sensor arrays were designed and fabricated on parylene thin film. The flexible parylene thin film was inserted into the micro temperature sensors using the micro-electro-mechanical-systems (MEMS) fabrication process. The flexible micro sensor array was covered with two pieces of parylene thin film that was etched by reactive ion etching (RIE) to uncover the contact pad. Finally, the silicon wafer was segmented and then soaked in acetone to remove the flexible temperature sensor from the silicon substrate. In fabricating the thin films, Au and Cr resistive temperature sensor arrays with Al conducting lines, the Cr was formed the adhesion layer between parylene and Au. The thickness of parylene and the micro temperature sensor was 2 mum. They could therefore be easily attached to curved surfaces. The thin film sensors were highly sensitive (4.44times10-3/degC) to temperature and were effective at temperatures of up to 100degC. This study verified the feasibility of thin film sensor array applications with flexible parylene-base.

Novel Method for Measuring Temperature Distribution within Fuel Cell using Microsensors

A fuel cell has the potential to become an important source of electric power. However, measuring the temperature inside the fuel cell is difficult. Hence, in this investigation, an array of microsensors is set up inside the fuel cell to measure the temperature distribution. The substrate of a bipolar plate in the fuel cell is stainless steel (SS-316) and an electroforming technique is implemented to fabricate channels in the stainless steel substrate. Then micro-electro-mechanical system (MEMS) technologies are employed to fabricate a platinum temperature sensor on the rib of a channel in the stainless steel substrate. In this experiment, the temperature of microsensor is measured to range from 31 to 80 °C and its resistance ranges from 0.593 to 0.649 Ω. Experimental results demonstrate that temperature is almost linearly related to resistance and that accuracy and sensitivity are 0.5 °C and 1.93×10-3/°C, respectively. The performance curves of a single fuel cell operating at 34 °C and H2/O2 gas flow rates of 50/50 ml/min are determined. The maximum power density is 170 mW/cm2 and the current density is 513 mA/cm2.

in situ Measuring of Temperature and Humidity within the Membrane Electrode Assembly by Micro-Sensors

This study investigated the micro array sensors which were fabricated by micro-electro-mechanical-systems (MEMS) fabrication technology for monitoring the temperature and humidity distributions within the membrane electrode assembly (MEA) of fuel cells. The micro array sensors were embedded in parylene substrate, the sensors were made from chromium and gold. The advantages of micro temperature and humidity sensors are their small volume, which enables them to be placed on MEA with high sensitivity and accuracy. The dimensions of the temperature and humidity sensors are 180 µm × 180 µm and 180µm × 220µm, respectively. The operating conditions involve temperatures from 30 to 100°C and the resistance of temperature sensor varied from 31.685 to 36.798 Ω. The measuring results reveal that the temperature is almost linearly related to the resistance and the accuracy and sensitivity are less than 0.3°C and 2.3×10−3/°C. The humidity sensor showed that the capacitance changed from 12.14 to 15.03 pF, the relative humidity from 25 to 95 % RH, and the accuracy and sensitivity is less than 0.25 % RH and 0.04 pF/% RH.

A Novel Method for Measuring the Temperature Distribution Within the Fuel Cell Using Array Micro Sensors

The fuel cell has the potential to become an important source of electric power. However, measuring the temperature inside the fuel cell is difficult. Hence, in this investigation, array of micro sensors are set up inside a fuel cell to measure the temperature distribution. The substrate of the bipolar plate in a fuel cell is made of stainless steel (SS-316) and the electroforming technique is implemented to fabricate channels in the stainless steel substrate. Then NEMS (Micro-Electro-Mechanical Systems) technologies are employed to fabricate the platinum temperature sensor on the rib of a channel of stainless steel. The major advantages of array micro platinum temperature sensors are their small volume, high accuracy, short response time, simplicity in their fabrication, their mass production and ability to measure the temperature precisely and more effectively than a traditional thermocouple. The stainless steel bipolar plate is a good conductor of electric and heat. It has high mechanical strength and is non-porous. The graphite bipolar plate does not have such extensive advantages. This work electroforms a channel on stainless steel and then fabricates an array of micro temperature sensors on the rib of the channel. It is used to measure the temperature distribution at all locations in a fuel cell with a metallic bipolar plate. In the experiment, the temperature- is measured from 31 to 80 degrees Celsius and its resistance range from 0.593 to 0.649 ohm. The experimental results demonstrate that the temperature was almost linearly related to the resistance and the accuracy and sensitivity are under 1 degrees Celsius and 1.85×10−3 over degrees Celsius, respectively.© 2006 ASME